Monday, February 29, 2016

By Dr. Bissell MD & Dr Bruce Wang & Jennifer Lai MD Overview of HCP & VP Facts

Hereditary Coproporphyria

, MD, , MD, and , MD.
Initial Posting: ; Last Update: July 1, 2015.

Summary

Clinical characteristics.

Hereditary coproporphyria (HCP) is an acute (hepatic) porphyria in which the acute symptoms are neurovisceral and occur in discrete episodes. Attacks typically start in the abdomen with low-grade pain that slowly increases over a period of days (not hours) with nausea progressing to vomiting. In some individuals, the pain is predominantly in the back or extremities. When an acute attack is untreated, a motor neuropathy may develop over a period of days or a few weeks. The neuropathy first appears as weakness proximally in the arms and legs, then progresses distally to involve the hands and feet. Some individuals experience respiratory insufficiency due to loss of innervation of the diaphragm and muscles of respiration. Acute attacks are associated commonly with use of certain medications, caloric deprivation, and changes in female reproductive hormones. About 20% of those with an acute attack also experience photosensitivity associated with bullae and skin fragility.

Diagnosis/testing.

The most sensitive and specific biochemical  test for any one of the acute porphyrias (including HCP) during an acute attack is a striking increase in urinary porphobilinogen (PBG). Quantitative analysis of porphyrins in both urine and feces is essential to distinguish between the different acute porphyrias and establish the diagnosis of HCP. Identification of a heterozygous pathogenic variant in CPOX (encoding the enzyme coproporphyrinogen-III oxidase) confirms the diagnosis and enables family studies.

Management.

Treatment of manifestations: Acute attacks are treated by discontinuation of any medications thought to induce attacks, management of dehydration and/or hyponatremia, administration of carbohydrate, and infusion of hematin. Treatment of symptoms and complications should be with medications known to be safe in acute porphyria (see www.drugs-porphyria.org).
A minority of  individuals experience repeat acute attacks, in which case management strategies include suppression of ovulation in females, prophylactic use of hematin, and liver transplantation when attacks and neurologic complications persist despite multiple courses of hematin.
Prevention of primary manifestations: Agents or circumstances that may trigger an acute attack (including use of oral contraception in women) are avoided. Suppression of menses using a GnRH agonist (leuprolide, nafarelin, and others) may help CPOX heterozygotes who experience monthly exacerbations.
Prevention of secondary complications: In CPOX heterozygotes undergoing surgery, intravenous glucose is provided in the perioperative period and non-barbiturate agents are used for induction of anesthesia.
Agents/circumstances to avoid: Fasting, use of female reproductive hormones, and certain drugs including barbiturates and phenytoin.
Evaluation of relatives at risk: If the family-specific CPOX pathogenic variant is known, clarification of the genetic status of relatives at risk allows early diagnosis of heterozygotes and education regarding how to avoid risk factors known to be associated with acute attacks.

Genetic counseling.

HCP is inherited in an  manner with reduced . Most individuals with HCP have an  parent; the proportion with a de novo pathogenic variant is unknown. Each child of an individual with HCP has a 50% chance of inheriting the CPOX pathogenic variant. Because of reduced penetrance, many individuals with a CPOX pathogenic variant have no signs or symptoms of HCP. Prenatal diagnosis for pregnancies at increased risk is possible if the pathogenic variant in an affected family member is known.

Diagnosis

Hereditary coproporphyria (HCP) is classified as both an acute (hepatic) porphyria (with neurologic manifestations that occur as discrete, severe episodes) and a chronic (cutaneous) porphyria with long-standing photosensitivity.

Suggestive Findings

Acute hepatic porphyria is suspected in individuals with the following symptoms or findings:
  • Nausea for at least 48 hours
  • Abdominal, back, or extremity pain for at least 48 hours
  • New-onset seizures
  • Hyponatremia
    Note: Although CPOX pathogenic variants occur equally in males and females, acute attacks are much more frequent in women, mainly between ages 16 and 45 years (the years of active ovulation).
Chronic cutaneous porphyria is suspected in individuals with bullae and fragility of light-exposed skin which result in depigmented scars; however, the cutaneous signs occur in only a minority of heterozygotes, even during an acute attack.

Establishing the Diagnosis

The diagnosis of HCP is established by either biochemical testing (Table 1) or identification of a heterozygous pathogenic variant in CPOX on  (Table 2).

Biochemical Testing

For an individual with pain and neurologic signs, the initial goal is to determine if the symptoms can be attributed to an attack related to any one of the acute porphyrias (i.e., ALA dehydratase deficiency porphyria, acute intermittent porphyria, hereditary coproporphyria, or variegate porphyria) (see Differential Diagnosis). Note: Since initial management is the same for all four types of acute porphyria, it is not necessary to determine at the outset of treatment which one of the four types of acute porphyria is present.
The most sensitive and specific biochemical diagnostic tests for HCP are detailed in Table 1. Once the diagnosis of an acute porphyria is established by identification of a striking increase in urinary porphobilinogen (PBG), quantitative analysis of porphyrins in both urine and feces may help define the specific type (Figure 1).
Figure 1. . Excretion profile of the hepatic porphyrias 

Profile of heme precursor excretion for the types of hepatic porphyria.

Figure 1.

Excretion profile of the hepatic porphyrias

Profile of heme precursor excretion for the types of hepatic porphyria. The pathway of heme synthesis (arrows) is served by a series of enzymes (boxes). Mutations that decrease the function (more...)
  • Active HCP is suggested by a quantitative urinary porphobilinogen (PBG) that is at least threefold the upper limit of normal.
  • The characteristic finding in stool is COPRO >> PROTO, quantified as units/g dry weight of feces. Note: Some laboratories report units/24 hours, which is inherently inaccurate. US laboratories that do the more precise analysis include ARUP (Salt Lake City, UT) and the Porphyria Laboratory, University of Texas Medical Branch, K Anderson, MD, Director (Galveston, TX).
  • The diagnosis is further substantiated by analysis of the COPRO-III/COPRO-I fecal porphyrin ratio, showing that 60%-95% of the total COPRO is isomer-III. In a normal (or ‘negative’) test, the predominant fecal porphyrin is PROTO, and the COPRO isomer III/I ratio in many cases is <0.5 [].

Table 1.

Biochemical Characteristics of Hereditary Coproporphyria (HCP)
Deficient EnzymeUrineStool
ActiveAsxActiveAsx
Coproporphyringen-III oxidase 1, 2↑PBG 3, 4
↑COPRO 5
Normal PBG
COPRO 6
COPRO >> PROTO 7See footnote 8
Active = symptomatic CPOX heterozygotes
Asx = asymptomatic CPOX heterozygotes
PBG = porphobilinogen
NormaI PBG = <2 mg (0.85 μmol) per g urine creatinine
COPRO = coproporphyrin
PROTO = protoporphyrin
1.
Also known as coproporphyrinogen oxidase and coproporphyrinogen decarboxylase
2.
The  is not widely available and is not used for diagnostic purposes
3.
Active HCP is suggested by a quantitative urine PBG that is at least 3-fold the upper limit of normal
4.
Commercial laboratories offer quantitative delta aminolevulinic acid (ALA), PBG, and fractionated urine porphyrins. Values normalized to urine creatinine are satisfactory for clinical use, making a 24-hour collection unnecessary.
5.
See Differential Diagnosis for discussion of nonspecific elevation of COPRO in the urine.
6.
Fractionated urine porphyrins may reveal a minor rise in COPRO (<3-fold the upper limit of normal); however, this is nonspecific and insufficient for diagnosis (see Differential Diagnosis).
7.
60%-95% of the total COPRO is isomer-III.
8.
Fecal porphyrin analysis is the best test for distinguishing HCP from nonspecific coproporphyrinuria: heterozygotes show a predominance of fecal COPRO and an elevated COPRO III/I ratio (see Biochemical Testing).

Molecular Genetic Testing

Molecular testing approaches start with single- testing targeting the type of acute porphyria suggested by biochemical testing.
  • Sequence analysis of CPOX is performed first, followed by -targeted  if no pathogenic variant is found.
  • If detailed CPOX testing is negative, PPOX (the  for variegate porphyria [VP]) is analyzed. The biochemical findings in HCP and VP can overlap, leading to misassignment of diagnosis in some instances.

Table 2.

Summary of Molecular Genetic Testing Used in Hereditary Coproporphyria
Gene 1Test MethodProportion of Probands with a Pathogenic Variant 2 Detectable by This Method
CPOXSequence analysis 329/31 4
Gene-targeted  5See footnote 6
1.
See Table A. Genes and Databases for   and protein.
2.
See Molecular Genetics for information on allelic variants detected in this .
3.
Sequence analysis detects variants that are benign, likely benign, of uncertain significance, likely pathogenic, or pathogenic. Pathogenic variants may include small intragenic deletions/insertions and missense, nonsense, and splice site variants; typically, or whole- deletions/duplications are not detected. For issues to consider in interpretation of  results, click here.
4.
Sequence analysis identified a pathogenic variant in 29 of 31 (94%) individuals with the clinical and biochemical diagnosis of HCP [].
5.
Gene-targeted  detects intragenic deletions or duplications. Examples of methods that may be used include: , long-range PCR, multiplex ligation-dependent  amplification (MLPA), and -targeted microarray designed to detect single- deletions or duplications.
6.
A 13-kb  extending from  4 to the 3’UTR [] and a 1.3-kb deletion spanning exon 5 (found in four Swedish families) [] have been published.

Clinical Characteristics

Clinical Description

Hereditary coproporphyria (HCP) is classified as both an acute and chronic porphyria. Porphyrias with neurologic manifestations are considered acute, because the symptoms occur as discrete, severe episodes. Porphyrias with cutaneous manifestations are considered chronic, because photosensitivity is long standing (see Table 3).
In a German study of 46 individuals with acute HCP, 90% had abdominal pain; only 13% had cutaneous findings despite substantial overproduction of coproporphyrin []. An earlier British study of 111 individuals with HCP reported similar findings [].
Symptoms prior to puberty in individuals who are heterozygous for a CPOX pathogenic variant have never been observed.
Fertility and longevity do not appear to be reduced in CPOX heterozygotes.

Acute Attacks

The initial symptoms of an acute attack are nonspecific, consisting of low-grade abdominal pain that slowly increases over a period of days (not hours) with nausea progressing to vomiting of all oral intake.
Typically the pain is not well-localized but in some instances does mimic acute inflammation of the gallbladder, appendix, or other intra-abdominal organ. In most instances the abdominal examination is unremarkable except for diminished bowel sounds consistent with ileus, which is common and can be seen on abdominal radiography. Typically fever is absent. In a young woman of reproductive age, the symptoms may raise the question of early pregnancy.
Prior to the widespread use of abdominal imaging in the emergency room setting, some individuals with abdominal pain and undiagnosed acute porphyria underwent urgent exploratory surgery. Thus, a history of abdominal surgery with negative findings was considered characteristic of acute porphyria.
A minority of  individuals has predominantly back or extremity pain, which is usually deep and aching, not localized to joints or muscle groups.
Neurologic manifestations. Seizures may occur early in an attack and be the problem that brings the patient to medical attention. In a young woman with abdominal pain and new-onset seizures, it is critical to consider acute porphyria because of the implications for seizure management (see Management).
When an attack is unrecognized as such or treated with inappropriate medications, it may progress to a motor neuropathy, which typically occurs many days to a few weeks after the onset of symptoms. The neuropathy first appears as weakness proximally in the arms and legs, then progresses distally to involve the hands and feet. Neurosensory function remains largely intact.
In some individuals the motor neuropathy eventually involves nerves serving the diaphragm and muscles of respiration. Ventilator support may be needed.
Tachycardia and bowel dysmotility (manifest as constipation) are common in acute attacks and believed to represent involvement of the autonomic nervous system.
Of note when the acute attack is recognized early and treated appropriately (see Management), the outlook for survival and eventual complete recovery is good.
Psychosis. The mental status of people presenting with an acute attack of porphyria varies widely and can include psychosis. Commonly, however, the predominant feature is distress (including pain) that may seem hysterical or feigned, given a negative examination, absence of fever, and abdominal imaging showing some ileus only. Incessant demands for relief may be interpreted as drug-seeking behavior.
Because of the altered affect in acute porphyria, it has been speculated that mental illness is a long-term consequence of an attack and that mental institutions may house a disproportionately large numbers of individuals with undiagnosed acute porphyria. Screening of residents in mental health facilities by urinary PBG and/or PBG deaminase activity in blood (which diagnoses acute intermittent porphyria) has been done, with mixed results []. The experience of those who have monitored patients over many years suggests that heterozygotes who are at risk for one of the acute porphyrias are no more prone to chronic mental illness than the general population; however, a prospective study is needed.
Kidney and liver disease. In people with any type of acute porphyria, the kidneys and liver may develop chronic changes that often are subclinical. One manifestation of the liver problem is excess primary liver cancer (hepatocellular carcinoma), which arises mainly after age 60 years. This and the kidney disease may be restricted largely to heterozygotes with chronically elevated plasma or urine delta aminolevulinic acid (ALA).
Inasmuch as ALA and porphobilinogen (PBG) tend to be minimally elevated or normal in HCP heterozygotes, the risk of hepatic and renal complications may be less in HCP than in acute intermittent porphyria.
Circumstances commonly associated with acute attacks are caloric deprivation, changes in female reproductive hormones, and use of porphyria-inducing medications or drugs:
  • Caloric deprivation. Fasting appears to sensitize the heme-synthetic pathway to an inducer, which could be external (i.e., a medication) or internal (ovarian hormones). The sensitizing effect of caloric deprivation was demonstrated in the 1960s in experimental animals and has been confirmed by clinical observation. People who fail to eat because of intercurrent illness or who undertake drastic weight loss are predisposed to an acute attack. First attacks have been reported after reduction gastroplasty for obesity []. CPOXheterozygotes undergoing surgery are at risk because of the routine preoperative fast. This and other anecdotal experience have led to consensus that the first line of treatment for an acute attack is intravenous glucose, which is occasionally helpful.
  • Changes in female reproductive hormones. A role for female reproductive hormones can be inferred from the fact that acute attacks are infrequent prior to menarche and after menopause. Some women have monthly attacks that appear a few days before the onset of menstruation (when progestins peak). Attacks have been linked to use of oral contraceptives; the risk may be associated more with the progesterone component than the estrogen component.
  • Use of porphyria-inducing medications or drugs. See Management, Agents/Circumstances to Avoid.
Chronic (cutaneous) manifestations. Photocutaneous damage is present in only a small minority of those with acute attacks. Bullae and fragility of light-exposed skin, in particular the backs of the hands, result in depigmented scars. Facial skin damage also occurs, with excess hair growth on the temples, ears, and cheeks; this is more noticeable in women than in men.
The cutaneous findings in HCP resemble those in porphyria cutanea tarda (PCT) and in variegate porphyria (VP).
Threshold for a pathogenic effect of porphyrins and their precursors. Clinically active acute porphyria is associated with substantial elevation of the precursors ALA and PBG in the blood and urine; the cutaneous porphyrias are associated with increased porphyrins in blood, urine, and feces. In the acute porphyrias and cutaneous porphyrias, a threshold for symptoms appears to exist.
  • Acute (hepatic) porphyrias. A threshold for acute attacks is suggested by the fact that in virtually all symptomatic individuals, urinary PBG excretion exceeds 25 mg/g creatinine, or more than tenfold the upper limit of normal. Urinary ALA excretion increases roughly in parallel.
  • In contrast, in asymptomatic individuals the baseline urinary PBG excretion varies widely, usually low or normal but occasionally exceeding 25 mg/g creatinine. For this reason, it is advisable to establish the baseline urinary PBG excretion for CPOX heterozygotes (see Management, Evaluations Following Initial Diagnosis).
  • Chronic (cutaneous) porphyrias. A threshold has been well defined for porphyria cutanea tarda (PCT), in which photosensitivity occurs at values of urine uroporphyrin (the predominant pathway intermediate) that are more than 20-fold the upper limit of normal. However, the same is not apparent with regard to urine coproporphyrin: only a minority of CPOX heterozygotes exhibit any photosensitivity.

    Of note, in individuals with HCP and chronic liver disease the cutaneous component may be more prominent than expected for the observed urine or plasma PBG concentration. Coproporphyrin leaves the plasma largely via the liver going into bile. In chronic liver disease, bile transport processes or bile formation may be impaired, leading to accumulation of coproporphyrin in plasma, which then results in photosensitivity.

Pathophysiology

Although the bone marrow actively produces heme (for hemoglobin synthesis), the liver is the main source of precursors in the acute (hepatic) porphyrias: acute attacks are precipitated when environmental factors stimulate increased hepatic heme synthesis and the genetically altered step in heme production becomes rate-limiting (Figure 1). Heme synthesis in the liver largely serves production of the cytochrome P450 family of heme-proteins, which are present in high concentration in the liver and have a relatively high turnover rate.
It is estimated that 20%-25% of total heme production normally occurs in the liver []; however, that proportion increases when the liver is exposed to xenobiotics that undergo oxidative metabolism and stimulate cytochrome production (especially CYP3A4).
Acute attacks. The precursors ALA and PBG, unlike porphyrins, are colorless and non-fluorescent and do not contribute to photosensitivity in porphyria. Rather, ALA and PBG are highly associated with the neurologic manifestations of acute porphyria and are probably causal, although the mechanism remains speculative. The currently favored hypothesis implicates ALA (more than PBG), in part because acute neurologic symptoms occur in two other inherited conditions involving overproduction of ALA but not PBG (delta aminolevulinic acid dehydratase deficiency porphyria (ADP) and tyrosinemia). In addition, lead poisoning causes a similar biochemical derangement by binding the sulfhydryls of ALA dehydratase and reducing enzymatic activity; the symptoms in lead poisoning closely mimic those of acute porphyria []. Experimental studies indicate that ALA is a pro-oxidant species that is capable of damaging the inner membrane of mitochondria [].
Organ transplantation has established that the liver is responsible for acute attacks. Liver transplantation has cured individuals with refractory acute symptoms []. Moreover, transplantation of a porphyric liver into a normal recipient resulted in high circulating levels of ALA and PBG and symptoms of porphyria [].
Cutaneous manifestations. Porphyrins are energized by blue light (peak wave length 410 nm). In a test tube, as activated porphyrins relax back to the ground state the released energy is evident as red fluorescence (ca. 625 nm). In vivo, the cycle of light activation and relaxation back to the ground state causes tissue damage, the nature of which varies with the porphyrin. URO and COPRO give rise to bullae and fragility of light-exposed skin, in particular the backs of the hands.

Genotype-Phenotype Correlations

HCP. CPOX pathogenic variants are not clustered around the enzymatic site. Furthermore, no correlation exists between the clinical  and the residual enzymatic activity measured in vitro for a given pathogenic variant [].
Homozygotes for CPOX pathogenic variants that cause minimal or no symptoms in heterozygotes have been reported to have very low coproporphyringen-III oxidase activity and a severe  [] (see Genetically Related Disorders).
Double heterozygosity for pathogenic variants in genes causing two different types of acute (hepatic) porphyria.Double heterozygotes for a pathogenic variant in CPOX and either a pathogenic variant in PPOX (variegate porphyria[VP]) [] or ALAD (ALA dehydratase deficiency porphyria [ADP]) [] have been described. The phenotypes of such double heterozygotes vary but are not necessarily more severe than those associated with heterozygosity for either pathogenic variant alone, suggesting that double heterozygotes for two different types of acute porphyria may not be as rare as has been assumed.

Penetrance

Because population studies to determine the prevalence of HCP heterozygosity have not been done, the  ofCPOX pathogenic variants is unknown. Given the rarity of acute attacks of HCP relative to acute intermittent porphyria (AIP), it is suspected that only a small minority of CPOX heterozygotes express the clinical disease. In 32 members of an Australian family, 14 (including 10 adults) were determined to have HCP on the basis of a high fecal COPRO III/I ratio and/or low lymphocyte CPOX enzyme activity; however, only one had clinical symptoms of porphyria [].
HCP, along with AIP and VP, are genetic disorders with reduced . Heme production in most heterozygotes appears to be adequate for physiologic homeostasis. Thus, environmental or physiologic factors play a role in the pathogenesis of acute attacks (see Management, Agents/Circumstances to Avoid). Although genetic co-factors may also be involved, none has been identified to date.

Nomenclature

‘Coproporphyria’ describes urine with an elevated level of coproporphyrin of any cause.
Coproporphyria in individuals heterozygous for a CPOX pathogenic variant is referred to as hereditary coproporphyria.

Prevalence

Clinical experience suggests that HCP is the least prevalent of the three principal types of acute porphyria: AIP, VP, and HCP. However, symptoms in HCP may be less frequent than in AIP or VP. Population surveys for CPOX pathogenic variants have not been reported.

Differential Diagnosis

The genetic porphyrias comprise a group of distinct diseases, each resulting from alteration of a specific step in the heme synthesis pathway that results in accumulation of a specific substrate (Figure 1).
In Table 3 the porphyrias are grouped by their principal clinical manifestations (neurolovisceral or cutaneous) and the tissue origin of the excess production of pathway intermediates (liver [i.e., hepatic] or bone marrow [i.e., erythropoietic]).
  • Porphyrias with neurovisceral manifestations are considered acute because the symptoms occur as discrete, severe episodes, which may be spontaneous but frequently are induced by external factors. The four acute porphyrias are: ALA dehydratase-deficiency porphyria (ADP), acute intermittent porphyria (AIP), HCP, and variegate porphyria (VP). Only a few individuals with ADP have been reported in the world literature.
  • Porphyrias with cutaneous manifestations include either chronic blistering skin lesions (i.e., VP as well as PCT, HCP, CEP, and hepatoerythropoietic porphyria [HEP]) or acute non-blistering photosensitivity (i.e., EPP and XLP).

Table 3.

Classification of the Hereditary Porphyrias
Type of PorphyriaFindingsMode of Inheritance
Neurovisceral 1Photocutaneous
Hepatic
ADP+0AR
AIP+0AD
HCP++AD
PCT type II0+AD
VP++AD
Erythropoietic
CEP0+AR
EPP, AR02AR
XLP02XL
ADP = ALA dehydratase-deficiency porphyria
AIP = acute intermittent porphyria
HCP = hereditary coproporphyria
PCT = porphyria cutanea tarda
VP = variegate porphyria
CEP =  erythropoietic porphyria
EPP = erythropoietic protoporphyria
XLP = X-Linked protoporphyria
0 = no symptoms
+
= mild to severe symptoms
XL = X-linked
1.
Porphyrias with neurovisceral manifestations have been considered ‘acute’ in part because the most common of these disorders, named “acute intermittent porphyria,” is the prototype for the neurovisceral porphyrias in which symptoms can occur acutely as discrete, severe episodes; however, some  individuals develop chronic manifestations, and a few remain susceptible to exacerbating factors throughout their lives.
2.
Photocutaneous manifestations of EPP are acute and non-blistering, in contrast to the chronic blistering in the other cutaneous porphyrias (including VP).
While these clinical distinctions are important for the differential diagnosis, biochemical analysis is always necessary; however, biochemical testing may fail to distinguish HCP from VP, in which case  of CPOX(HCP) and PPOX (VP) may be the only definitive diagnostic test.
In individuals with progressive weakness due to the motor neuropathy caused by one of the acute porphyrias (AIP, VP, HCP, and ADP), the entity most likely to be considered is acute ascending polyneuropathy, the Guillain-Barré syndrome. However, abdominal pain, constipation, and tachycardia precede the acute neurologic illness in the acute porphyrias but not in Guillain-Barré syndrome. CSF protein is normal in the acute porphyrias, but elevated in Guillain-Barré syndrome. Urinary PBG is markedly elevated in the acute porphyrias when symptoms are present, but normal in Guillain-Barré syndrome.
Coproporphyrinuria
  • Lead intoxication. The predominant elevation of coproporphyrin that is characteristic of HCP can also be seen in lead intoxication, in which the symptoms resemble those of an acute porphyria. The additional diagnostic finding in heavy metal poisoning is elevation of ALA unaccompanied by any increase in PBG.
  • Rotor syndrome, inherited in an  manner and caused by simultaneous deficiencies of the organic anion transporting polypeptides OATP1B1 and OATP1B3, is also associated with coproporphyrinuria [].
  • Nonspecific coproporphyrinuria. The most important differential diagnosis in an individual with elevated urine coproporphyrin is HCP vs nonspecific coproporphyrinuria. Of all the people referred to a porphyria center, the largest subgroup has nonspecific coproporphyrinuria. Elevation of urine coproporphyrin is associated with a wide range of clinical conditions. It is particularly frequent in acquired liver disease (e.g., chronic viral hepatitis), but can also be seen in neurologic or hematologic diseases. Rarely, it is caused by an inherited hepatic transporter defect.

    Two tests helpful for the differential diagnosis of coproporphyrinuria are:
    • Urine PBG, which is more than tenfold elevated in the inherited acute porphyrias with active symptoms;
    • The ratio of copro-III to copro-I in feces as measured by high-performance liquid chromatography (used for fecal porphyrin fractionation in most commercial labs). In nonspecific coproporphyrinuria the ratio is usually similar to that in normal controls [].
For a case example of misdiagnosis of nonspecific coproporphyrinuria, click here.

Management

Evaluations Following Initial Diagnosis

To establish the extent of disease and needs of an individual diagnosed with hereditary coproporphyria (HCP), the following evaluations are recommended in an individual with acute abdominal symptoms:
  • Review of medications for those that are thought to induce attacks (See Agents/Circumstances to Avoid.)
  • Detailed neurologic examination for signs of motor neuropathy (which indicates a more advanced attack and, therefore, the need for early treatment with hematin)
  • Inquiry into possibility of seizures
  • Measurement of serum sodium concentration. Hyponatremia is characteristic and may be profound (serum sodium concentration <110 mEq/L), requiring urgent correction with due regard for the risk of central pontine myelinolysis.
  • Quantitation of urinary excretion of porphobilinogen (PBG) on several occasions over a few months to establish a baseline for future use in determining if a new symptom or drug reaction is due to an acute attack (In an acute attack urinary excretion of PBG is substantially elevated over the baseline.)
  • Medical genetics consultation

Treatment of Manifestations

Acute Attacks

Further details on the treatment of acute porphyria are available in published reviews [].
In an individual presenting with acute abdominal symptoms:
  • Identify and discontinue any medications that are thought to induce attacks (see Agents/Circumstances to Avoid).
  • Discontinue all nonessential medications.
  • Evaluate those with nausea and vomiting for dehydration and hyponatremia, which is characteristic and may be profound (serum sodium concentration <110 mEq/L), requiring urgent correction with due regard for the risk of central pontine myelinolysis.
  • Provide glucose-containing IV solution to reverse the fasting state.
    Note: Caution is indicated in patients with hyponatremia, as aggressive administration of dextrose in water may cause the serum sodium concentration to drop to a critically low level.
  • Treat seizures with a short-acting benzodiazepine (e.g., midazolam) or with magnesium, which has been used for eclamptic seizures [].
    Note: A number of the commonly used anti-seizure medications, including phenytoin and sodium valproate, are contraindicated because of the risk of further exacerbating an attack (see Agents/Circumstances to Avoid).
  • Intravenous hematin is the treatment of choice in moderate to severe acute attacks. Order hematin at the time that an acute attack requires hospitalization. Although hematin is not stocked by most hospital pharmacies, it can be obtained by overnight express from the manufacturer (Panhematin®, Recordati, 1-888-575-8344). An alternative in Europe and elsewhere is heme arginate (Normosang®; not yet approved in the US).
    • Some individuals recover with a glucose infusion only; those who do not respond in 24 to 48 hours should receive intravenous hematin.
    • When signs of a motor neuropathy are present, hematin is given as soon as possible. Hematin given at the initial signs of motor neuropathy may halt its progression; however, it has no effect on established motor deficits, which are the result of axonal degeneration.
    • Hematin is reconstituted at the bedside as described in the package insert. Human albumin may be used in place of water (132 mL of a 25% albumin solution) to reduce the risk of a chemical phlebitis, which is the main side effect of hematin administration [].
      • The infusion is started without delay, as hematin in solution decays rapidly [].
      • The preparation is given into a large peripheral vein or via central line over 10-15 minutes so as to minimize the risk of phlebitis. The dose is weight based at 3-4 mg/kg; 200 mg once daily is appropriate for most individuals.
The following responses to hematin infusion can be expected:
  • Decrease in the urine concentration of PBG, the first sign, occurs after two doses.
  • Clinical improvement is seen after a total of three or four doses, and typically is dramatic, with no further need of narcotic analgesia [].
  • The motor neuropathy of acute attacks, when it occurs, does not respond to hematin administration. Return of function requires axonal regeneration and takes many months. Although it can be complete, some individuals have residual wrist drop or foot drop.
Liver transplantation. The experience with liver transplantation in acute porphyria is growing, with accumulating evidence that transplantation is curative in selected severe cases []. The status of the disease in candidates for liver transplantation must be well-documented biochemically: they must not have responded to multiple courses of hematin and must be demonstrating neurologic complications.

Chronic (Cutaneous) Manifestations

For low-grade chronic or seasonal cutaneous symptoms, the only effective current treatment is avoidance of sun/light, whether direct or through window glass. Damage is caused by blue light and long-wave ultraviolet light (UVA), both of which pass through window glass:
  • Sun protection using protective clothing such as long sleeves, gloves, and wide brimmed hats
  • Protective tinted glass for cars and windows to prevent exposure to blue light. Grey or smoke colored filters provide only partial protection.
Note: Topical sunscreens are not helpful because they block UVB light, not the blue light that causes porphyrin-related skin injury.
The association of cutaneous manifestations with severe attacks (in which porphyrins as well as ALA and PBG are markedly increased) suggests that the cutaneous, as well as the neurovisceral, symptoms could respond to hematin administration. Indeed, this is the finding of a recent case report of an individual with severe HCP who was given ‘maintenance’ hematin [].
Other. For more prolonged control of seizures, the combination of gabapentin and propofol is effective and safe.

Prevention of Primary Manifestations

Prevention of acute attacks involves the following:
  • Molecular genetic testing of at-risk relatives to identify those heterozygous for the CPOX pathogenic variant identified in the 
  • Education of CPOX heterozygotes regarding circumstances that may trigger an acute attack (See Clinical Description.)
  • Selection of appropriate contraception for females. Oral contraceptives (birth control pills) are risky and not recommended. The recommended method of birth control for HCP heterozygotes is an IUD plus a barrier (diaphragm and/or condom).
    • A copper-eluting IUD is theoretically the safest in porphyria.
    • The hormone-eluting variety may also be safe because the systemic increase in hormone is quite small; however, little information exists.
  • Suppression of menses using a GnRH agonist. Leuprolide, nafarelin, and other GnRH agonists may help CPOXheterozygotes who experience monthly exacerbations.
CPOX heterozygotes undergoing surgery are at increased risk for an acute attack because of the routine preoperative fast and the (former) use of barbiturate (thiopental) induction of anesthesia. Adherence to the following recommendations greatly reduces the risk of an acute attack:
  • Minimizing the preoperative fast as much as possible and providing intravenous glucose (10% dextrose in half-normal saline) in the perioperative period
  • Anesthesia induction using non-barbiturate agents that have little or no P450-inducing activity (e.g., propofol, ketamine, short-acting benzodiazepines). Inhalation agents (isoflurane) and muscle relaxants also appear to be low-risk for triggering an attack.
Prevention of acute attacks does not involve the following:
  • Use of glucose. Because glucose is used to treat acute attacks, its use in preventing attacks has been suggested, and is in fact touted in lay discussions of porphyria; however, there is no evidence that heterozygotes can protect themselves by overeating or adopting a high-carbohydrate diet, and they risk becoming obese. Heterozygotes should adhere to a healthful diet with the usual balance of protein, fat, and carbohydrate. Weight loss is possible but only by incremental restriction of calories combined with exercise. Extreme diets (e.g., all bacon, all brown rice, starvation) are risky and should be avoided.
  • Liver transplantation. Because the vast majority of attacks respond to hematin and other supportive measures, liver transplantation has no role in prevention of acute attacks in a CPOX .

Surveillance

For those who have chronically elevated ALA (which is infrequent in those who are asymptomatic) and/or are older than age 60 years, an annual check of liver and kidney function is recommended.
Current noninvasive techniques for assessment of fibrosis in the liver include transient elastography (FibroScan®) and a blood-based test (FibroTest® or FibroSure®). Note: They have been vetted mainly for people with chronic viral hepatitis or steatohepatitis but may also be useful in porphyria.
For anyone with evidence of chronic liver injury, annual  for hepatocellular carcinoma with abdominal imaging (such as ultrasound) and serum alpha-fetoprotein is indicated.

Agents/Circumstances to Avoid

Avoid the following:
  • Extreme caloric deprivation (i.e., total fasting, gastric bypass surgery)
  • Female reproductive hormones. Birth-control pills are risky and not recommended. For recommendations regarding contraception, see Prevention of Primary Manifestations, Selection of appropriate contraception for females.
  • Medications. Some drugs are clearly unsafe for CPOX heterozygotes. It is important to note, however, that many drugs are safe, lest providers regard individuals with acute porphyria as “untreatable.” Compilations of safe and unsafe drugs are available online and are updated as new information becomes available. Seewww.porphyriafoundation.com and www.porphyria-europe.com.

    In theory, the most dangerous medications are inducers of CYPs, such as barbiturates and the related compound, phenytoin.

Evaluation of Relatives at Risk

It is appropriate to evaluate relatives at risk for HCP in order to identify as early as possible those who would benefit from education regarding the risk factors associated with acute attacks.
  • If the CPOX pathogenic variant in the family is known,  can be used to clarify the genetic status of at-risk relatives.
  • If the CPOX pathogenic variant in the family is not known, a  with symptoms can be evaluated with biochemical tests (see Diagnosis). Note: Although some CPOX heterozygotes have a diagnostic biochemical profile of heme precursors in urine and feces (see Table 1, ‘Active’ columns), many have normal findings (see Table 1, ‘Asymptomatic’ columns) and can only be diagnosed by .
See Genetic Counseling for issues related to testing of at-risk relatives for  purposes.

Pregnancy Management

The effect of pregnancy on inducing acute attacks is unpredictable. In general, serious problems during pregnancy are unusual. In fact, some women with recurrent symptoms associated with the menstrual cycle report improvement during pregnancy. Attacks, if they occur, are usually in the first trimester. The women most at risk are those with hyperemesis gravidarum and inadequate caloric intake []. Among antiemetics, ondansetron is not expected to precipitate or exacerbate acute attacks or to increase the risk for  anomalies in the fetus; however, metoclopramide should be avoided, as it may precipitate acute attacks [].
The experience with administration of hematin (or heme arginate, which is not available in the US) during pregnancy is limited.  published an anecdotal report of successful heme arginate treatment (without adverse fetal effect) in several women experiencing attacks of variegate porphyria or other acute porphyrias during pregnancy. Based on the absence of reported adverse effects, use of hematin to control exacerbations of acute intermittent porphyria during pregnancy has been recommended [].

Therapies Under Investigation

Due to the rarity of symptomatic acute porphyria, the efficacy of intravenous hematin has never been documented in a controlled trial. Efforts to accomplish this are under way.
Planned studies focus on individuals who have spontaneous acute attacks in the absence of any known external trigger in order to identify genetic cofactors that may be involved in such attacks, and are thus potential targets for new therapies.
Search ClinicalTrials.gov for access to information on clinical studies for a wide range of diseases and conditions.

Genetic Counseling

Genetic counseling is the process of providing individuals and families with information on the nature, inheritance, and implications of genetic disorders to help them make informed medical and personal decisions. The following section deals with genetic risk assessment and the use of family history and genetic testing to clarify genetic status for family members. This section is not meant to address all personal, cultural, or ethical issues that individuals may face or to substitute for consultation with a genetics professional. —ED.

Mode of Inheritance

Hereditary coproporphyria (HCP) is inherited in an  manner.

Risk to Family Members

  • Most individuals with HCP have an  parent.
  •  with HCP may harbor a de novo CPOX pathogenic variant. The proportion of HCP caused by a de novo pathogenic variant is unknown.
  • Recommendations for the evaluation of parents of a  with an apparent de novo pathogenic variant include for the CPOX pathogenic variant identified in the proband.
  • Evaluation of parents may determine that one has a CPOX pathogenic variant but has not been previously diagnosed because of reduced . Therefore, an apparently negative  cannot be confirmed until  has been performed.
Sibs of a 
  • The risk to the sibs of the  depends on the genetic status of the proband’s parents.
  • If a parent of the  is heterozygous for the CPOX pathogenic variant identified in the proband, the risk to the sibs of inheriting the CPOX pathogenic variant is 50%. Because of reduced , many individuals heterozygous for a CPOX pathogenic variant do not manifest signs and symptoms of HCP.
  • If the CPOX pathogenic variant found in the  cannot be detected in either parent, the risk to sibs is low but greater than that of the general population because of the possibility of .
Offspring of a . Each child of an individual with HCP has a 50% chance of inheriting the CPOX pathogenic variant. Because of reduced , many individuals with a CPOX pathogenic variant do not manifest signs and symptoms of HCP.
Other family members
  • The risk to other family members depends on the status of the 's parents.
  • If a parent is heterozygous for a CPOX pathogenic variant, his or her family members may be at risk.

Related Genetic Counseling Issues

See Management, Evaluation of Relatives at Risk for information on evaluating at-risk relatives for the purpose of early diagnosis and treatment.
Considerations in families with an apparent de novo pathogenic variant. When neither parent of a  with HCP has the CPOX pathogenic variant or clinical evidence of the disorder, the CPOX pathogenic variant is likely de novo. However, non-medical explanations including  or maternity (e.g., with assisted reproduction) or undisclosed adoption could also be considered.
Testing of at-risk asymptomatic relatives of individuals with HCP is possible after  has identified the specific CPOX pathogenic variant in the family. Such testing should be performed in the context of formal. The results of molecular genetic testing are not useful in predicting age of onset, severity, or specific symptoms. Note: Although some CPOX heterozygotes have a diagnostic biochemical profile of heme precursors in urine and feces (see Table 1, ‘Active’ columns), many have normal biochemical test results (see Table 1, ‘Asymptomatic’ columns) and can be diagnosed only by molecular genetic testing.
Family planning
  • The optimal time for determination of genetic risk and discussion of the availability of prenatal testing is before pregnancy.
  • It is appropriate to offer  (including discussion of potential risks to offspring and reproductive options) to young adults who are  or at risk.
 is the storage of DNA (typically extracted from white blood cells) for possible future use. Because it is likely that testing methodology and our understanding of genes, allelic variants, and diseases will improve in the future, consideration should be given to banking DNA of  individuals.

Prenatal Testing

If the CPOX pathogenic variant has been identified in an  family member, prenatal testing for pregnancies at increased risk may be available from a clinical laboratory that offers either testing of this  or .
Differences in perspective may exist among medical professionals and within families regarding the use of prenatal testing, particularly if the purpose is pregnancy termination rather than early diagnosis. Parents are encouraged to seek before reaching a decision on the use of prenatal testing.
Note: The presence of a CPOX pathogenic variant detected by prenatal testing does not predict whether individuals will be symptomatic, or if they are, what the severity of the clinical manifestations will be. It is common for the offspring who inherit the CPOX pathogenic variant from a severely  individual to be completely asymptomatic.
Preimplantation genetic diagnosis (PGD) may be an option for some families with a genetic disorder for which the pathogenic variant is known.

Resources

GeneReviews staff has selected the following disease-specific and/or umbrella support organizations and/or registries for the benefit of individuals with this disorder and their families. GeneReviews is not responsible for the information provided by other organizations. For information on selection criteria, click here.
  • American Porphyria Foundation (APF)
    4900 Woodway
    Suite 780
    Houston TX 77056-1837
    Phone: 866-273-3635 (toll-free); 713-266-9617
    Fax: 713-840-9552
    Email: porphyrus@aol.com
  • National Library of Medicine Genetics Home Reference
  • European Porphyria Network
    Email: contact@porphyria.eu
  • NCBI Genes and Disease
  • Swedish Porphyria Patients' Association
    Karolinska Universitetssjukhuset
    Huddinge M 96
    Stockholm Stockholms Lan SE-141 86
    Sweden
    Phone: +46 8 711 56 09
    Email: porfyrisjukdomar@gmail.com
  • RDCRN Patient Contact Registry: Porphyrias Consortium

Molecular Genetics

Information in the Molecular Genetics and OMIM tables may differ from that elsewhere in the GeneReview: tables may contain more recent information. —ED.

Table A.

Hereditary Coproporphyria: Genes and Databases
Data are compiled from the following standard references: gene from HGNC; chromosome locus, locus name, critical region, complementation group from OMIM; protein from UniProt. For a description of databases (Locus Specific, HGMD) to which links are provided, click here.

Table B.

OMIM Entries for Hereditary Coproporphyria (View All in OMIM)
121300COPROPORPHYRIA, HEREDITARY; HCP
612732COPROPORPHYRINOGEN OXIDASE; CPOX
Gene structure. CPOX comprises seven exons; the reference sequence of the transcript is NM_000097.5. For a detailed summary of  and protein information, see Table AGene.
Pathogenic allelic variants. Pathogenic variants in all seven exons have been identified in persons with HCP (Human Gene Mutation Database, updated from ). They include missense and nonsense variants, small deletions, insertions, indels, splice variants, and large deletions.
Normal . Coproporphyringen-III oxidase (synonyms: coproporphyrinogen oxidase and coproporphyrinogen decarboxylase), the product of CPOX, performs an oxidative decarboxylation without a metal, reducing agents, or obligatory cofactors. The details of this unusual reaction remain to be elucidated. The crystal structure of human coproporphyringen-III oxidase points to a dimer as the catalytically active unit.
Abnormal . Some CPOX pathogenic variants likely alter enzyme activity by disrupting dimer formation [].
The 110-residue N-terminal segment is responsible for targeting the enzyme to mitochondria and is the site of its action on the substrate, coproporphyrinogen. Pathogenic variants in this region may affect  of the protein and, thus, reduce enzymatic function in tissues without changing activity in cell extracts.

References

Literature Cited

  1. Aggarwal N, Bagga R, Sawhney H, Suri V, Vasishta K. Pregnancy with acute intermittent porphyria: a case report and review of literature. J Obstet Gynaecol Res. 2002;28:160–2. [PubMed]
  2. Akagi R, Inoue R, Muranaka S, Tahara T, Taketani S, Anderson KE, Phillips JD, Sassa S. Dual gene defects involving delta-aminolaevulinate dehydratase and coproporphyrinogen oxidase in a porphyria patient. Br J Haematol. 2006;132:237–43. [PubMed]
  3. Anderson KE, Bloomer JR, Bonkovsky HL, Kushner JP, Pierach CA, Pimstone NR, Desnick RJ. Recommendations for the diagnosis and treatment of the acute porphyrias. Ann Intern Med. 2005;142:439–50.[PubMed]
  4. Anderson KE, Bonkovsky HL, Bloomer JR, Shedlofsky SI. Reconstitution of hematin for intravenous infusion.Ann Intern Med. 2006;144:537–8. [PubMed]
  5. Badminton MN, Deybach JC. Treatment of an acute attack of porphyria during pregnancy. Eur J Neurol.2006;13:668–9. [PubMed]
  6. Barbaro M, Kotajärvi M, Harper P, Floderus Y. Identification of an AluY-mediated deletion of exon 5 in the CPOX gene by MLPA analysis in patients with hereditary coproporphyria. Clin Genet. 2012;81:249–56.[PubMed]
  7. Billing BH. Twenty-five years of progress in bilirubin metabolism (1952-77). Gut. 1978;19:481–91. [PMC free article] [PubMed]
  8. Bissell DM. Treatment of acute hepatic porphyria with hematin. J Hepatol. 1988;6:1–7. [PubMed]
  9. Bissell DM, Lai JC, Meister RK, Blanc PD. Role of delta-aminolevulinic acid in the symptoms of acute porphyria. Am J Med. 2015;128:313–7. [PMC free article] [PubMed]
  10. Blake D, McManus J, Cronin V, Ratnaike S. Fecal coproporphyrin isomers in hereditary coproporphyria. Clin Chem. 1992;38:96–100. [PubMed]
  11. Bonkovsky HL, Siao P, Roig Z, Hedley-Whyte ET, Flotte TJ. Case records of the Massachusetts General Hospital. Case 20-2008. A 57-year-old woman with abdominal pain and weakness after gastric bypass surgery. N Engl J Med. 2008;358:2813–25. [PubMed]
  12. Brodie MJ, Thompson GG, Moore MR, Beattie AD, Goldberg A. Hereditary coproporphyria. Demonstration of the abnormalities in haem biosynthesis in peripheral blood. Q J Med. 1977;46:229–41. [PubMed]
  13. Dowman JK, Gunson BK, Bramhall S, Badminton MN, Newsome PN. Liver transplantation from donors with acute intermittent porphyria. Ann Intern Med. 2011;154:571–2. [PubMed]
  14. Farfaras A, Zagouri F, Zografos G, Kostopoulou A, Sergentanis TN, Antoniou S. Acute intermittent porphyria in pregnancy: a common misdiagnosis. Clin Exp Obstet Gynecol. 2010;37:256–60. [PubMed]
  15. Gibson PR, Grant J, Cronin V, Blake D, Ratnaike S. Effect of hepatobiliary disease, chronic hepatitis C and hepatitis B virus infections and interferon-alpha on porphyrin profiles in plasma, urine and faeces. J Gastroenterol Hepatol. 2000;15:192–201. [PubMed]
  16. Goetsch CA, Bissell DM. Instability of hematin used in the treatment of acute hepatic porphyria. N Engl J Med.1986;315:235–8. [PubMed]
  17. Hasanoglu A, Balwani M, Kasapkara CS, Ezgü FS, Okur I, Tümer L, Cakmak A, Nazarenko I, Yu C, Clavero S, Bishop DF, Desnick RJ. Harderoporphyria due to homozygosity for coproporphyrinogen oxidase missense mutation H327R. J Inherit Metab Dis. 2011;34:225–31. [PMC free article] [PubMed]
  18. Isenschmid M, König C, Fässli C, Haenel A, Hänggi W, Schneider H. Acute intermittent porphyria in pregnancy: glucose or hematin therapy? Schweiz Med Wochenschr. 1992;122:1741–5. [PubMed]
  19. Jara-Prado A, Yescas P, Sánchez FJ, Ríos C, Garnica R, Alonso E. Prevalence of acute intermittent porphyria in a Mexican psychiatric population. Arch Med Res. 2000;31:404–8. [PubMed]
  20. Kühnel A, Gross U, Doss MO. Hereditary coproporphyria in Germany: clinical-biochemical studies in 53 patients. Clin Biochem. 2000;33:465–73. [PubMed]
  21. Lamoril J, Puy H, Whatley SD, Martin C, Woolf JR, Da Silva V, Deybach JC, Elder GH. Characterization of mutations in the CPO gene in British patients demonstrates absence of genotype-phenotype correlation and identifies relationship between hereditary coproporphyria and harderoporphyria. Am J Hum Genet.2001;68:1130–8. [PMC free article] [PubMed]
  22. Lee DS, Flachsová E, Bodnárová M, Demeler B, Martásek P, Raman CS. Structural basis of hereditary coproporphyria. Proc Natl Acad Sci U S A. 2005;102:14232–7. [PMC free article] [PubMed]
  23. Ma E, Mar V, Varigos G, Nicoll A, Ross G. Haem arginate as effective maintenance therapy for hereditary coproporphyria. Australas J Dermatol. 2011;52:135–8. [PubMed]
  24. Rosipal R, Lamoril J, Puy H, Da Silva V, Gouya L, De Rooij FW, Te Velde K, Nordmann Y, Martàsek P, Deybach JC. Systematic analysis of coproporphyrinogen oxidase gene defects in hereditary coproporphyria and mutation update. Hum Mutat. 1999;13:44–53. [PubMed]
  25. Sadeh M, Blatt I, Martonovits G, Karni A, Goldhammer Y. Treatment of porphyric convulsions with magnesium sulfate. Epilepsia. 1991;32:712–5. [PubMed]
  26. Schmitt C, Gouya L, Malonova E, Lamoril J, Camadro JM, Flamme M, Rose C, Lyoumi S, Da Silva V, Boileau C, Grandchamp B, Beaumont C, Deybach JC, Puy H. Mutations in human CPO gene predict clinical expression of either hepatic hereditary coproporphyria or erythropoietic harderoporphyria. Hum Mol Genet. 2005;14:3089–98. [PubMed]
  27. Shenhav S, Gemer O, Sassoon E, Segal S. Acute intermittent porphyria precipitated by hyperemesis and metoclopramide treatment in pregnancy. Acta Obstet Gynecol Scand. 1997;76:484–5. [PubMed]
  28. Singal AK, Parker C, Bowden C, Thapar M, Liu L, McGuire BM. Liver transplantation in the management of porphyria. Hepatology. 2014;60:1082–9. [PMC free article] [PubMed]
  29. Soonawalla ZF, Orug T, Badminton MN, Elder GH, Rhodes JM, Bramhall SR, Elias E. Liver transplantation as a cure for acute intermittent porphyria. Lancet. 2004;363:705–6. [PubMed]
  30. Stein P, Badminton M, Barth J, Rees D, Stewart MF., British and Irish Porphyria Network. Best practice guidelines on clinical management of acute attacks of porphyria and their complications. Ann Clin Biochem.2013;50:217–23. [PubMed]
  31. van de Steeg E, Stránecký V, Hartmannová H, Nosková L, Hřebíček M, Wagenaar E, van Esch A, de Waart DR, Oude Elferink RP, Kenworthy KE, Sticová E, al-Edreesi M, Knisely AS, Kmoch S, Jirsa M, Schinkel AH. Complete OATP1B1 and OATP1B3 deficiency causes human Rotor syndrome by interrupting conjugated bilirubin reuptake into the liver. J Clin Invest. 2012;122:519–28. [PMC free article] [PubMed]
  32. van Tuyll van Serooskerken AM, de Rooij FW, Edixhoven A, Bladergroen RS, Baron JM, Joussen S, Merk HF, Steijlen PM, Poblete-Gutiérrez P, te Velde K, Wilson JH, Koole RH, van Geel M, Frank J. Digenic inheritance of mutations in the coproporphyrinogen oxidase and protoporphyrinogen oxidase genes in a unique type of porphyria. J Invest Dermatol. 2011;131:2249–54. [PubMed]
  33. Vercesi AE, Castilho RF, Meinicke AR, Valle VG, Hermes-Lima M, Bechara EJ. Oxidative damage of mitochondria induced by 5-aminolevulinic acid: role of Ca2+ and membrane protein thiols. Biochim Biophys Acta. 1994;1188:86–92. [PubMed]
  34. Whatley SD, Mason NG, Woolf JR, Newcombe RG, Elder GH, Badminton MN. Diagnostic strategies for autosomal dominant acute porphyrias: retrospective analysis of 467 unrelated patients referred for mutational analysis of the HMBS, CPOX, or PPOX gene. Clin Chem. 2009;55:1406–14. [PubMed]

Chapter Notes

Acknowledgments

The work has been carried out under the auspices of the Porphyria Rare Disease Clinical Research Consortium (KE Anderson, Galveston, TX; DM Bissell, San Francisco, CA; JR Bloomer, Birmingham AL; HL Bonkowsky, Charlotte, NC; RJ Desnick, New York, NY; and JD Phillips, Salt Lake City, UT). The Consortium receives essential support from the NIH/NIDDK (1 U54 DK083909) and the American Porphyria Foundation.

Author History

D Montgomery Bissell, MD (2012-present)
Theora Cimino, BS; University of California San Francisco (2012-2015)
Jennifer Lai, MD (2012-present)
Bruce Wang, MD (2012-present)

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