Wednesday, November 30, 2016
Let's get Down on VP
What is Variegate Porphyria?
VP is caused by a mutation in the enzyme protoporphyrinogen oxidase (PPOX), which is part of the pathway that produces porphyrins and heme. Acute attacks are similar to those in AIP and HCP but are unusual. A more common sign of the disease is blistering skin lesions, which are chronic in many people with VP.
Acute attacks almost always start with severe pain in the abdomen but sometimes in the chest, back, or thighs, and are often accompanied by nausea, vomiting, and constipation. Heart rate and blood pressure are commonly increased. These symptoms and signs are all due to the effects of the disease on the nervous system. Confusion, convulsions, and muscular weakness, due to impairment of the nerves controlling the muscles, may lead to paralysis. An acute attack usually lasts for days or weeks. Recovery from severe paralysis is generally slow.
Who gets Variegate Porphyria?
VP is especially common in South Africa in individuals of Dutch ancestry, where it has been estimated that 3 in 1,000 of the white population are affected. It is much less prevalent in other countries. Like AIP and HCP, it is an autosomal dominant disorder, meaning that a mutation is present in only one of the pair of PPOX genes.
What causes Variegate Porphyria?
As in HCP, acute attacks of VP are unusual except in the presence of environmental activating factors, such as drugs, hormones, and dietary changes.
How is Variegate Porphyria Diagnosed?
Urine ALA and PBG are increased during attacks, but as in HCP, these may increase less and decrease more rapidly than in AIP. Plasma porphyrins are frequently increased in VP, in contrast to AIP and HCP, and the plasma of VP patients displays a distinctive fluorescence peak, which is diagnostic. Fecal porphyrins are also elevated and are predominantly coproporphyrin III and protoporphyrin.
What are treatments for Variegate Porphyria?
Management and prevention are the same as in AIP and HCP. Blistering skin lesions are much more common than in HCP and are not readily treated. The only effective preventive measure is use of protective clothing.
What is the long-term outlook after an attack of Vairegate Porphyria?
The prognosis is usually good if the disease is recognized and treated promptly, before nerve damage develops. Although symptoms usually resolve after an attack, recovery of neuromuscular function (in a severe case) may require several months. Mental symptoms may occur during attacks but are not chronic. Premenstrual attacks often resolve quickly with the onset of menses.
Can attacks be prevented?
Yes, particularly with regard to drugs and diet. Genetic VP carriers should become informed on medications to avoid (see information on AIP and HCP) and should be prepared to point their healthcare providers to on-line drug lists that are regularly updated. The American Porphyria Foundation offers a mobile phone app that pulls up this information on line (http://porphyriadrugs.com/). A Medic Alert bracelet is useful for a situation in which the patient is incapacitated. Very frequent premenstrual attacks can be prevented by a gonadotropin-releasing hormone (GnRH) analogue (Lupron, Zoladex, others) administered with expert guidance. In selected cases, frequent noncyclic attacks can be prevented by once- or twice-weekly infusions of hemin.
Individuals who are prone to attacks should consume a normal balanced diet. Despite on-line discussion, there is no evidence that pushing carbohydrate prevents attacks, and it has the side effect of weight gain, which is undesirable for most people. Fasting, fad diets (for example, high protein) and gastric reduction surgery should be avoided. If weight loss is desired, it is advisable to consult a physician and a dietitian about an individualized diet with modest caloric restriction (ca. 10%), which will produce gradual weight loss without increasing the risk of an attack of porphyria. Exercise is safe in porphyria, and recommended.
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