This form of hepatic Porphyria is most common in South Africans of Dutch ancestry. It is relatively uncommon elsewhere. It is an autosomal dominant disorder and may produce acute attacks (as in AIP) as well as chronic skin photosensitivity. The deficient enzyme is protoporphyrinogen oxidase. In acute attacks, urine PBG is increased as in AIP. Diagnosis of latent carriers is made by finding excess coproporphyrin in urine and both coproporphyrin and protoporphyrin in feces, or by DNA mutation analysis (see AIP). The most sensitive screening test for VP is probably a plasma porphyrin assay. In patients with skin manifestations, it is important to distinguish VP or HCP from PCT, because treatment by phlebotomy or low-dose chloroquine is ineffective in VP and HCP. Acute attacks are managed and may be prevented as in AIP.
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