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Variegate Porphyria

Variegate porphyria is a type of porphyria that is associated with the symptoms of the neurovisceral crises similar to the patient with AIP but is also associated with a classic photosensitive skin disorder. The defective gene is located on chromosome number 1and is inherited in an autosomal dominant fashion. The rate limiting enzyme is protoporphyrinogen oxidase (PPO) which controls one of the final stages of heme synthesis, the oxidation of protoporphyrinogen-IX to protoporphyrin. In patients with this disease, the activity of PPO is reduced by at least 50%. It is relatively common in the white Afrikan population of South Africa. The disease rarely appears before puberty, is most common in the young adult but may suddenly occur at any age including the elderly.

The neurovisceral crises give symptoms similar to those of patients suffering from AIP, while the photodermatitis shows the typical findings of the standard nonspecific form of skin sensitivity to solar radiation. These changes include skin fragility, erosions and blisters during the acute attack, and abnormal pigmentation, skin thickening and hirsuitism due to chronic exposure. The precipitating factors are also similar to those of AIP although some experts feel that the acute attacks of VP are not related to menstrual cycles. There is very little clinical evidence to show that VP is a cause of long term psychiatric disease. With an acute attack, the urine may turn red and there is always an increase in the excretion of PBG and ALA in the urine. There are increased porphyrins in the urine with coproporphyrins excreted in excess of uroporphyrins. The severity of the attack may be related to the concentration of these porphyrins. Increased levels of both protoporphyrin and coproporphyrin are also found in the feces. These abnormal findings may return to normal when the disease is quiescent or in remission. Many people who are asymptomatic carriers of the abnormal gene will consistently have negative laboratory tests. The enzyme PPO is not present in red cells and is technically very difficult to measure.

The treatment of the neurovisceral attacks is similar to that used in AIP, including the administration of hematin. The standard dermatological therapies for photodermatitis are usually ineffective and patients should be advised to avoid sun exposure and to use sunscreens containing zinc oxide or titanium oxide. If both parents carry the abnormal gene so that the patient is homozygous, the disease will present in early childhood and be rather severe. However the outlook for the heterozygous individual is good.