Porphyria

Any of a group of uncommon and usually inherited disorders caused by the accumulation of substances called porphyrins. Sufferers often have a rash or blistering brought on by sunlight, and certain drugs may cause abdominal pain and nervous system disturbances. Porphyrins are formed in the body during the manufacture of haem (a component of haemoglobin). A block in this manufacture causes a build-up of porphyrins. Such blocks are the result of various enzyme deficiencies, which are genetic disorders. Porphyria may also be due to poisoning. There are 6 types of porphyria. Acute intermittent porphyria usually appears in early adulthood, causing abdominal pain, and often limb cramps, muscle weakness, and psychiatric disturbances. The patient’s urine turns red when left to stand. Barbiturate drugs, phenytoin, oral contraceptives, and tetracyclines precipitate attacks. Variegate porphyria has similar effects but also causes blistering of sun-exposed skin. Hereditary coproporphyria also has similar effects and may cause additional skin symptoms. Protoporphyria usually causes skin symptoms after exposure to sunlight, as does porphyria cutanea tarda. In this type, wounds are slow to heal, and urine is sometimes pink or brown. Many cases are precipitated by liver disease. The rarest and most serious form, congenital erythropoietic porphyria, causes red discoloration of urine and the teeth, excessive hair growth, severe skin blistering and ulceration, and haemolytic anaemia. Death may occur in childhood. Diagnosis is made from abnormal levels of porphyrins in the urine and faeces. Treatment is difficult. Avoiding sunlight and/or precipitating drugs is the most important measure. Acute intermittent porphyria, variegate porphyria, and hereditary coproporphyria may be helped by administration of glucose or haematin. Cases of porphyria cutanea tarda may be helped by venesection.