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-exposedskin. 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.
n. one of a group of rare disorders due to *inborn errors of metabolism in which there are deficiencies in the enzymes involved in the biosynthesis of haem. The accumulation of the enzyme’s substrate gives rise to symptoms of the disorder. The defect may be primarily in the liver (hepatic porphyria) or in the bone marrow (erythropoietic porphyria) or both. The prominent features include the excretion of *porphyrins and their derivatives in the urine, which may change colour on standing (see porphobilinogen); sensitivity of the skin to sunlight causing chronic inflammation or blistering; inflammation of the nerves (neuritis); mental disturbances; and attacks of abdominal pain. The commonest porphyria is porphyria cutanea tarda, which affects up to 1 in 5000 people in some countries. It is a hereditary or acquired hepatic porphyria in which light-exposed areas of the skin become blistered and fragile. Acute intermittent porphyria is a hereditary hepatic porphyria characterized by recurrent attacks of acute abdominal pain, severe constipation, and psychotic behaviour. Factors triggering attacks include alcohol and many drugs.
A group of rare inherited ENZYME diseases in which disorders of the metabolic pathways leading to the synthesis of HAEM cause excessive production of haem precursors called PORPHYRINS by the bone marrow or liver. The excess porphyrins in the blood mainly affect the skin, causing PHOTOSENSITIVITY, or the central nervous system, causing various neuro-psychiatric disorders. Excess porphyrins can be detected in blood, urine and faeces. Usually porphyrias are genetically determined, but one form is due to alcoholic liver disease. The commonest form, porphyria cutanea tarda, affects up to 1 in 5,000 people in some countries. The British king, George III, suffered from porphyria, a disorder unrecognised in the 18th century.... porphyrias
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