Porphyrins Health Dictionary

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Porphyrins: From 1 Different Sources

Complex organic compounds which are sensitive to light and form the basis of respiratory pigments – for example, haemoglobin and myoglobin. Porphyrins are crucial to many metabolic oxidation/reduction reactions in animals, plants, and micro-organisms.
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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-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.... porphyria

Haem

An iron-containing porphyrin (see PORPHYRINS) compound that combines with the protein GLOBULIN to make HAEMOGLOBIN, a constituent of erythrocytes (red blood cells).... haem

Porphyrias

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

Porphin

n. a complex nitrogen-containing ring structure and parent compound of the *porphyrins.... porphin

Porphyrin

n. one of a number of pigments derived from *porphin, which are widely distributed in living things. All porphyrins form chelates with iron, magnesium, zinc, nickel, copper, and cobalt. These chelates are constituents of *haemoglobin, *myoglobin, the *cytochromes, and chlorophyll, and are thus important in many oxidation/reduction reactions in all living organisms. See also protoporphyrin IX.... porphyrin

Porphyrinuria

n. the presence in the urine of breakdown products of the red blood pigment haemoglobin (porphyrins), sometimes causing discoloration. See porphyria; porphobilinogen.... porphyrinuria

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