porphyria cutanea tarda

porphyria /por·phy·ria/ (por-fēr´e-ah) any of a group of disturbances of porphyrin metabolism characterized by increase in formation and excretion of porphyrins or their precursors.

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acute intermittent porphyria  (AIP) hereditary hepatic porphyria due to a defect of pyrrole metabolism, with recurrent attacks of abdominal pain, gastrointestinal and neurologic disturbances, and excessive amounts of δ-aminolevulinic acid and porphobilinogen in the urine.

congenital erythropoietic porphyria  (CEP) a form of erythropoietic porphyria, with cutaneous photosensitivity leading to mutilating lesions, hemolytic anemia, splenomegaly, excessive urinary excretion of uroporphyrin and coproporphyrin, and invariably erythrodontia and hypertrichosis.

porphyria cuta´nea tar´da  (PCT) a form characterized by cutaneous sensitivity that causes scarring bullae, hyperpigmentation, facial hypertrichosis, and sometimes sclerodermatous thickenings and alopecia; it is associated with reduced activity of an enzyme of heme synthesis.

erythropoietic porphyria  that in which excessive formation of porphyrin or its precursors occurs in bone marrow normoblasts, including congenital erythropoietic porphyria and erythropoietic protoporphyria.

hepatic porphyria  that in which the excess formation of porphyrin or its precursors occurs in the liver.

hepatoerythropoietic porphyria  (HEP) a severe form of porphyria cutanea tarda believed to result from a lack of activity of the enzyme catalyzing the conversion of uroporphyrinogen to coproporphyrinogen in the biosynthesis of heme.

variegate porphyria  (VP) a hereditary hepatic porphyria, with chronic skin manifestations, chiefly extreme mechanical fragility of the skin, mainly of areas exposed to sunlight, episodes of abdominal pain, neuropathy, and typically an excess of coproporphyrin and protoporphyrin in bile and feces.

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porphyria cu·ta·ne·a tar·da (ky-tn- târd)

n.

Abbr. PCT Porphyria characterized by liver dysfunction and photosensitive cutaneous lesions, with hyperpigmentation and scleroderma-like changes in skin, neurologic manifestations, and porphyrinuria. Also called symptomatic porphyria.

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Porphyria cutanea tarda

An inherited disease that results in the overproduction of porphyrins.

Mentioned in: Hyperpigmentation

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porphyria cutanea tarda (PCT),

the most common form of porphyria, characterized by cutaneous photosensitivity that causes scarring bullae, hyperpigmentation, facial hypertrichosis, and sometimes sclerodermatous thickenings and alopecia. It is frequently associated with alcohol abuse, liver disease, or hepatic siderosis. Urinary levels of uroporphyrin and coproporphyrin are increased, and activity of a specific enzyme involved in heme biosynthesis is decreased. The cause is debated, but two types are generally recognized: an autosomal-dominant (or familial) form in which activity of the affected enzyme is reduced to half normal in liver, erythrocytes, and fibroblasts, and a sporadic (but probably also familial) form in which the reduction is confined to the liver. Both types are believed to be heterozygous, with clinical expression occurring in adulthood, precipitated by disease or environmental factors. A more severe homozygous form begins in childhood and is called hepatoerythropoietic porphyria. See also porphyria.

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porphyria [por-fēr´e-ah]

a genetic disorder characterized by a disturbance in porphyrin metabolism with resultant increase in the formation and excretion of porphyrins (uroporphyrin and coproporphyrin) or their precursors; called also hematoporphyria. Porphyrins, in combination with iron, form hemes, which in turn combine with specific proteins to form hemoproteins. hemoglobin is a hemoprotein, as are many other substances essential to normal functioning of the cells and tissues of the body.

Two general types are known: the erythropoietic porphyrias, which are concerned with the formation of erythrocytes in the bone marrow; and the hepatic porphyrias, which are responsible for liver dysfunction. Manifestations of porphyria include gastrointestinal, neurologic, and psychologic symptoms, cutaneous photosensitivity, pigmentation of the face (and later of the bones), and anemia with enlargement of the spleen. Large amounts of porphyrins are excreted in the urine and feces.

Treatment of this condition has been primarily symptomatic and varies in its effectiveness. Emphasis is on prevention of attacks by avoiding fasting and drugs that precipitate the symptoms. Photosensitivity may be controlled by avoiding exposure to light. Removal of the spleen is useful in some cases of the erythropoietic type of porphyria. Drug therapy includes the use of phenothiazines, chlorpromazine and promazine in particular. These drugs allay pain and nervousness and apparently allow a period of remission from symptoms. Meperidine hydrochloride (Demerol) may be given for pain and hydroxypheme (Hemetin) is given intravenously to compensate for genetic impairment of heme synthesis.

Patients with porphyria must not be given barbiturates, sulfonamides, alcohol, or chloroquine as these chemicals may precipitate or intensify attacks. It is recommended that persons with this disease carry with them at all times identification saying that they have porphyria so that in an emergency they will not be given medication that could precipitate an attack or even death.

acute intermittent porphyria (AIP) a hereditary, autosomal dominant, form of hepatic porphyria manifested by recurrent attacks of abdominal pain, gastrointestinal dysfunction, and neurologic disturbances, and by excessive amounts of δ-aminolevulinic acid and porphobilinogen in the urine; it is due to an abnormality of pyrrole metabolism. Called also intermittent acute porphyria.

congenital erythropoietic porphyria (CEP) a form of erythropoietic porphyria, with cutaneous photosensitivity leading to mutilating lesions, hemolytic anemia, splenomegaly, excessive urinary excretion of uroporphyrin and coproporphyrin, and invariably erythrodontia and hypertrichosis. Called also Günther disease.

porphyria cuta´nea tar´da (PCT) the most common form of porphyria, characterized by cutaneous photosensitivity that causes scarring bullae, discoloration, growth of facial hair, and sometimes sclerodermatous thickenings and alopecia; it is frequently associated with alcohol abuse, liver disease, or hepatic siderosis. Urinary levels of uroporphyrin and coproporphyrin are increased. There are two main types: an autosomal dominant (or familial ) form in which activity of the affected enzyme is reduced to half normal in liver, erythrocytes, and fibroblasts; and a sporadic (but probably also familial) form in which the reduction is confined to the liver. Both types are believed to be heterozygous and clinical expression occurs in adulthood, precipitated by disease or environmental factors. A more severe homozygous form begins in childhood and is called hepatoerythropoietic porphyria.

erythropoietic porphyria porphyria in which excessive formation of porphyrin or its precursors occurs in bone marrow erythroblasts; the group includes congenital erythropoietic porphyria and erythropoietic protoporphyria.

hepatic porphyria porphyria in which the excess formation of porphyrin or its precursors is found in the liver; it includes acute intermittent porphyria, variegate porphyria, and hereditary coproporphyria.

hepatoerythropoietic porphyria (HEP) a severe homozygous form of porphyria cutanea tarda believed to result from an autosomal dominant defect in the same enzyme as is affected in porphyria cutanea tarda; it is clinically identical to that disease but onset is in early childhood and enzyme activity in liver, erythrocytes, and fibroblasts is virtually absent.

intermittent acute porphyria acute intermittent porphyria.

porphyria variega´ta (variegate porphyria (VP)) a hereditary, autosomal dominant, type of hepatic porphyria characterized by chronic cutaneous manifestations, notably extreme mechanical fragility of the skin, particularly areas exposed to the sunlight, and by episodes of abdominal pain and neuropathy. There is typically an excess of coproporphyrin and protoporphyrin in the bile and feces.

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porphyria cutanea tarda

Metabolic disease An AD condition caused by uroporphyrinogen decarboxylase deficiency Clinical Liver dysfunction, photosensitivity, hyperpigmentation, scleroderma-like skin changes Lab ↑ Uroporphyrin in urine