The familial form of porphyria cutanea tarda — is inherited as an autosomal dominant trait with males and females affected in multiple generations. The enzyme UROD is reduced in all tissues.
The sporadic form of porphyria cutanea tarda — is more common. The enzyme UROD is only reduced in the liver. It appears sporadically in people with liver disease, as from alcoholism, and from exposure to agents such as estrogens.
Iron overload is frequently present in porphyria cutanea tarda and may be associated with varying degrees of damage of the liver.
A severe form of porphyria cutanea tarda, hepatoerythropoietic porphyria (HEP), has its onset in infancy with the accumulation of protoporphyrin in the red blood cells. The level of the enzyme UROD is very low in red cells.
The UROD gene has been mapped to 1p34. Mutations have been identified in the UROD gene, including DNA base substitutions and deletions. These mutations result in reduced activity of the enzyme. Some mutation result in porphyria cutanea tarda and others in the recessively inherited HEP. HEP is the homozygous form of familial porphyria cutanea tarda.
Treatment is directed first at reducing iron overload by regular phlebotomy (removal of blood). Then treatment with the drug hydroxychloroquine usually induces a sustained remission.
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