Porphyria Cutanea Tarda and Hepatoerythropoietic Porphyria
The most common of the porphyrias it can occur either as a familial disease, the heterozygous form of
the enzyme deficiency, or acquired through exposure to hexachlorobenzene and related chemical compounds.
The disorder is most common in men and usually appears after age 35.
Precipitating factors are increased ingestion of iron or alcohol and
estrogen use (particularly when combined with alcohol).
This pophyria has no neurological manifestations, but presents after minor
trauma to sun exposed skin causes vesicles or bullae to develop. The vesicles or bullae
are followed by erosions and scaring. Acute photosensitivity reactions are not common. In time
milia, areas of pigmentation and de-pigmentation, hirsutism, sclerodermoid changes occur. Patients with
untreated disease for a significant period of time may develop cirrhosis and hepatocellular carcinoma.
Laboratory Findings. Serum iron is often increased and liver biopsy usually shows hepatocellular
damage with fatty infiltration and hemosiderosis. Uroporphyrin to a greater extent than coproporphyrin are
both increased in the urine. In variegate porphyria the opposite is generally seen where coproporphyrin is
increased to a greater extent than uropophyrin. Other urine findings include a minimally increased
ALA and a normal PBG level. To distinguishing variegate porphyria from porphyria cutanea tarda the fecal
test is useful since a high fecal protoporphyrin is noted in variegate porphyria and increased
isocoproporphyrins, tetracarboxyl porphyrins, are excreted in porphyria cutanea tarda.
A deficiency of uroporphyrinogen decarboxylase activity is the basic defect and measurement of erythrocyte
uroporphyrinogen decarboxylase activity is useful in to diagnose the familial form of the disease. In the familial form the
reduce enzyme activity will be found in all tissues, but in exposure cases it is appears to be restricted to the liver.
Treatment. Use of repeated phlebotomy to deplete body iron causes a decrease of urinary porphyrin excretion
and improvement in the patient. Removal of 5-10 liters is usually required to develop clinical remission. The
therapy is monitored through following the level of urinary uroporphyrin excretion. If the patient is unable
to tolerate phlebotomy, then low dose chloroquine (125 - 250 mg three times a week) may be used in treatment.
This form of porphyria is quite rare and has been described in only about 20 patients. It is the homozygous form of uroporphyrinogen
decarboxylase deficiency (activity is 5-10% of normal). Parents of these children have an approximately 50% decrease in activity.
Generally the
skin manifestations of the disease are seen in the first year of life and resemble porphyria cutanea tarda. Eventually the patients
are severely affected with hirsutism, scarring, sclerodermoid changes, and acrosclerosis. As the child grows older
the skin lesions improve somewhat, but the hepatic involvement may become worse from a nonspecific hepatitis or inflammation
to possible cirrhosis.
A characteristic red fluorescence, nonspecific hepatitis or portal inflammation is seen on liver biopsy. A slight to modest increase in
serum transaminase and gamma transpeptidase levels may be noted. Hematopoietic findings in adults include a mild normochromic anemia and
a bone marrow demonstrating fluorescent normoblasts. The abnormalities in porphyrin metabolism are identical to porphyria
cutanea tarda with the addition of a increased level of zinc protoporphyrin level in erythrocytes.
Released: 2/8/95 ,
Last Reviewed: 2/8/95,
UT DPALM MEDIC, copyright 1995.