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Chronic hepatic porphyria
Chronic hepatic porphyrias represent a sub-group of porphyrias (see this term). They are characterized by bullous photodermatitis caused by a deficiency of uroporphyrinogen decarboxylase (URO-D; the fifth enzyme in the heme biosynthesis pathway). Chronic hepatic porphyria encompasses two diseases: porphyria cutanea tarda and hepatoerythropoietic porphyria (extremely rare) (see these terms).
ORPHA:95161Classification level: Group of disorders
- Synonym(s): -
- Prevalence: 1-9 / 100 000
- Inheritance: Autosomal dominant
- Age of onset: All ages
- ICD-10: E80.2
- OMIM: -
- UMLS: -
- MeSH: -
- GARD: -
- MedDRA: -
The prevalence of porphyria cutanea tarda is estimated at 1/25,000 in western Europe.
The disease can manifest in adulthood (porphyria cutanea tarda) or in childhood (hepatoerythropoietic porphyria). Patients present with cutaneous lesions (fragility, bullae, scars) on the surface of skin exposed to the sun (hands, face) and, unlike in cases of acute hepatic porphyrias (see this term), don't present with acute neuro-visceral attacks.
Chronic hepatic porphyria is caused by a deficiency in URO-D that leads to an accumulation of porphyrins in the liver. The enzyme deficiency is caused by heterogeneous mutations, in the case of porphyria cutanea tarda, of the URO-D gene coding for URO-D. Hepatoerythropoietic porphyria corresponds to homozygous and composite heterozygous cases of porphyria cutanea tarda. The acquired forms of the diseases may be triggered by risk factors (alcohol, hepatitis C, estrogen, iron overload).
Diagnosis is based on the measurement of concentrations of porphyrins in urine, stools and blood. The evidence of a deficiency of URO-D in red blood cells and the identification of a causal mutation of the URO-D gene allow a confirmed diagnosis.
Differential diagnoses include hereditary coproporphyria and variegate porphyria (see these terms).
For both diseases, transmission is autosomal dominant and penetrance is weak. Genetic counseling should be offered to patients to identify individuals susceptible to developing or transmitting the disease.
Management and treatment
Management includes protecting the skin from light. Phlebotomy and/or takin`g small doses of chloroquine results in complete remission, although a relapse is always possible. Treatment of concomitant hepatitis C is essential for remission to occur.
Porphyria cutanea tarda is not life-threatening and the prognosis is favorable. The prognosis of hepatoerythropoietic porphyria is less favorable.