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Author: Vanessa Ngan, Staff Writer, 2003. Updated by Hon A/Prof Amanda Oakley, August 2015.
Erythropoietic protoporphyria (EPP) is one of a group of genetic diseases called the porphyrias. EPP is due to an inherited deficiency of the enzyme ferrochelatase. Reduced activity of this enzyme causes a build-up of the chemical protoporphyrin in the skin; resulting in photosensitivity the skin is damaged by light. Abnormally high levels of protoporphyrin can rarely cause liver disease.
Prevalence of EPP in Europe varies from 1 in 55,000 to 1 in 150,000 of the population. It affects males and females equally, and people of all races may get EPP.
EPP is thought to be due to a compound loss-of-function mutation in the gene encoding ferrochelatase (FECH; 612386) found on chromosome 18q21. Typically, there is a mutation on one gene as well as a second, low-expression allele. Both males and females are equally affected. Rarely, there is a gain in function mutation in ALA synthase (ALAS)-2 (X-linked dominant inheritance). Thus, inheritance can be autosomal recessive or autosomal dominant with incomplete penetrance (96% of patients in the UK).
Myelodysplasia is a neoplastic proliferation of bone marrow cells and causes chromosomal instability. Acquired EPP has been described in an older woman with myelodysplasia and was found to be due to knock-out loss of chromosome 18.
First symptoms usually appear in infancy or early childhood and present as an uncomfortable or painful burning sensation of the skin after sun exposure. It occurs most often on the tops of the hands and feet, face and ears. In most cases visible changes are mild. The affected skin may become red and swollen and blistered. Later there are pitted scars and sometimes crusty thickened skin, particularly over the cheeks, nose and knuckles of the hands.
Mild EPP causes visible swelling and mild discomfort following exposure to the sun. It affects the face and the backs of the hands and feet.
People with EPP-induced liver disease often have mild changes in liver blood tests. About 10% develop more severe liver disease, presenting with malaise, pain under the ribs on the right, jaundice and increasing photosensitivity.
Gallstones are common in patients with EPP.
Diagnosis of EPP is often made during childhood.
The following monitoring tests are often performed from time to time.
Lifelong photosensitivity is the major problem for EPP uncomplicated by liver disease.
Trials of treatment for EPP have been difficult to assess. Effective treatment should reduce pain and increase time outdoors without pain.
Individual patients may experience benefit from oral anti-oxidants such as beta-carotene and N-acetyl cysteine. They should avoid iron supplementation (unless severely iron deficient), as iron can increase photosensitivity in EPP.
Another more serious condition, congenital erythropoietic porphyria, is now curable by stem cell transfusion, paving hope for the future, but there is not yet a cure available for EPP.
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