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Author: Dr Chin-Yun Lin, Dermatology Registrar, Auckland Hospital, New Zealand, 2010.
Congenital erythropoietic porphyria (CEP) is very rare metabolic disorder affecting the synthesis of haem, the iron-containing pigment that binds oxygen onto red blood cells.
It was initially described by Hans Gunther so is also known as Gunther disease.
CEP is an inherited disorder in which there is a mutation in a gene on chromosome 10 that encodes uroporphyrinogen III synthase. CEP is autosomal recessive, which means an abnormal gene has been inherited from both parents. Carriers of a single abnormal gene do not usually exhibit any signs or symptoms of the disorder.
Homozygous mutation leads to deficiency of uroporphyrinogen III synthase and uroporphyrinogen cosynthetase.
Normally, activity of the enzyme uroporphyrinogen III synthase leads to the production of isomer III porphyrinogen, needed to form haem.
When uroporphyrinogen III synthase is deficient, less isomer III and more isomer I porphyrinogen is produced. Isomer I porphyrinogens are spontaneously oxidized to isomer 1 porphyrins, which accumulate in the skin and other tissues. They have a reddish hue.
Porphyrins are photosensitisers, ie, they injure the tissues when exposed to light.
Clinical manifestations of CEP may be present from birth and can range from mild to severe.
The diagnosis of CEP is confirmed by finding high levels of porphyrins in urine, faeces and circulating red blood cells. Findings are:
CEP persists lifelong.
It is essential to protect the skin from all forms of daylight to reduce pain, burning, swelling and itching. Indoors, incandescent lamps are more suitable than fluorescent lamps and protective films can be placed on the windows to reduce the light that provokes porphyria.
Some patients have been helped by:
Bone marrow transplant has been successful in a few cases, although long term results are not yet available. At present, this treatment is experimental.
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