Uroporphyrinogen III synthase converts hydroxymethylbilane to uroporphyrinogen III. A defect in this enzyme results in congenital erythropoietic porphyria (CEP).


Synonym: Gunther disease


Inheritance: autosomal recessive


Genetic locus: 10q26


Clinical features:

(1) bullae and skin fragility

(2) no neurovisceral signs and symptoms

(3) occasionally a hemolytic anemia

(4) occasionally erythrodontia


Laboratory findings:

(1) porphobilinogen and aminolevulinic acid are not increased in the urine

(2) porphyrins are increased in the urine with uroporphyringen I greater than coproporphyrinogen I

(3) coproporphyrinogen I is increased in the feces

(4) erythrocytes contain zinc protoporphyrin, coproporphyrinogen and uroporphyrinogen

(5) no accumulation of coproporphyrinogen III or uroporphyrinogen III or protoporphyrinogen IX


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