Megumi Mizawa, Teruhiko Makino, Hajime Nakano, Daisuke Sawamura, Tadamichi Shimizu
DOI: 10.2340/00015555-3184

Erythropoietic protoporphyria is caused by a partial deficiency of ferrochelatase, which is the last enzyme in the heme biosynthesis pathway. In a typical erythropoietic protoporphyria, photosensitivity initially appears, following the first exposure to the sun in early infancy or childhood. Erythropoietic protoporphyria has been reported worldwide, but there is a regional variation in its epidemiology. Approximately 20% of the Japanese patients were recognized to have symptoms of erythropoietic protoporphyria after 10 years of age. Physicians occasionally encounter Japanese patients with erythropoietic protoporphyria, mild symptoms and no FECH gene mutations. The homozygous IVS3-48C polymorphism may cause a mild phenotype of the erythropoietic protoporphyria via a slight increase in protoporphyrin. The frequency of the homozygous IVS3-48C polymorphism in the Japanese population is higher than that observed in European countries. Japanese type of erythropoietic protopor­phyria shows a characteristic phenotype of the late onset and mild symptoms compared to the Caucasian erythropoietic protoporphyria. This review describes the characteristics of erythropoietic protoporphyria in Japanese patients.

Erythropoietic protoporphyria (EPP) is a rare autosomal dominant disorder of heme biosynthesis, which results from a decrease in ferrochelatase activity, leading to an excess accumulation of protoporphyrin. EPP is characterized by painful photosensitivity, which begins in early childhood. The time of onset in Japanese patients may be later than in patients of other ethnicities. The homozygous IVS3-48C polymorphism may cause a mild phenotype of EPP via a slight increase in protoporphyrin. Japanese EPP shows a characteristic phenotype, such as the late onset and mild symptoms compared to Caucasian EPP.