Porphyrias in Japan: compilation of all cases reported through 2002

The first case of porphyria on record in Japan was a patient with congenital erythropoietic porphyria (CEP) reported by Sato and Takahashi in 1920. Since then until the end of December 2002, 827 cases of porphyrias have been diagnosed from characteristic clinical and/or laboratory findings (463 males, 358 females, and 6 of unknown sex). Essentially all inherited porphyrias have been found in Japan, with the incidences and clinical symptoms generally being similar to those reported for other countries. The male-female ratio was approximately 1:1 for CEP, whereas it was higher for erythropoietic protoporphyria. In contrast, preponderances of female patients exist with acute hepatic porphyrias, such as acute intermittent porphyria (AIP), variegate porphyria (VP), and hereditary coproporphyria (HCP), and with undefined acute porphyria. Although porphyria cutanea tarda (PCT) is believed to be increasing recently in women in other countries because of smoking and the use of contraceptives, it is still by far more prominent in males in Japan than in females. The recent increasing contribution of hepatitis C virus infection to PCT in Japan has also been recognized. but there have been no PCT cases in Japan with HFE gene mutations. Familial occurrence and consanguinity were high for CEP, as expected; however, significant consanguinity was also noted in families where CEP, AIP, HCP, VP, or PCT occurred as a single isolated case without a family history of disease. This survey also revealed that as many as 71% of acute hepatic porphyria cases were initially diagnosed as nonporphyria and later revised or corrected to porphyria, indicating the difficulty of diagnosing porphyria in the absence of specific laboratory testing for porphyrins and their precursors in urine, stool, plasma, and erythrocyte samples.