Epidemiology of X-linked adrenoleukodystrophy in Japan

To clarify the epidemiology of X-linked adrenoleukodystrophy (ALD) in Japan, we performed a questionnaire survey. Two hundred eighty-six patients, including 154 from internal medicine, 100 from pediatrics, 21 from psychiatry, and 11 from other hospitals, were reported to have ALD between 1990 and 1999. The data on 154 patients revealed the phenotypic distribution to be as follows: childhood cerebral form (29.9%), adrenomyeloneuropathy (25.3%), adult cerebral form (21.4%), adolescent form (9.1%), olivo-ponto-cerebellar form (8.4%), presymptomatic form (4.5%), and symptomatic female patient (1.3%). The adult cerebral form and olivo-ponto-cerebellar form were more common in Japan than in North America and Europe. The incidence of X-linked ALD in Japan was estimated to be between 1 : 30,000 and 1 : 50,000 boys, similar to previous reports. About half of the patients with adrenomyeloneuropathy and the olivo-ponto-cerebellar phenotype developed cerebral involvement with a mean interval of 8.2 and 2.2 years after ALD onset, respectively. The family histories revealed that brothers and first cousins tended to show similar phenotypes, whereas nephews tended to develop symptoms earlier than uncles. These data will help in understanding the natural history of X-linked ALD.