HTLV-I-associated myelopathy (HAM) in Tokushima Prefecture--geographical and clinical studies in an area between endemic and non-endemic areas of HTLV-I infection.

The geographic distribution and clinical features of patients with HTLV-I-associated myelopathy (HAM) in Tokushima prefecture were investigated. Nine patients were found prior to December 1990. The minimal prevalence was estimated as 1.1 per 100,000 in the general population, and 1 per 1,309 in HTLV-I-seropositive persons. Seven patients were found in the southern district facing the Pacific Ocean, but only 1 patient each was found in the northern and western districts. The age at disease onset ranged from 15 to 53 yr (average 33 yr). The ratio of male to female patients was 1:8. Adult T cell leukemia was associated with HAM in 1 patient, and Hashimoto's disease in 2 patients. These cases have not been reported previously. The route of transmission of HTLV-I was concluded to be vertical in 4 patients and horizontal in 4 patients, but was uncertain in 1 patient. No evidence of transmission by blood transfusion was found in these patients.