Incidence of adult T‐cell leukemia‐lymphoma and its familial clustering

The yearly incidence of ATLL in the Uwajima district is 6.6 patients per 100,000 inhabitants aged over 40. The yearly morbidity rate from ATLL of persons in this district who are positive for HTLV‐antibody and older than 40 is I patient per 1,631. Familial occurrence was observed in 9/38 families available for pedigree analyses. Even in the endemic area, the existence of positive HTLV antibody is remarkably high in ATLL families, suggesting that HTLV has been transmitted from generation to generation mainly within these particular families.