Clustering and clinical diversity of adult T-cell leukemia/lymphoma associated with HTLV-I in a remote black population of French Guiana.

An epidemiological study was performed in French Guiana (population 115,000) to determine the prevalence and incidence of adult T-cell leukemia/lymphoma (ATL) associated with human T-cell leukemia/lymphoma virus type I (HTLV-I). From January 1990 to December 1993, all suspected cases of ATL were enrolled in this study, and their clinical, epidemiological and immunovirological features were analyzed. Out of the 19 suspected cases, 18 were considered as ATL associated with HTLV-I (8 acute forms, 8 lymphoma types and 2 smoldering cases). Before this study, only 2 ATL cases had been reported in French Guiana over a 10-year period. This demonstrates that the number of ATL cases is greatly under-estimated in most tropical HTLV-I endemic areas unless a specific disease search is performed. The mean age of the patients was 41 years. While HTLV-I antibodies were present in all cases, molecular studies demonstrated a clonal integration of HTLV-I in the tumoral cells in 7 cases out of the 9 tested. Fifteen patients died within a year of diagnosis. The crude incidence rate of ATL in French Guiana is around 3.5/100,000/year, a situation similar to that found in the Caribbean and in HTLV-I-endemic regions of Japan. However it reaches around 30/100,000/year (highest incidence ever described) in a small remote ethnic group of African origin (around 6200 inhabitants). Possible causes of ATL clustering in this ethnic group are presented.