HTLV-I-associated leukemia: a model for chronic retroviral diseases.

Human T-lymphotropic virus type I (HTLV-I) has been associated with adult T-cell leukemia/lymphoma (ATL), a malignancy of mature CD4-positive lymphocytes, and with tropical spastic paraparesis (TSP), a demyelinating neurological syndrome. This article describes the clinical and pathological features of ATL and reviews the epidemiology of this disease and of its putative etiological agent, HTLV-I. From what is known about the molecular biology and epidemiology of HTLV-I, hypotheses on the etiology of TSP are proposed, and strategies for studying the neurological syndrome are suggested.