Human T-lymphotropic virus type I: A retrovirus causing chronic myeloneuropathies in tropical and temperate climates.

Human T-cell lymphotropic virus type I (HTLV-I), the first human retrovirus to be isolated, is the cause of endemic tropical spastic paraparesis (TSP). Originally, this chronic neurological disorder was described as a disease seen among blacks of low socioeconomic status living in tropical countries, and thus for many decades TSP remained a little known curiosity outside the endemic regions. The link between HTLV-I infection and TSP was made fortuitously, when antibodies to HTLV-I were found in serum and cerebrospinal fluid of TSP patients in Jamaica, Colombia, and Martinique. Soon thereafter a similar disorder, designated HTLV-I associated myelopathy (HAM), was reported from southern Japan. This broadened the geographic and ethnic boundaries of this chronic myelopathy and the disease has now been reported in multiple ethnic groups from more than 40 countries, in both tropical and temperate regions. The name TSP/HAM is now used to include all patients (regardless of race or country of origin) who have HTLV-I-positive endemic TSP or HAM.