The clinical syndrome earlier designated as paraparesia espástica del Pacífico is an isolated form of tropical spastic paraparesis (TSP) that was reported in 1981 in the southern Pacific lowlands of Columbia in and near Tumaco. The clinical features are similar to those of TSP reported in Jamaica, Martinique, the Seychelles, and the Ivory Coast of Africa and resemble also those clinical features of the human T-lymphotropic virus type I (HTLV-I)-associated myelopathy described in southern Japan. Since HTLV-I infection is closely associated with TSP, we conducted a case-control study to evaluate the role of HTLV-I-associated risk factors among patients from the endemic focus in Tumaco, Colombia, and the seroprevalence rates of this virus in other geographical areas of the Pacific Colombian lowlands with and without TSP. From our seroprevalence study of antibodies to HTLV-I among TSP index patients, matched controls, household contacts (first- and second-degree relatives), and healthy controls from these areas, we found a strong association between HTLV-I and TSP. Also, there is a high seroprevalence of HTLV-I among sexual partners of patients and to a lesser extent among their offspring and other relatives some of whom had an early mean acquisition of antibodies to HTLV-I. Heterosexual promiscuity and other close interpersonal contact may play an important role in the transmission of TSP in the Pacific lowlands of Colombia.

A high-incidence focus of tropical spastic paraparesis (TSP) occurs on the South Pacific coast of Colombia. Of 55 patients studied, 52 (94.5%) had IgG antibodies to the human T-cell lymphotropic virus type I (HTLV-I) in serum and/or cerebrospinal fluid. Control groups did not show similar high positivity. Our results suggest that HTLV-I or other antigenically related retroviruses may be the cause of TSP in Colombia. Similar clinical, laboratory, and epidemiological findings have been reported in widely remote geographical regions of the world, with very similar clinical pictures of TSP in all high-incidence regions. The demonstration of IgG antibodies in serum and cerebrospinal fluid of patients with TSP in the Caribbean and Seychelles Islands, southern Japan, and the Ivory Coast indicate that the HTLV-I retrovirus could be the cause of this "tropical" myeloneuropathy.