The role of HTLV-I in tropical spastic paraparesis in Jamaica.

We report clinical and laboratory investigations of 47 native-born Jamaican patients with endemic tropical spastic paraparesis and of 1 patient with tropical ataxic neuropathy. Mean age at onset was 40 years, with a female-male preponderance (2.7:1). Neurological features of endemic tropical spastic paraparesis are predominantly those of a spastic paraparesis with variable degrees of proprioceptive and/or superficial sensory impairment. Using enzyme-linked immunoabsorbent assay (ELISA), IgG antibodies to human T-lymphotropic virus type I (HTLV-I) were present in 82% of sera and 77% of cerebrospinal fluids. On Western blot analysis, IgG antibodies detected the p19 and p24 gag-encoded core proteins in both serum and cerebrospinal fluid. Titers were tenfold higher by ELISA in serum than in cerebrospinal fluid, and some oligoclonal bands present in fluid were not seen in serum. Serum-cerebrospinal fluid albumin ratios were normal, and IgG indexes indicated intrathecal IgG synthesis. Histopathological changes showed a chronic inflammatory reaction with mononuclear cell infiltration, perivascular cuffing, and demyelination that was predominant in the lateral columns. In 1 patient, a retrovirus morphologically similar to HTLV-I on electron microscopy was isolated from spinal fluid. Our investigations show that endemic tropical spastic paraparesis in Jamaica is a retrovirus-associated myelopathy and that HTLV-I or an antigenically similar retrovirus is the causal agent.