HTLV-I-Associated Myelopathy

HLTV-I-associated myelopathy is a chronic inflammatory disease of the spinal cord associated with immunological abnormalities related to HTLV-I infection. The clinical features are characterized by slowly progressive spastic paraparesis and positive anti-HTLV-I antibody both in serum and in cerebrospinal fluid.¹² The association of spastic paraparesis with human T-lymphotropic virus type I (HTLV-I) was demonstrated independently in two different areas: the Caribbean Basin³ and Japan.⁴ In tropical spastic paraplegia, 59% of patients have antibodies to HTLV-I. In Japan, an association of HTLV-I with spastic paraparesis has been found, but these patients resided in a temperate zone. We proposed the term HTLV-I-associated myelopathy (HAM). Occurrence of such patients in Japan suggests HTLV-I as a cause of spastic paraparesis because Japan is one of the most endemic areas in the world for adult T-cell leukemia-lymphoma (ATLL) caused by HTLV-I; moreover, Japan is free from malnutrition and yaws, which have been considered possible causes of tropical spastic paraparesis. Investigators in other areas of the world have also found a similar association between HTLV-I and myelopathy (Fig. 11.1). Tropical spastic paraparesis and HTLV-I-associated myelopathy are thought to be the same disorder. At least 3100 patients with HAM have been reported worldwide, the highest prevalence being in the Caribbean and Japan (Table 11.1).