HTLV‐I‐associated myelopathy

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Abstract
HTLV-I was first described as a pathogenic human retrovirus that causes adult T-cell leukemia (ATL). Soon after the discovery of HTLV-I, an association of this virus with a slowly progressive neurological disorder was found independently in Japan and Caribbean islands, and this new clinical entity (HTLV-I-associated myelopathy with tropical spastic paraparesis) was named HAM/TSP. Autopsy findings clarified the chronic inflammatory nature of the disease. Detailed neuropathological analysis demonstrated: (i) T-cell-dominant mononuclear cell infiltration; (ii) diffuse and symmetrical degeneration of the antero-lateral and inner portion of the posterior columns involving both myelin and axons; (iii) the presence of cytotoxic T cells and apoptosis of helper/inducer T cells; (iv) in vivo localization of HTLV-I provirus in the perivascular infiltrated T cells; and (v) accentuation of inflammatory lesions at the site with slow blood flow. From these findings it is suggested that a T-cell-mediated chronic inflammatory process targeting the HTLV-I-infected T cells is the primary pathogenic mechanism of HAM/TSP.