Doctors of the University of West Indies, the Caribbean Epidemiology Center (CAREC) and the National Cancer Institute have been studying the epidemiology of HTLV-I and its role in the etiology and pathogenesis of adult T-cell leukemia/lymphoma (ALT), and aggressive T-cell lymphoma. The purpose of the current study is to evaluate familial and genetic aspects of ATL and its relationship to two other HTLV-I related conditions, HTLV-I associated myelopathy also known as tropical spastic paraparesis (HAM/TSP), and infective dermatitis. Enrollment of infective dermatitis cases was recently added and the disease entity is thought to be a harbinger for later development of either ATL or HAM/TSP. The purpose of this study is to interview patients with these conditions and perform laboratory studies (specifically, HLA and other viral or genetic studies) to better understand these diseases and their relationship to the HTLV-1 virus and the family history and genetic factors that may be involved as well.