The HTLV-1 infects CD4+ T-lymphocytes and causes adult T-cell leukemia/lymphoma (ATLL)-a rare, yet aggressive hematological malignancy with high rates of therapy-resistance and generally poor clinical outcomes [30–32], in addition to several autoimmune/inflammatory conditions, including infectious dermatitis [33,34], rheumatoid arthritis [35,36], uveitis [37,38], keratoconjunctivitis [39], sicca syndrome [40,41], Sjögren’s syndrome [42,43], and HAM/TSP, among others [25,26,44–46]. This evidence concerns the gene CD4 and tropical spastic paraparesis.