Which of the following cause tropical spastic paraplegia -

HTLV-I was isolated in 1980 from a T cell lymphoma cell line from a patient originally thought to have cutaneous T cell lymphoma. Serologic data have determined that HTLV-I is the cause of at least two impoant diseases: Adult T cell leukemia/ lymphomaATL and tropical spastic paraparesis, also called HTLV-I-associated myelopathy (HAM). HTLV-I may also play a role in infective dermatitis, ahritis, uveitis, and Sjogren's syndrome. HAM resembles multiple sclerosis in ceain ways. The onset is insidious. Symptoms include weakness or stiffness in one or both legs, back pain, and urinary incontinence. Sensory changes are usually mild, but peripheral neuropathy may develop. The disease generally takes the form of slowly progressive. (Harrison's Principles of internal medicine, 20 th edition, page 1504)