The human T-lymphotropic virus, human T-cell lymphotropic virus, or human T-cell leukemia-lymphoma virus (HTLV) family of viruses are a group of human retroviruses that are known to cause a type of cancer called adult T-cell leukemia/lymphoma and a demyelinating disease called HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP). The HTLVs belong to a larger group of primate T-lymphotropic viruses (PTLVs).
To date, four types of HTLVs (HTLV-1, HTLV-2, HTLV-3, and HTLV-4) HTLV types HTLV-1 and HTLV-2 viruses are the first retroviruses which were discovered. Both belong to the oncovirus subfamily of retroviruses and can transform human lymphocytes so that they are self-sustaining in vitro.
HTLV-1 has been implicated in several kinds of diseases, including tropical spastic paraparesis, and as a virus cancer link for leukemia.
HTLV-2 is closely related to HTLV-1. HTLV-2 may be linked to Cutaneous T-cell lymphoma (CTCL).
HTLV-3 and HTLV-4 have been used to describe recently characterized viruses, discovered in rural Cameroon in 2005. Presumably, transmitted from monkeys to hunters of monkeys through bites and scratches.
There is some evidence that HTLV-1 is a causative agent of cutaneous T-cell lymphoma. HTLV-1 is also associated with a progressive demyelinating upper motor neuron disease known as HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP), characterized by sensory and motor deficits, particularly of the lower extremities, incontinence and impotence. Only 0.3 to 4% of infected individuals develop HAM/TSP, but this will vary from one geographic location to another. HTLV-1 is associated with a rheumatoid-like arthropathy, although the evidence is contradictory. In these cases patients have a negative rheumatoid factor. Studies from Japan demonstrated that HTLV-1 infection may be associated with an intermediate uveitis. At onset the patients present with blurred vision and floaters. The prognosis is favorable—the condition usually resolves within weeks.