Which RNA virus is specifically linked to hairy cell leukemia?

The correct answer relates to HTLV-1, a retrovirus that has been specifically linked to the development of hairy cell leukemia. Hairy cell leukemia is a rare form of chronic lymphoid leukemia characterized by the proliferation of abnormal B cells that have a distinctive morphology, often described as "hairy" due to the fine prolongations of cytoplasm.

HTLV-1 (Human T-lymphotropic virus type 1) is known to be associated with several hematological malignancies, most notably adult T-cell leukemia/lymphoma, but it has also been implicated in the pathophysiology of hairy cell leukemia. This association arises due to the virus's ability to induce genetic changes in host T cells, leading to malignancy.

Other options, while they are associated with various diseases, do not specifically link to hairy cell leukemia. HIV, for example, is primarily linked with immunosuppression and opportunistic infections, while HCV is closely associated with liver disease and hepatocellular carcinoma. HTLV-2 has been studied but lacks the same strong association with hairy cell leukemia as HTLV-1.

Given this information, HTLV-1 stands out as the RNA virus specifically tied to the pathogenesis of hairy cell leukemia