A Case of Hairy Cell Leukemia Variant: Literature Analysis With Focus on Unmet Needs.

Hairy cell leukemia variant (HCLv) is a sporadic, B-cell non-Hodgkin lymphoma classified under chronic lymphoproliferative disorders. HCLv usually presents with easy fatigue, dragging pain abdomen, anemia, splenomegaly, hepatomegaly, initially leukocytosis followed by leucopenia, hairy cells in the smear and bone marrow, and an increased risk of infections. There is hypercellular bone marrow, and cytopenias are secondary to hypersplenism. It is essential to differentiate HCL from disorders like classic hairy cell leukemia (HCLc), splenic marginal zone lymphoma, and splenic diffuse red pulp lymphoma, as these are biologically different, with divergent approaches and outcomes. HCLv is poorly responsive or primary refractory to standard purine analogs cladribine or pentostatin. It has lower response rates to even cladribine and rituximab combination, a standard of care for classic HCL with very good response rates. Here, we present a case of an elderly male who presented with splenomegaly and leukocytosis, diagnosed as HCLv, and was treated with a cladribine and rituximab-based regime but showed residual cells in bone marrow on flow cytometry at six months post-treatment. There were no residual cells in peripheral blood in flow cytometry. Various aspects of the disease are discussed here with a detailed literature analysis. There is a definite unmet need for research on better treatment options in HCLv to improve its overall outcome.