Recent literature suggests that a subgroup of Hairy Cell Leukemia(HCL), sometimes called Variant Hairy Cell(HCL-V) may in fact be a different type of Lymphoma and not Hairy Cell, and that it may respond to rituximab to a much higher extent than common Hairy Cell does. It is what was called Leukemic Reticuloendotheliosis in the past. It accounts for approximately 0.4% of chronic lymphoid malignancies and 10% of all HCl cases. In contrast to HCl-C, HCl-V is a more aggressive disease and according to the new WHO classification it is no longer considered to be biologically related to HCl-C. Patients with HCl-V have an elevated white blood count, easy-to-aspirate bone marrow (unlike HCL) and weak reactivity to tartrate – resistant acid phosphatase (TRAP). HCl-V cells are positive for CD103 and CD11c and negative for CD25. The HCl-V cells express also the B-cell antigens, CD19, CD20 and CD22. The HCl-V patients frequently have an unmutated Ig gene configuration. Currently, the principles of therapy for this rare disease derive from uncontrolled single institutional studies, or even single case reports. In contrast to HCl-C, the HCl-V respond to purine nucleoside analogs (PNA) but response is limited to partial responses in approximately 50% of patients. However, complete responses were observed in some patients treated with rituximab and anti-CD22 immunotoxins.
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