Hairy cell leukaemia.

Hairy cell leukaemia is a rare form of lymphoproliferative disease that affects 2% of leukaemia patients and was first described in 1958 as leukaemic reticuloendotheliosis. The typical presentation is pancytopenia, splenomegaly and abnormal lymphoid cells in blood with hairy cytoplasmic projections. The pathological hairy cell resembles in many ways B-lymphocyte as in chronic lymphocytic leukaemia (CLL). The disease occurs predominantly in older males, median age 50 years, and male/female ratio is 4:1. It is important to differentiate it from CLL because of its different behaviour and management.