Hairy-cell leukaemia simulating connective tissue disease.

A patient is reported, in whom clinical and biochemical evidence of connective tissue disease preceded the diagnosis of hairy-cell leukaemia by at least 2 years. The pathogenetic mechanism(s) responsible for the coexistence of hairy-cell leukaemia with vasculitis and rheumatic disease is discussed. It is proposed that the 2 diseases may share a common predisposing factor, or that the hairy cells may elicit disturbances in immune homeostasis, implying a dysfunction of T suppressor cells. Hairy-cell leukaemia should be considered in the differential diagnosis in cases of unexplained febrile illness associated with pancytopenia and signs of connective tissue disease.