A patient with a variant form of hairy cell leukaemia.

A 57-year-old woman was admitted because of weakness, fatigue, abdominal discomfort, easy bruising and splenomegaly. A highly elevated leukocyte count with hairy-cell-like cells was found, the cells being positive for the monoclonal antibodies CD19, FMC7, CD11c and B-ly-7 and negative for CD24 and CD25. Blood and bone marrow were investigated not only in our own laboratory but also in several other laboratories resulting in a variety of possible diagnoses. Only after combining all data could a definitive diagnosis of variant hairy cell leukaemia be made. The patient was treated initially with a splenectomy and later on with interferon-alpha-2b, resulting in a steady decrease in the leukocyte count. After a follow-up of 2 years a nearly complete remission was obtained with a good quality of life. The differential diagnosis of this rare disorder is discussed with emphasis on the relative contribution of different diagnostic procedures.