Polyarteritis nodosa (PAN) is a form of systemic necrotising vasculitis involving predominantly small- and medium-sized muscular arteries. Aetiological factors are usually unknown in the causation of polyarteritis nodosa, though some cases may be due to hepatitis B virus, cytomegalovirus, drug hypersensitivity, and malignancies. Hairy cell leukaemia (HCL) is characterised by pancytopenia, splenomegaly and inaspirable bone marrow. The coexistence of the two diseases is highly unlikely by chance, and it is hypothesised that an aetiological relationship exists between the two conditions.

Case report

A 37-year-old man presented with a one-week history of fever and oliguria. On examination, he had generalised lymphadenopathy and hepatosplenomegaly. Other systemic examination was normal.

Laboratory tests revealed pancytopenia; erythrocyte sedimentation rate (ESR) was 56 mm in the first hour. Bone marrow aspirate was dry-tap. Trephine biopsy showed hypercellular marrow spaces with characteristic features …