A Case of Variant Hairy Cell Leukaemia in Durable Complete Remission on Combination Therapy

A 50-year-old female presented with complaints of abdominal fullness, night sweats and loss of weight over 6 months with massive splenomegaly and pallor. Peripheral blood and bone marrow imprint smear revealed atypical lymphoid cells. Bone marrow biopsy showed a ‘fried egg appearance’ suggestive of hairy cell leukaemia. Bone marrow flow cytometry favoured the diagnosis of Variant hairy cell leukaemia. She was treated with standard 5-day course of Cladribine along with weekly rituximab for 8 weeks. There was regression of splenomegaly with improvement in anemia and sustained complete remission at 36 months. This case highlights the importance of distinguishing variant hairy cell leukaemia from the classical variety as it is more aggressive and needs addition of Rituximab to purine analogues to improve outcomes. Morphological similarity between these entities may lead to delay in diagnosis and inferior treatment. High index of suspicion is needed to initiate proper treatment and maximise outcomes.