Hairy Cell Leukaemia- A Rare Case Presented with Leukocytosis

Hairy Cell Leukaemia (HCL) is an uncommon disease accounting approximately 2% of all lymphoid leukaemias. Cytologically and immunophenotypically, it is indolent neoplasm of intermediate mature lymphoid cells. The neoplastic cells have oval nuclei with abundant basophilic cytoplasm having circumferential hairy projections involving peripheral blood and diffusely involving the bone marrow and splenic red pulp. It occurs more predominantly in middle aged to elderly adults with median age of 52 years; with male predominance (M:F=4:1). HCL was firstly recognised by Ewald in 1923 and described as Leukaemische reticuloendotheliose and term HCL was coined by Schrek and Donelly in 1966. A 75-year-old male known case of diabetes and hypertension with chronic kidney disease, visited to Outpatient Department (OPD) with history of severe fatigue and weight loss of 5kg in last one month. On physical examination; massive splenomegaly was found measuring 15 cm below left costal margin. Complete Blood Count (CBC) revealed Hemoglobin (Hb) of 10.9 gm%, Total Leucocyte Count (TLC) was 40,200/mm3 , Differential leukocyte counts were Neutrophils (N)07, Lymphocytes (L)11, Eosinophils (E)01, Monocytes (M)01 and 80% of atypical lymphoid cells and Platelets count 1.08 L/mm3 . Peripheral blood smear showed Red Blood Cells (RBCs) predominantly normocytic normochromic with mild anisocytosis and 80% of atypical lymphoid cells with hairy projections (hairy cells). On Contrast-Enhanced Computed Tomography (CECT), whole abdomen showed massive splenomegaly (size=27cm). Bone marrow aspiration examination was done showing low cellularity and comprising of 45% cells of HCL type and suggestive of HCL. On flow cytometry, immunophenotyping showed CD19, CD20, CD79b, CD11C, CD103, FMC-7, CD123, CD200 positive abnormal cells and confirming the diagnosis of classical HCL.