Snapshot A 53-year-old man presents to urgent care with a sinus infection. It’s his third infection of the month. He has been feeling very fatigued lately, but attributed that to his multiple infections. Blood-work is obtained, showing leukopenia, along with anemia and thrombocytopenia. Physical exam reveals marked splenomegaly. A peripheral blood smear shows cells with hairy cytoplasmic projections. It stains with TRAP. Introduction Indolent leukemia of mature B-cells with infiltration of bone marrow and spleen Characteristics “hairy cells” with filamentous, hair-like projections tartrate-resistant acid phosphatase (TRAP +) Epidemiology Median onset 50-55 years of age Male > female 4.5x ETIOLOGY Associated conditions autoimmune conditions BRAF V600E mutation Presentation Symptoms pancytopenia from infiltration of bone marrow fatigue infections bleeding anemia Physical exam splenomegaly from infiltration of spleen may see hepatomegaly may see lymphadenopathy in 10% STUDIES Best initial test - peripheral blood smear B-cells with hairy projections + TRAP stain Most accurate test – flow cytometry CD11c+ and CD2+ CD5- and CD10- Bone marrow aspirate dry tap due to marrow fibrosis increased reticulin CBC anemia thrombocytopenia leukopenia Differential Diagnosis Non-Hodgkin lymphoma Mantle cell lymphoma Treatment If asymptomatic, just observe If symptomatic, treat first-line is purine analogs cladribine (2-CDA) pentostatin both inhibit adenosine deaminase recall this is the same enzyme deficiency seen in SCID leading to B-cell dysfunction if refractory, INFα or rituximab Complications Infections Increased risk of malignancy Prognosis Good prognosis, especially with good response to purine analogs Disease progression is slow