Updated: 12/24/2016

Hairy Cell Leukemia (HCL)

Review Topic
  • 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.  
  • Indolent leukemia of mature B-cells with infiltration of bone marrow and spleen
  • Epidemiology
    • median onset 50-55 years of age
    • male > female 4.5x
  • Associated conditions
    • autoimmune conditions
    • BRAF V600E mutation
  • Characteristics
    • “hairy cells” with filamentous, hair-like projections
    • tartrate-resistant acid phosphatase (TRAP +)
  • 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%
  • 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
  • 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
Prognosis, Prevention, and Complications
  • Prognosis
    • good prognosis, especially with good response to purine analogs
    • disease progression is slow
  • Complications
    • infections
    • increased risk of malignancy

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