Hairy Cell Leukemia (HCL)

Snapshot

• A 50-year-old man presents to his primary care physician for an annual visit. He has no complaints. His past medical history includes hypertension, hypercholesterolemia, and rheumatoid arthritis. He goes for routine blood tests today, which reveals marked pancytopenia. A peripheral blood smear is done, showing cells with hair-like projections.

Introduction

• 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
• Characteristics
  • “hairy cells” with filamentous, hair-like projections
  • tartrate-resistant acid phosphatase (TRAP) + 
• Prognosis
• good prognosis, especially with good response to purine analogs

Presentation

• Symptoms
  • pancytopenia from infiltration of bone marrow
    • fatigue
    • infections
    • bleeding
    • anemia
• Physical exam
  • splenomegaly from infiltration of spleen
• no lymphadenopathy

Evaluation

• Peripheral blood smear
  • B-cells with hairy projections 
  • + TRAP stain (tartrate-resistant acid phosphatase)
• Flow cytometry
  • CD11c+ and CD2+
  • CD5- and CD10-
• Bone marrow aspirate
  • dry tap due to marrow fibrosis
• CBC
  • anemia
  • thrombocytopenia
• leukopenia

Differential Diagnosis

• Non-Hodgkin lymphoma 
• Mantle cell lymphoma

Treatment

• Purine analogs
  • first line: cladribine (2-CDA)
  • pentostatin
  • both inhibit adenosine deaminase
• recall this is the same enzyme deficiency seen in SCID leading to B-cell dysfunction

Complications

• Complications
  • infections
  • increased risk of malignancy