Which leukemias commonly present with pancytopenia?

Leukemias Commonly Causing Pancytopenia

Acute leukemias—particularly acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL)—are the primary leukemias that present with pancytopenia, with AML being the most common cause in adults. 1

Acute Leukemias

Acute Myeloid Leukemia (AML)

AML is the predominant leukemic cause of pancytopenia across multiple populations:

• Most common etiology in adults presenting with pancytopenia, accounting for 21.4% of cases in Iranian populations 2 and 17.9% in Western Indian tertiary centers 3
• Can present as aleukemic leukemia with pancytopenia as the sole manifestation, without circulating blasts in peripheral blood 4
• All AML subtypes can cause pancytopenia, including:
  • AML with recurrent genetic abnormalities (t(8;21), inv(16), t(15;17), etc.)
  • AML with myelodysplasia-related changes
  • Therapy-related AML
  • AML not otherwise specified 1

Acute Lymphoblastic Leukemia (ALL)

• Second most common acute leukemia causing pancytopenia
• Comprises 38.7% of pancytopenia cases in patients under 20 years 2
• In adults over 55, ALL accounts for approximately 20% of acute leukemia cases 5
• Can present with pancytopenia without fever or lymphadenopathy, particularly in B-lymphoblastic leukemia 5
• Both B-cell and T-cell ALL subtypes can present with pancytopenia 1, 6

Chronic Leukemias (Less Common)

Chronic Myeloid Leukemia (CML)

• Rarely presents with pancytopenia at diagnosis
• Severe anemia is uncommon; thrombocytosis is more frequent 7, 8, 7
• When pancytopenia occurs, consider:
  • Blast phase transformation (≥20% blasts) 7
  • Accelerated phase with cytopenias unrelated to therapy 7
  • Treatment-related cytopenias (transient, due to delayed recovery of normal hematopoiesis) 8

Chronic Lymphocytic Leukemia (CLL)

• Pancytopenia typically occurs from bone marrow infiltration causing cytopenia, not from elevated lymphocyte counts 9
• Diagnosis requires ≥5 × 10⁹/L clonal B lymphocytes, but cytopenia from marrow infiltrate establishes CML diagnosis regardless of lymphocyte count 9

Other Myeloid Neoplasms with Pancytopenia

Myelodysplastic Syndromes (MDS)

• Refractory cytopenia with multilineage dysplasia is a defining feature 1
• Accounts for 15% of pancytopenia cases in some series 3

Hairy Cell Leukemia (HCL)

• Classic presentation includes varying degrees of pancytopenia 10
• 39% of patients have absolute neutrophil count <0.5 × 10⁹/L at presentation 10
• 17% have active infection at diagnosis due to profound neutropenia and monocytopenia 10

Myeloid/Lymphoid Neoplasms with Eosinophilia

• Can present with pancytopenia despite prominent eosinophilia in some cases 11
• Includes neoplasms with PDGFRA, PDGFRB, FGFR1, JAK2, FLT3, or ABL1 rearrangements 11

Critical Diagnostic Pitfalls

1. Peripheral smear alone is insufficient: Aleukemic leukemia can show pancytopenia without blasts in peripheral blood despite 45% marrow infiltration 4

2. Bone marrow examination is mandatory: Required to differentiate between decreased production (leukemia, aplastic anemia) versus increased destruction (hypersplenism) 12, 4, 3

3. Age-specific patterns: In patients <20 years, ALL predominates; in adults >45 years, AML accounts for 53.5% of leukemic pancytopenia 2

4. Coexisting conditions: Cirrhosis with splenomegaly can mask underlying ALL, requiring high clinical suspicion with acute worsening of cytopenias 5