In a 30-year-old woman with hemoglobin 9.8 g/dL and platelet count 20 × 10⁹/L (no leukocyte count reported), can this be classified as bicytopenia?

Can This Be Classified as Bicytopenia?

Yes, this presentation with hemoglobin 9.8 g/dL and platelet count 20 × 10⁹/L definitively qualifies as bicytopenia, specifically anemia with thrombocytopenia, which is the most common pattern of bicytopenia accounting for 61% of cases. 1

Definition and Classification

• Bicytopenia is defined as the reduction of any two of the three major blood cell lines: erythrocytes, leukocytes, or platelets. 1

• This patient demonstrates clear reduction in two lineages:

  • Anemia: Hemoglobin 9.8 g/dL (below normal threshold of 11 g/dL for women) 2
  • Thrombocytopenia: Platelet count 20 × 10⁹/L (severely below normal threshold of 100 × 10⁹/L) 2

• The absence of a reported leukocyte count does not preclude the diagnosis of bicytopenia, as only two affected cell lines are required by definition. 1

Clinical Context from WHO Classification

• The WHO classification explicitly recognizes bicytopenia as a valid presentation in myelodysplastic syndromes, noting that "bicytopenia may occasionally be observed" in refractory cytopenias with unilineage dysplasia (RCUD). 2

• The footnote in the WHO MDS classification specifically states: "Bicytopaenia may occasionally be observed. Cases with pancytopaenia should be classified as MDS-U." 2 This confirms that bicytopenia is a recognized hematologic entity distinct from pancytopenia.

Diagnostic Implications

• Anemia with thrombocytopenia (the pattern seen here) is the most prevalent bicytopenia combination, representing 61% of all bicytopenia cases, followed by anemia with leukopenia (26%) and leukopenia with thrombocytopenia (13%). 1

• The severity of thrombocytopenia in this case (20 × 10⁹/L) is particularly concerning and warrants urgent evaluation, as platelet counts below 100 × 10⁹/L are used as diagnostic thresholds in multiple hematologic classification systems. 2

Critical Next Steps

• Obtain a complete white blood cell count with differential immediately to determine if this is actually pancytopenia rather than bicytopenia, as this distinction significantly impacts differential diagnosis and management. 1

• The most common etiologies of bicytopenia are non-malignant conditions (56%), followed by infectious causes (31.7%), malignant conditions (8.3%), and drug-induced causes (4%). 1 Among non-malignant causes, megaloblastic anemia is predominant, closely followed by immune thrombocytopenic purpura and alcoholic liver disease. 1

• Examine the peripheral blood smear for morphologic abnormalities including dysplastic features, schistocytes, or megaloblastic changes to guide further workup. 3, 4

• Obtain reticulocyte count to distinguish between decreased production (low reticulocyte count suggesting bone marrow failure, megaloblastic anemia, or MDS) versus increased destruction (high reticulocyte count suggesting hemolysis or bleeding). 3, 4

Common Pitfalls to Avoid

• Do not assume bicytopenia is benign without bone marrow examination if initial workup does not reveal a clear reversible cause, as 8.3% of bicytopenia cases are due to hematologic malignancies. 1

• Severe iron deficiency can paradoxically present with pancytopenia or bicytopenia including thrombocytopenia, contrary to the typical association with thrombocytosis. 5 Check iron studies including serum ferritin, serum iron, and total iron-binding capacity. 4

• Signs such as lymphadenopathy, splenomegaly, and hepatomegaly are most significantly associated with hematological malignancies (p < 0.001), while pallor, bleeding, hepatomegaly, and splenomegaly are most frequent in non-malignant conditions (p < 0.001). 1