Pancytopenia

Pancytopenia is a simultaneous reduction in red blood cells, white blood cells, and platelets. It is a finding, not a final diagnosis. The immediate risk depends on which cell line is most compromised: reduced red-cell mass limits oxygen delivery, neutropenia weakens host defence, and thrombocytopenia impairs primary hemostasis. The same pattern can arise through different mechanisms. The marrow may produce too few cells, abnormal cells may replace normal marrow, or circulating cells may be destroyed, consumed, or sequestered. Aplastic anemia is a production-failure disorder in which hypocellular marrow cannot maintain the blood-cell lines. Immune-mediated injury to hematopoietic stem and progenitor cells is an important acquired mechanism. The marrow is markedly hypocellular with fatty spaces rather than crowded by blasts or fibrosis, so infection, bleeding, and symptomatic anemia can occur together. Severe aplastic anemia requires marrow cellularity below 25%, or cellularity from 25% to 50% with less than 30% residual hematopoietic cells, plus at least two of the following: - ANC below 0.5 × 10⁹/L - platelet count below 20 × 10⁹/L - absolute reticulocyte count below 60 × 10⁹/L Very...