[Differential diagnosis of reactive cytopenias]

Reactive cytopenias are a frequent cause for bone marrow investigations, including bone marrow trephine biopsies, especially if clinical examination and laboratory analyses (e.g., detection of substrate deficiencies) cannot provide a sufficient explanation. The evaluation of such biopsies is primarily concerned with the exclusion of diseases that displace the normal hematopoiesis (infiltrates of acute leukemias or lymphomas and metastases), the exclusion of a myelodysplastic syndrome that classically results in ineffective hematopoiesis, or the detection of specific diseases, particularly infectious or histiocytic diseases (e.g., hemophagocytic lymphohistiocytosis).In this review, we describe characteristic morphologic changes of reactive cytopenias, focus on specific infectious and noninfectious clinical pictures, and distinguish them from malignant changes, especially myelodysplastic syndrome and underlying leukemia of large granular T lymphocytes. Drug-induced changes in hematopoiesis are described in another article in this issue.