Fig. 1

Bone Marrow Biopsy of HLH (a-d). The marrow showed trilineage hematopoiesis with relative granulocyte hyperplasia (M:E ratio 6.2:1). Erythroid and granulocyte precursors showed orderly maturation with no evidence of dyspoiesis or increased blasts. Megakarycoytes were adequately present and show normal morphology. Lymphocytes and plasma cells were unremarkable. Macrophages were mildly increased with evidence of hemophagocytosis and show frequent forms with ingested mature red cells, erythroid precursors, occasional leukocytes and platelets. Arrows indicate sections associated with hemophagocytosis