The mechanism of pancytopenia involves either haemopoiesis itself, decreasing blood cell productions in number (aplastic anemia), haemopoietic stem cells are displaced by malignant cells (Leukemia, lymphoma, MDS) or they are being pooled (sequestrated) (spleen)/destroyed (immune) outside bone marrow. The mechanisms for pancytopenia differ according to the
etiology. For example, in
hemophagocytic lymphohistiocytosis (HLH) there is marked inappropriate and ineffective
T cell activation that leads to an increased hemophagocytic activity. The T cell activated
macrophages engulf erythrocytes, leukocytes, platelets, as well as their
progenitor cells. Along with pancytopenia, HLH is characterized by
fever,
splenomegaly, and hemophagocytosis in
bone marrow,
liver, or
lymph nodes. == Diagnosis ==