Pancytopenia is a decrease in all 3 peripheral blood lineages presenting as simultaneous anemia, leukopenia, and thrombocytopenia.

Acquired pancytopenia has many etiologies, but it is broadly grouped into 1 of 3 mechanisms causing decreased blood cell counts: bone marrow infiltration / replacement, bone marrow aplasia, or blood cell destruction or sequestration. Multiple mechanisms may occur simultaneously.

Bone marrow infiltration / replacement may be secondary to hematologic malignancy (such as lymphoma, myeloma, leukemia, myelodysplastic syndrome), myelofibrosis, metastatic disease, and infectious processes (tuberculous, fungal infection, etc). Bone marrow aplasia may be due to nutritional deficiencies, viral infection, immune destruction, drug effect, toxic exposures, or aplastic anemia. Blood cell destruction may occur due to ineffective hematopoiesis (ie, myelodysplastic syndrome), disseminated intravascular coagulation, or thrombotic thrombocytopenic purpura. Hypersplenism causes sequestration and is associated with various disease states (cirrhosis, lymphoma, autoimmune disorders, etc).