The major forms of benign hematologic conditions are anemia, neutropenia, transfusion reactions, Gaucher disease, and porphyria. Anemia is a sign of disease rather than a disease itself. Anemia results from 1 or more of 3 pathologic mechanisms: inadequate production of red blood cells (RBCs) by the bone marrow, blood loss, or premature destruction of RBCs. The major causes of neutropenia include hematologic neoplasm, metastatic neoplasm involving the marrow, irradiation, vitamin B12 deficiency and folate deficiency, drugs, infections, congenital or acquired primary disorders of hematopoiesis, autoimmune neutropenia, hypersplenism, hemodilution, and benign idiopathic neutropenia. The porphyrias are enzyme disorders that are autosomal dominant with low disease penetrance, except for congenital erythropoietic porphyria, which is autosomal recessive, and porphyria cutanea tarda, which may be acquired and is associated with hepatitis C and hemochromatosis.