Ionizing radiation
Hypocellular marrow
Arsenic
Benzene
WBC <500
Pancytopenia
Chemotherapy agents
Antibiotics (chloramphenicol)
Can progress to Myelodysplasia then to Leukemia
Pesticides- organochlorine, lindane
50% Fatality rate b4 BM transplant
Reticulocytes < 1%