ABSTRACT
I) ETIOLOGY Aplastic anemia (AA) arises from failure of marrow to produce in sufficient quan
tities, all hematopoietic lineages including platelets, neutrophils and red blood cells (RBC). In most cases, AA is due to hematopoietic stem cell damage or a lack of stem cells. Frequendy, there is an immunologic component resulting in sup pression of hematopoiesis. Patients may present at any age, although it is often a disease of young people (median age 20-25 years). The annual European and North American incidence of AA is roughly 2 per 106 individuals. AA may be either ac quired or genetically determined (Table 6.1.1). If a drug etiology is suspected and exposure to several drugs has occurred, the most likely culprit would have been taken 6-8 weeks before onset of symptoms.
