Environmental factors in haemopoietic failure in humans

Aplastic anaemia can be defined as pancytopenia in the presence of a hypoplastic bone marrow and in the absence of leukaemia or malignant infiltration. Most cases have been attributed to an intrinsic defect in the pluripotential haemopoietic stem cell; however, stem cell suppression or a defect in the marrow environment would also produce the symptoms of aplasia. In vitro culture systems have been used to explore these possibilities and have provided evidence that the syndrome known as aplastic anaemia includes several distinct disease processes. These include primary failure of the haemopoietic stem cell and the suppression of stem cell function by cellular, humoral or other environmental factors. This heterogeneity provides the background for attempting to treat the disease by bone marrow transplantation, immunosuppression or stimulation of haemopoiesis.