Aplastic anaemia with 'hot pockets'

4 patients with chronic severe aplastic anaemia and with persistent foci of intense haematopoietic activity, so-called 'Hot Pockets', in their bone marrow were studied. In all patients the remainder of the bone marrow was morphologically and erythrokinetically hypoplastic. The cellular morphology in these 'Hot Pockets' displayed megaloblastic features and definite maturation abnormalities in erythroblasts, but no consistent changes in the myeloid or megakaryocytic series. The presence of persistent 'Hot Pockets' presents a conceptual challenge since these pockets contain multipotential stem cells capable of differentiation and self-renewal, but obviously incapable of repopulation of the bone marrow. In view of additional evidence for dyserythropoiesis in aplastic anaemia such as changes in erythroblast morphology and the production of macrocytes, fetal haemoglobin and complement sensitive cells, it seems likely that the bone marrow of aplastic anaemia patients is totally dyserythropoietic rather than hypoactive and that bone marrow transplantation in many cases may be both justified and necessary.