[Reticular dysgenesis: primary disorder in differentiation of hematopoietic stem cells?]

Reticular Dysgenesis (RD) basically represents a lymphopenic severe combined immunodeficiency (SCID) in association with congenital agranulocytosis. It is presumed that RD results from a primary defect of pluripotent hematopoietic stem cells (HSC). Alternatively RD might be due to an alloreaction induced by T-cells derived from intrauterine transfusion of maternal cells into an immunoincompetent host. In the past 15 years, among 49 newborns with SCID taken care of in the University Hospital of Ulm, 5 children (4 boys, 1 girl) exhibited the characteristics of RD. In 3 of 4 cases studied, maternal T-cells were detected by HLA-typing. All 3 children showed signs of graft-versus-host-disease (GvHD), confirmed histologically. However, 9 of 45 newborns with SCID without congenital agranulocytosis also disclosed maternal T-cell-engraftment; 5 of the 9 had signs of GvHD. Therefore, it is unlikely that RD is caused by GvHD secondary to maternofetal transfusion. The fact that erythropoiesis, thrombopoiesis and the monocyte-macrophage-system basically are intact argues against a global maturation defect of HSC in RD.