X-LINKED LYMPHOPROLIFERATIVE DISEASE IN A UNITED-KINGDOM FAMILY

X linked lymphoproliferative disease (XLP; Duncan's disease) is a rare disorder affecting boys and characterised by a defective immune respo nse to Epstein-Barr virus caused by a mutation in a gene located at ch romosome Xq25. Three siblings with XLP in a single UK family are repor ted and the variation in phenotypic expression of the disease in these siblings described. One of the siblings with life threatening fulmina nt infectious mononucleosis was successfully treated by chemotherapy, followed by bone marrow transplantation using an unaffected brother as the donor. A healthy baby boy recently born into the family was ident ified as carrying the defective maternal X chromosome using molecular genetic linkage analysis. This family illustrates the extent of presen t understanding of this often fatal condition.