A girl with Hurler disease (MPS IH) underwent allogeneic stem cell transplantation at 13 months of age with her one HLA-B antigen mismatch mother as donor. The procedure was complicated by cerebral hemorrhage and a ventricular-peritoneal shunt device was inserted. Mild GVH reactions were rapidly reversed. One year after transplantation ventriculitis was suspected and the shunt was replaced by a ventricular drainage catheter. Antibiotics had no effect and graft-versus-host disease (GVHD) was diagnosed. All symptoms were reversed by prednisolone and cyclosporine. Increased albumin and pleocytosis in the cerebrospinal fluid (CSF) normalized concomitantly. Electron microscopy of the CSF sediment showed debris consisting of numerous complex aggregates of thin lamellae and electron dense fragments with a tight lamellar texture. Biochemical analysis of the CSF sediment proved that the debris contained galactosylceramide and sulfatide. The electron microscopic and biochemical findings were interpreted to represent stripping of central myelin as a result of subacute GVHD in the central nervous system and its desquamation from the brain parenchyma into the ventricular CSF through the post-hemorrhage defect. From reversal of the GVHD at 2 years of age until follow-up at 10 years of age the clinical condition remained stable with no recurrence or deterioration.