The recent history of Pelizaeus‐Merzbacher Disease (PMD) demonstrates paradigmatically the impact of basic biological research on clinical neurology and brain pathology: this rare and peculiar hereditary disease has become one of the best known disorders of its kind, through a cooperative research effort in neuropathology, human genetics, neurochemistry and molecular biology. PMD, a genetic dysmyelination restricted to the CNS, has been identified as a disease that involves the X chromosome‐linked gene for myelin proteolipid protein (PLP), a major structural myelin component. Today more than 30 different mutations in this gene have been defined and associated with PMD or the clinically distinct form X‐linked spastic paraplegia type‐2 (SPG‐2). Improved scanning techniques, specifically the non‐invasive magnetic resonance imaging (MRI), allow its early diagnosis in the heterogeneous group of CNS myelin deficiencies. These remarkable achievements have, at the same time, caused a problem for disease classification. Myelin disorders have been grouped in the past on the basis of clinical and neuropathological criteria, creating a system that has now to be reconciled with molecular
展开▼
