1. Candidates for participation in the protocol will be patients of all ages with clinical and radiographic signs of leukodystrophy who do not have a specific etiology despite a previous comprehensive workup. The preceding investigation would have excluded the following: adrenoleukodystrophy, adrenomyeloneuropathy, metachromatic leukodystrophy, Krabbe disease, Canavan disease, a well-defined amino acid organic acid disorder, or a systemic mitochondrial cytopathy.