adld leukodystrophyhypomyelinating leukodystrophymetachromatic leukodystrophy symptomsdemyelinating leukodystrophymitochondrial leukodystrophycongenital leukodystrophygloboid leukodystrophyleukodystrophy diagnosisinfantile leukodystrophyleukodystrophy prognosismetabolic leukodystrophycerebral leukodystrophy