mitochondrial symptomsadld leukodystrophymitochondrial cytopathyhypomyelinating leukodystrophymetachromatic leukodystrophy symptomsdemyelinating leukodystrophymitochondrial cardiomyopathymitochondrial dysfunction symptomscongenital leukodystrophymitochondrial encephalopathygloboid leukodystrophyleukodystrophy diagnosis