| Phenotype details |
age at deterioration 16y; developmental delay, intellectual disability; progressive psychomotor slowing adolescence/adulthood; no Rett-like features; dystonia; minimal Parkinsonism, only freezing of gait, hesitancy at doorway; l-DOPA responsive; limited expressive language; no sleep problems; staring, absence or atonic seizures; no ocular defects; T2 hypointense substantia nigra and globus pallidus (high iron); T1 hyperintense ‘halo’ midbrain; no cerebral atrophy; cerebellar atrophy |