| Motor regression | Loss of previously acquired motor skills |
| Hypotonia | Decreased muscle tone |
| Ataxia | Coordination difficulties |
| Spasticity | Muscle stiffness |
| Nystagmus | Involuntary eye movements |
| Visual impairment | Often due to optic atrophy |
| Seizures | Present in ~50% of cases |
| Cognitive decline | Progressive intellectual deterioration |
| Dystonia | Involuntary muscle contractions, often affecting neck and limbs |
| Parkinsonism | Tremor, bradykinesia, rigidity |
| Cognitive impairment | Variable, often mild |
| Psychiatric symptoms | Depression, anxiety |
| Databases | OMIMOrphanetClinicalTrialsPubMed |