This spectrum of diseases can be broadly classified into four categories, each varying in severity:
- Connatal PMD stands as the most severe type, characterized by delayed mental and physical development alongside severe neurological symptoms.
- Classic PMD typically manifests with initial symptoms such as muscle weakness, involuntary eye movements (nystagmus), and motor developmental delays within the first year of life.
- Complicated SPG2 presents with motor development challenges and brain involvement.
- Pure SPG2 encompasses cases of PMD without neurological complications.
MRI analysis of the brain can reveal notable alterations in myelination levels. Other symptoms associated with PMD may involve sluggish growth, tremors, inability to achieve normal head movement control, and declining speech and cognitive abilities.