Type 1 SMA | Inevitable by age 2 years | Marked | Severe | Full time ventilatory support required |
Type 2 SMA | ∼40% in childhood | Gradual | Moderate | Nocturnal ventilatory support required |
Type 3 SMA | Rare in childhood | Gradual | Rare in childhood | Occasional ventilatory support |
SMARD | High in first 6 months | Marked | Severe | Full time ventilatory support |
Duchenne MD | High After loss of ambulation | Gradual | After loss of ambulation | Cardiomyopathy may determine prognosis |
Ullrich congenital MD | 70% in adolescence or before | Gradual, may stabilise | Occasional | Marked contractures |
Rigid spine syndrome | Moderate | Gradual | Occasional | Can develop respiratory failure with preserved VC before loss of ambulation |
Nemaline myopathy | High risk in neonatal variant, may be late onset | Variable | In severe form | Highly heterogeneous disorder |
Myotubular myopathy | High in severe X-linked form | Marked | In severe form | Can be complicated by opthalmoplegia and hepatic haemorrhage |
Congenital myasthenia | Fluctuating may occur in neonatal period | Variable | Uncommon | Genotype links DOK-7 variant associated with stridor |
Mitochondrial myopathy | Common | Variable | Variable | |