| Prevalence | Very rare, estimated 1-3% of all ALS cases |
| Age | Typically presents in middle to older adults (50-70 years) |
| Sex | Slight male predominance |
| Course | Indolent progression over many years |
| Survival | Generally favorable; often decades-long disease course [@lavers2020] |
| Distal muscles | Tibialis anterior, peroneal muscles → foot drop |
| Proximal muscles | Quadriceps, hip flexors (later stage) |
| Symmetry | Relatively symmetric from onset |
| Gait | Steppage gait pattern, frequent tripping |
| Sporadic | Most cases are sporadic |
| SOD1 mutations | Occasional familial cases |
| [C9orf72](/entities/c9orf72) expansions | Less common than in classic ALS |
| Databases | OMIMOrphanetClinicalTrialsPubMed |
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