| Prevalence | Due to its rarity and diagnostic variability, precise incidence data are limited. Estimates range from 0.02–0.04 per 100,000 person-years in population-based studies. |
| Proportion of MND | PMA represents approximately 2.5–11% of all adult-onset Motor Neuron Disease cases. |
| Sex | Strong male predominance with a male-to-female ratio of approximately 4–5:1 (compared to ~1.5:1 in classic ALS). |
| Age at onset | Typically in the 5th–6th decade, though onset can range from the 3rd to 8th decade. Mean age at onset is approximately 50 years. |
| Geographic distribution | No clear geographic clustering, though ascertainment varies by diagnostic criteria used. |
| protein-aggregation | Accumulation of ubiquitinated inclusions in anterior horn cells. |
| Selective motor neuron vulnerability | Preferential degeneration of alpha motor neurons in the ventral horn of the spinal-cord, with relative sparing of oculomotor and Onuf's nucleus neurons. |
| oxidative-stress | Elevated markers of oxidative damage in degenerating motor neurons [@research]<!-- --> [@riku2014]. |
| neuroinflammation | Activated microglia contribute to motor neuron damage |
| [SOD1](/genes/sod1) mutations | Rare cases of PMA have been associated with SOD1 mutations, particularly those associated with LMN-predominant ALS phenotypes (e.g., A4V, D90A). |
| [C9orf72](/genes/c9orf72) | Hexanucleotide repeat expansion in C9orf72 has been identified in some PMA patients, particularly those with LMN-predominant presentations and FTD features. |
| [FUS](/genes/fus) | Mutations occasionally associated with PMA phenotype, especially in younger-onset cases with basophilic inclusion body disease. |
| Databases | OMIMOrphanetClinicalTrialsPubMed |