Table 2 Differential diagnosis between ALS and KD. The interpretation of these simple criteria must be put in perspective with the phenotypic heterogeneity of these two pathologies and more particularly of ALS (adapted from Pradat, 2014)
| Sex and age | KD | ALS |
|---|---|---|
| Adult man in his thirties or forties | Adult man or woman in their fifties or sixties | |
| Genetic | X-linked transmission Family history found in 2/3 of the cases | Familial in 10% of cases (autosomal dominant, recessive, multigenic, exceptionally X-linked) |
| Neurologic signs | ||
| Limb involvement | ||
| Topography Predominance in LL vs UL Proximal vs distal | Symmetrical LL more affected Proximal predominance | Most often asymmetrical LL = UL Proximal = distal |
| Pyramidal syndrome | Absent | Present in most patients |
| Bulbar involvement | ||
| Fasciculations | Lingual quasi constant lips, chin, or perioral area (often with a myokymic appearance). | Lingual frequent |
| Lingual atrophy | Present with a reshaped aspect | Present |
| Dysarthria and dysphagia | Moderate, contrasting with the severity of lingual atrophy and slowly progressive | Evolutive (frequent use of assistive devices for communication and enteral nutrition) |
| Pseudo-bulbar involvement | absent | possible |
| Cognitive involvement | Absent or very slight | Association with fronto-temporal dementia in 5–10% of the cases. |
| Respiratory insufficiency | Rare | Common |
| Progression | Slow Normal life expectancy | Rapid (but slow progressive forms) Median survival of 3 years |
| Gynecomastia | Frequent | Absente |
| ENMG | Chronic motor denervation associated with a decrease of sensory potentials | Motor denervation with frequent signs of activity (fibrillation) and normal sensory potentials |
| CPK | Important elevation | Elevation |