Another heads up about this excellent, though very complex and technical, site. Just scanning through the comments you can discover some interesting thoughts:
These are puzzling cases indeed. Do these patients have ALS or a different clinical presentation of SCA2? How should we classify such patients? Intermediate repeat expansions have been identified as a genetic risk factor for ALS, while true (longer) expansions are encountered in rare sporadic and familial ALS cases and probably should be considered as a rare true cause of ALS. Thus, disease presentations of SCA and ALS within the same family are possible. That tallies with the concept that ALS is a clinical syndrome with heterogeneous etiologies, rather than a distinct disease entity.