MFN2 and amyotrophic lateral sclerosis: Indeed, despite median survival in amyotrophic lateral sclerosis spanning between 2 and 4 years, individual courses may show high variability, especially for atypical phenotypes.2 Clinical symptom presentation in MFN2-amyotrophic lateral sclerosis patients was quite heterogeneous, with the majority exhibiting spinal onset, although upper limb onset and pseudobulbar palsy were also reported.