Primary lateral sclerosis may occur within familial amyotrophic lateral sclerosis pedigrees.

Primary lateral sclerosis (PLS) is considered to be a specific sporadic motor neuron disorder, but some reports have shown familial history of motor neuron disorders that may comprise PLS cases. Here we report a novel pedigree highlighting an intrafamilial occurrence of PLS and amyotrophic lateral sclerosis (ALS) cases. These observations strengthen the hypothesis that PLS may represent an ALS phenotype with a long evolution and strongly suggest the involvement of common genetic factors that can lead to upper and lower motor neuron death.