Co-occurrence of MS and ALS: a clue in favor of common pathophysiological findings?

Amyotrophic lateral sclerosis (ALS) and multiple sclerosis (MS) are two neurological disorders that seem, theoretically, completely divergent according to epidemiological, clinical, pathophysiological, and therapeutic data. However, some reports that have mentioned the occurrence of both conditions within the same patient underpin the suggestion that this co-occurrence might not be random. We report six co-occurrences of ALS and MS cases, focusing on epidemiological and clinical diseases findings. We then compare our cohort to those in the literature. Our cohort was composed of five females and one male. The age of onset for MS ranged from 27 to 54 years with either primary or secondary prominence while all being progressive. Both diseases occurred sequentially in all but one the cases. Concerning ALS, the age of onset ranged from 51 to 60 years and the site of onset was the legs in 5/6 cases. The disease lasted from four to 29 months. Although infrequent, this co-occurrence supports the hypothesis of common, pathophysiological mechanisms between ALS and MS. We discuss some arguments favoring a potential link between both conditions.