Multiple sclerosis and amyotrophic lateral sclerosis: is there a link?

To date, there are no reports studying the rate of amyotrophic lateral sclerosis (ALS) in relatives of multiple sclerosis (MS) patients and vice versa. This study was designed to look into this issue using two population-based databases of MS and ALS in Isfahan province of Iran. We have searched for any first, second or third degree familial kinship between the Isfahan MS Society database and Isfahan ALS population. We compared the rate of ALS among the population of first degree relatives of MS patients, with the crude prevalence of ALS in the general population of Isfahan. On the other hand, a reverse analysis was carried out to compare the prevalence of MS in Isfahan with its rate amongst the first degree relatives of ALS patients. We found 10 families among which five had first degree kinship. The rate of the diseases was significantly higher in both comparisons among the family members (p < 0.00001) and an odds ratios of more than 67 in both calculations showed a several-fold increase of ALS occurrence in the first degree relatives of MS patients and vice versa. In our study relatives of MS patients were significantly more prone to ALS and vice versa. This could give clues about the common features that the two disease share. Both diseases have an environmental and genetic component and these results mostly point toward genetic similarities.