Multiple sclerosis and amyotrophic lateral sclerosis: a human leukocyte antigen challenge.

Multiple sclerosis (MS) and amyotrophic lateral sclerosis (ALS) are two different central nervous system pathology that, according to the most accredited hypotheses, recognize a different etiopathogenesis. The simultaneous occurrence of MS and ALS is quite unusual. To our knowledge, only three cases have been so far described by clinical, laboratory, and post-mortem studies. We report four new cases of this peculiar combination that have been observed and are herein described, included their human leukocyte antigen (HLA) profile studies. On the basis that three out of four patients in our case series presented HLA-B*18:01A, we may hypothesize that this antigen could play a role in developing both diseases.