Introduction: We identified a subgroup of 20 patients with multiple sclerosis (MS) and psoriasis within a total group of 692 patients with MS.
Results: There was a high (80%) incidence of brainstem and/or cerebellar involvement and a high mean (+/-SD) Multiple Sclerosis Severity Score (6.06 +/- 2.88) in this subgroup. Of the patients who were human leukocyte antigen typed, 53% carried the MS-associated allele, DRB1*1501, and 27% carried the psoriasis-associated DRB1*07 allele.
Conclusion: The high incidence of brainstem and cerebellar involvement might be explained by the greater severity of MS and the high frequency (60%) of carriage of DRB1*04, DRB1*07, and/or DRB1*13 alleles, which are associated with brainstem and cerebellar involvement in MS.