Familial Mediterranean fever (FMF) and multiple sclerosis: an association study in one of the world's largest FMF cohorts.

BACKGROUND AND
PURPOSE: To describe and characterize the association between familial Mediterranean fever (FMF) and multiple sclerosis (MS).
METHODS: The patient registry of The National Center for FMF was screened for the coexistence of FMF and MS. Tel-Hashomer criteria were used for the diagnosis of FMF, and FMF severity was evaluated, using the simplified FMF severity scale. McDonald criteria were used for the diagnosis of MS, and neurologic disability was measured using the expanded disability status scale (EDSS).
RESULTS: We identified nine patients, affected with both FMF and MS. The onset of the FMF averaged 15.6 (3-37) years. Most patients suffered from abdominal and joint attacks, and 50% of the patients sustained a moderate to severe FMF. The onset of the MS was at an average age of 31.6 (17-50) years. Neurologic manifestations varied individually, without a dominant deficit, and the course was in a relapsing-remitting pattern in most. The median EDSS was in general of low score (3.0), apart from the patients who were homozygous for the M694V mutation, in whom the MS was more severe. Based on our case series, the frequency of MS in our FMF population is 0.075%, twice higher the expected rate in the general population (P=0.0057).
CONCLUSIONS: Multiple sclerosis is more common in FMF than in the general Israeli population. Homozygosity for the M694V MEFV mutation may aggravate the phenotype of MS and predispose FMF patients to develop MS.