Eosinophilic fasciitis-like disorder developing in the setting of multiple sclerosis therapy

Dimethyl fumarate received FDA approval in March 2013 for treatment of multiple sclerosis and has had a rapid uptake in the field due in large part to a favorable safety profile. Side effects of dimethyl fumarate include flushing, gastrointestinal discomfort, and peripheral eosinophilia. We report a case of eosinophilic fasciitis-like disorder occurring in the setting of oral dimethyl fumarate therapy. Eosinophilic fasciitis is rare and may be related to the peripheral eosinophilia known to occur with this medication.

We present a case of a 36-year-old male treated with oral dimethyl fumarate for 16 weeks who developed a bilateral eosinophilic fasciitis-like disorder of the thighs. Magnetic resonance imaging revealed a fluid collection in the fascial plane and histopathologic examination revealed an inflammatory infiltrate with dermal and subcutaneous edema and sclerosis consistent with eosinophilic fasciitis. We discuss studies reporting peripheral eosinophilia with fumaric acid medications as well as the literature exploring possible mechanisms.

With the anticipated widespread use of dimethyl fumarate for multiple sclerosis patients, it is important for practitioners to recognize the symptoms of eosinophilic fasciitis and be aware of a possible association of oral dimethyl fumarate treatment with the development of an eosinophilic fasciitis-like disorder.