Dimethyl fumarate in a patient with multiple sclerosis and type 1 diabetes mellitus: The importance of ketonuria

Background: Dimethyl fumarate (DMF) is approved for use in patients with relapsing-remitting multiple sclerosis (MS). Its mechanism of action is still not well understood, but besides the immunological pathways in MS, it may also affect the metabolism of normally functioning internal organs, tissues and cells. Case presentation: We report on the case of 29-year-old woman with satisfactorily-controlled type 1 diabetes (T1D), who was diagnosed as having MS. After administration of DMF she experienced intense, adverse gastrointestinal reactions together with ketonuria up to 160 mg/dL. The highest ketone concentrations in the urine were observed approximately 2 h after each DMF dose and always with co-existing adverse reactions. Dose reduction did not improve symptoms and treatment had to be stopped. Twelve hours after the last dose of DMF all laboratory results returned to normal ranges and all gastro-intestinal adverse reactions were resolved within the following 24 h. Conclusion: This is a first report of ketonuria in a MS-patient with T1D treated with DMF. Patients with MS and co-existing metabolic diseases, which are not contraindicated for DMF treatment, represent a unique opportunity to address questions regarding the possible mechanisms of action of DMF on the cellular metabolism. The use of DMF in patients with metabolic diseases needs closer attention.