Body Composition Findings During Weight Loss Observed in Fingolimod-Treated Relapsing-Remitting Multiple Sclerosis

Fingolimod is a sphingosine-1-phosphate receptor modulator widely used in the treatment of relapsing-remitting multiple sclerosis (RRMS). Clinically significant weight loss during fingolimod therapy has rarely been characterized in detail, particularly regarding body composition findings and the relative contribution of adipose tissue loss.

We report a 54-year-old man with RRMS who developed progressive, unintentional weight loss during fingolimod therapy. Over ∼2 years, body weight decreased from 100 to 78 kg without appetite loss, dietary restriction, increased physical activity, or major lifestyle changes. Extensive multidisciplinary evaluation did not identify malignancy, chronic infection, gastrointestinal disease, endocrine abnormalities, or systemic inflammatory disorders. Multifrequency bioelectrical impedance analysis demonstrated low adipose tissue parameters with relative preservation of skeletal muscle mass and hydration status, suggesting that adipose tissue reduction represented a major component of the observed weight loss pattern. Body weight subsequently remained stable during additional clinical follow-up.

This case describes progressive unintentional weight loss during fingolimod therapy in a patient with RRMS, with body composition findings suggesting predominant adipose tissue involvement. Although causality cannot be established from a single observation, the temporal association and exclusion of major alternative etiologies suggest a possible association that may merit further investigation. This report also highlights the potential value of body composition assessment in patients presenting with unexplained weight loss during fingolimod therapy.