Delayed high-grade atrioventricular block requiring pacemaker implantation in a multiple sclerosis patient treated with fingolimod.

Fingolimod is a sphingosine-1-phosphate 1 (S1P1) modulator which retains lymphocytes in secondary lymphoid organs and is approved for the treatment of relapsing multiple sclerosis (MS). The decrease of heart rate and AV block are reversible side-effects of treatment initiation. We report a case of persistent high-grade atrioventricular (AV) block 450 days after start of fingolimod and permanent pacemaker requirement in late-onset relapsing multiple sclerosis (MS). We discuss emerging risk factors for cardiac conduction deficits including the recently discovered vagomimetic effects of S1P1 modulation, structural brain and spinal cord damage, ageing and comorbidities.