Tacrolimus-related nocturnal myoclonus of the lower limbs in elderly patients with rheumatoid arthritis.

Tacrolimus is an effective and well-tolerated treatment for rheumatoid arthritis (RA). We report three cases of strictly sleep-associated myoclonus in RA patients treated with tacrolimus. Although the high-dosage administration of tacrolimus in transplantation is known to cause diverse neurotoxic adverse effects, including myoclonus, no previous cases of myoclonus in RA, especially in association with sleep, have been reported. We suggest that this is not a rare adverse effect, particularly in elderly RA patients.