A 5-Year Follow-Up of Triple-Seronegative Myasthenia Gravis Successfully Treated with Tacrolimus Therapy

Seronegative myasthenia gravis (MG) is a generalized form of MG that is diagnosed on the basis of clinical symptoms, electrophysiological testing, and pharmacological responses, in the absence of a seropositive status for anti-acetylcholine receptor (AChR) antibodies. Generalized MG that is seronegative for anti-AChR, anti-muscle-specific kinase (MuSK), and anti-low density lipoprotein receptor related protein 4 (Lrp4) antibodies is known as triple-seronegative MG. We here describe a case of triple-seronegative MG in an 8-year-old boy. His first symptom was dysphagia, at 3 years of age, and he subsequently developed ptosis, rhinolalia, and a waddling gait. A genetic analysis was conducted to exclude the possibility of congenital myasthenia syndrome due to the patient's resistance to steroid therapy. His condition was successfully managed with tacrolimus therapy over a 5-year follow-up period. Recently, several studies have reported the therapeutic utility of tacrolimus in juvenile seropositive MG; in contrast, a few reports have described tacrolimus treatment in cases of seronegative MG. Our findings suggest that tacrolimus therapy is a safe and effective option for the treatment of juvenile seronegative MG.