Coexistence of anti-MuSK antibody-positive myasthenia gravis and rheumatoid arthritis

Amber Eker,Mehtap Tınazlı,Senem Ertugrul Mut

doi:10.1186/s41983-020-00222-y

Abstract

BackgroundRheumatoid arthritis (RA) is an autoimmune disease characterized with symmetric synovitis and occasional extra articular involvement; also, some neurologic disorders can be observed during the disease course. Myasthenia gravis (MG) is one of them and it is an autoimmune disease of neuromuscular junction. It is caused by autoantibodies against neuromuscular junction proteins: the nicotinic acetylcholine receptor (AChR) and the muscle specific tyrosine kinase (MuSK). Very few studies have reported the associated autoimmune disorders in MuSK-MG. Here, we present the first patient who has MuSK antibody-positive MG gravis and rheumatoid arthritis.Case presentationA 53-year-old woman with RA presented with fatigue and fluctuating proximal muscle weakness. Her electroneurophysiological investigation resembled MG. Her AchR antibody level was normal but MuSK antibodies were high. After the acute treatment with plasmapheresis which lead to complete recovery in myasthenic symptoms, she is following with mycophenolate mofetil.ConclusionsConcomitant autoimmune disorders are common in the population. MG should be considered in patients with an autoimmune disorder and developing new neuromuscular weakness.

Highlights

Rheumatoid arthritis (RA) is an autoimmune disease characterized with symmetric synovitis and occasional extra articular involvement; some neurologic disorders can be observed during the disease course
Concomitant autoimmune disorders are common in the population
Myasthenia gravis (MG) should be considered in patients with an autoimmune disorder and developing new neuromuscular weakness

Summary

Background

It is reported that at least one or more autoimmune disorders may affect 5% of the population [1]. Rheumatoid arthritis was diagnosed according to 2010 American College of Rheumatology/European League Against Rheumatism Classification Criteria for RA by using a combination of her clinical, laboratory, and imaging features [8]. She said that she only used methotrexate for her arthritis treatment until her recent admittance; the vital signs were normal. Stimulating single-fibre electromyography in right extensor digitorum communis revealed significant jitter which represents neuromuscular junction disorder (Fig. 1b) Her anti-acetylcholine receptor (AChR) antibody level was normal but anti-muscle-specific tyrosine kinase (MuSK) antibodies were high (1.82 nmol/L; normal < 0.05 nmol/L). After the acute treatment of the symptoms, we observed complete recovery in myasthenic symptoms and we started oral steroid which was reduced and switched by mycophenolate mofetil

Discussion

Conclusion

Findings

Funding None