A Case Report of MuSK Antibody-Positive Myasthenia Gravis

Abstract

Myasthenia gravis (MG) is characterized by muscle weakness and fatigability. The presence of autoantibodies against the acetylcholine receptors (AChR) at the neuromuscular junction, which impairs neuromuscular transmission, is the hallmark of the disease. However, a minority of patients have antibodies against muscle-specific tyrosine kinase (MuSK), which is referred to as MuSK myasthenia gravis (MuSK-MG). We present the case of a 56-year-old female patient presenting with progressive dysphagia, slurred speech, and fatigable ptosis. She had a positive icepack test and a positive repetitive nerve stimulation test (RNST). Her AchR antibodies were negative, and the MuSK antibodies were positive. Her clinical response to pyridostigmine was unsatisfactory, but she had a good recovery with rituximab. Even though MuSK-MG is rare, it is an important diagnostic consideration, particularly in patients presenting with atypical symptoms or lacking AChR antibodies and in patients who have a poor response to conventional treatment. Acetylcholinesterase inhibitors, corticosteroids, immunosuppressants, and newer biologic agents targeting B cells are some of the treatments.