# A Case Report of MuSK Antibody-Positive Myasthenia Gravis

## TL;DR

This case report describes a rare form of myasthenia gravis caused by MuSK antibodies and highlights the importance of proper diagnosis and treatment.

## Contribution

The paper presents a rare clinical case of MuSK antibody-positive myasthenia gravis with a successful response to rituximab.

## Key findings

- The patient had MuSK antibodies and atypical symptoms like dysphagia and slurred speech.
- Pyridostigmine was ineffective, but rituximab led to significant clinical improvement.
- MuSK-MG should be considered in patients with negative AChR antibodies and poor response to standard treatment.

## 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.