Muscle atrophy in muscle-specific tyrosine kinase (MuSK)-related myasthenia gravis.

Myasthenia gravis (MG) with muscle-specific tyrosine kinase (MuSK) antibody (MuSK-MG) is often associated with prominent facial and bulbar muscle atrophy. It remains unclear whether the muscle atrophy is a consequence of long-term corticosteroid treatment, or of the disease process per se. Herein, we report a steroid-naive patient with MuSK-MG who presented with severe weakness and marked atrophy of the facial and tongue muscles.