Myasthenia gravis and muscle atrophy

Muscle atrophy is uncommon in myasthenia gravis. There are some reports in the literature of muscle atrophy in MUSK-positive myasthenia gravis. The authors present eight cases of AChR-positive myasthenia gravis associated with muscle atrophy. Symmetrical atrophy of the forearms with preserved hand muscles was identified in six cases and scapular winging in two cases. Atrophy appeared 3-18 years after the onset of myasthenia gravis and after a period of progression, the condition was stabilized. In all cases, there were no pain syndrome, no sensory loss, normal creatine phosphokinase (CPK) levels, no significant abnormality on MRI of the cervical spine. Concomitant neuropathies, amyotrophic lateral sclerosis and other neuromuscular diseases were excluded. All patients underwent quantitative electromyography and repetitive nerve stimulation. The authors suggest that the atrophy is not the sign of myasthenia gravis in this case and is caused by other neuromuscular diseases.