Double trouble: A case of spinal muscular atrophy type III found to be complicated by myasthenia gravis due to subacute dysphagia

Abstract

Background: Spinal muscular atrophy (SMA) is a genetic disorder caused by the progressive loss of lower motor neurons. Myasthenia gravis (MG) is an acquired, autoimmune, neuromuscular junction disorder. We encountered a rare case of coexisting SMA and MG.Case Presentation: A man was diagnosed with SMA type III when aged in his 20s. At the age 71 years, he started experiencing difficulty flexing his elbow, with dysphagia appearing within a few months. He had difficulty eating and was referred to our hospital to undergo gastrostomy. Other diseases that could cause dysphagia were investigated.Tests for acetylcholine receptor antibody and edrophonium showed positive results, based on which he was diagnosed with MG. A genetic test was carried out that reconfirmed SMA. He was treated with intravenous methylprednisolone, pyridostigmine and tacrolimus, resulting in dysphagia gradually recovering and he could consume a full meal.The patient was discharged without undergoing gastrostomy.Conclusions: SMA type III is a disease manifesting as slowly progressive muscle weakness.When the muscle weakness progresses and dysphagia appears subacutely in SMA type III patients, it is necessary to consider the complications of other diseases, such as MG.