A case of SBMA presenting with myasthenic syndrome limited to a dropped head

Abstract

A 76‐year‐old man with spinal and bulbar muscular atrophy (SBMA) developed an acute course of the dropped head with diurnal fluctuations that worsened in the evening. He was diagnosed with myasthenic syndrome based on a decreased response to repeated stimulation, as well as increased jitter and blocking on single‐fiber electromyography, indicating disturbed neuromuscular transmission. Dropped head symptom was successfully alleviated and maintained by immunotherapy. Although limited reports are available on SBMA cases accompanied by myasthenic syndrome and on the clinical impact of impaired neuromuscular transmission on SBMA, myasthenic syndrome may be a common condition and even a part of the phenotypic spectrum of SBMA. To our knowledge, this is the first case of SBMA comorbid with myasthenic syndrome limited to the dropped head.