Dyspnoea due to vocal fold abduction paresis in anti-MuSK myasthenia gravis

Case report

A 24-year-old female student who had inspiratory stridor and exertional dyspnoea for 2 years was seen in our neurology and otolaryngology outpatient department. The dyspnoea disabled her in walking stairs and stridor occurred after physical exercise, such as walking stairs or talking. In addition, in the past 2 years, she had suffered from recurrent episodes of diplopia, which intensified in the evening; this had been diagnosed as decompensated oesotropia. She also complained of difficulty in swallowing, but had no problems chewing. On physical examination, rhinolalia aperta, right-sided ptosis, weakness of neck flexors and a myopathic face were found. She was submitted to respiratory function tests. Her spirometry showed no decrease in vital capacity (110%). A flow volume loop (FVL) after physical exercise showed an inspiratory plateau, indicating an inspiratory airway obstruction. On laryngoscopy, a bilateral abduction paresis of the vocal folds was seen with a maximum abduction angle of 15 degrees (normally 30–70 degrees) …