A 52-year-old woman had a 14-year history of
stridor attacks. Pulmonary function tests revealed reversible
airway obstruction, and
bronchial asthma was diagnosed. She also has bilateral ptosis,
diplopia, and moderate weakness of all four limbs; a positive
edrophonium test confirmed the diagnosis of
myasthenia gravis. Although the parasympathetic system plays an important role in the regulation of bronchial tone, in this patient the
edrophonium test did not provoke an asthmatic attack or exacerbate pulmonary function, except for increases in sputum production and in frequency of
cough. The general weakness was usually worse in the afternoon. The decrease in grip strength and the shortening of arm elevation time also occurred after
asthma attacks, which means that general muscle fatigue was caused by the work of breathing. Furthermore,
dyspnea increased and pulmonary function worsened when an
anti-cholinesterase inhibitor was discontinued, probably because of respiratory muscle weakness. Accordingly, the clinical status of
bronchial asthma seemed to change in parallel with that of the
myasthenia gravis.