Asthma as a cause of persistent dyspnea in treated myasthenia gravis patients

The aim of this study was to evaluate the proportion of patients with treated myasthenia gravis (MG) who present with dyspnea not related to MG.

We analyzed the files of 63 consecutive adult patients with treated MG and persistent dyspnea who had been referred to our Pulmonary Function Test (PFT) Department between 2000 and 2010.

We observed that asthma was the first cause of MG-unrelated dyspnea in MG patients, with 9 patients (14%) presenting with asthma-related PFT abnormalities. Six patients had asthma for several years before developing MG, and 3 patients (4%) developed asthma a few months after MG was diagnosed, suggesting a non-coincidental association between the two conditions. In all 3 cases, asthma appeared in elderly patients with severe late-onset AchR-Ab- positive MG, treated with pyridostigmine and corticosteroids and/or intravenous immunoglobulins. In all 3 patients, β(2)-adrenergic agonist treatment allowed only partial control of dyspnea. In one case, respiratory symptoms were alleviated when pyridostigmine dosage was reduced.

Patients with treated MG and persistent dyspnea should be investigated for asthma using PFT before being diagnosed with refractory MG. If asthma is diagnosed, a bronchodilator treatment should be instituted and a reduction in pyridostigmine dosage should be proposed.