Myasthenia gravis, respiratory function, and respiratory tract disease

Abstract

Myasthenia gravis (MG) is characterized by muscle weakness caused by autoantibodies that bind to the postsynaptic membrane at the neuromuscular junction and impair acetylcholine receptor function. Weakness of respiratory muscles represents the most severe MG manifestation, and 10–15% of all patients experience an MG crisis with the need of mechanical ventilatory support at least once in their life. MG patients with respiratory muscle weakness need active immunosuppressive drug treatment long term, and they need regular specialist follow-up. Comorbidities affecting respiratory function need attention and optimal treatment. Respiratory tract infections can lead to MG exacerbations and precipitate an MG crisis. Intravenous immunoglobulin and plasma exchange are the core treatments for severe MG exacerbations. High-dose corticosteroids, complement inhibitors, and FcRn blockers represent fast-acting treatments that are effective in most MG patients. Neonatal myasthenia is a transient condition with muscle weakness in the newborn caused by mother’s muscle antibodies. In rare cases, treatment of respiratory muscle weakness in the baby is required.

Correlation between Cardiovascular Autonomic and Pulmonary Ventilation Functions in Myasthenia Gravis Patients

“…A large prospective study with 25,639 participants demonstrated that participants with poorer lung function (lower FEV 1 ) are at greater risk of total and cardiovascular mortality, even in the absence of cardiovascular disease [21]. This appears to be particularly important in elderly MG patients, who may experience a high total cardiopulmonary load [3]. In our study, a lower HRV (HF, PSD) was negatively associated with peak inspiratory flow parameters, potentially resulting in inspiratory flow limitations, increased inspiratory effort due to high intrathoracic pressure, and a higher amount of work required for breathing [3,14].…”

“…This appears to be particularly important in elderly MG patients, who may experience a high total cardiopulmonary load [3]. In our study, a lower HRV (HF, PSD) was negatively associated with peak inspiratory flow parameters, potentially resulting in inspiratory flow limitations, increased inspiratory effort due to high intrathoracic pressure, and a higher amount of work required for breathing [3,14]. Previous studies suggest an inverse relationship between lung hyperinflation and cardiac function, which includes the cardiac preload, BRS, and HRV.…”

“…The most serious complication of MG is respiratory dysfunction, which affects approximately 30-40% of adults throughout the course of the disease. In addition, myasthenic crisis and respiratory comorbidities are associated with an increased mortality rate in MG [3,4]. Ventilatory muscle weakness significantly contributes to respiratory muscle involvement in MG patients, who have reduced spirometric values as measured via the forced expiratory volume in the first second (FEV 1 ) and forced vital capacity (FVC) [5,6].…”

“…It has been reported that even well-regulated patients may exhibit ventilatory impairments defined by mild restrictive or mixed restrictive/obstructive patterns [8,9]. In addition, about 11-21% of patients with MG may develop chronic pulmonary diseases, including asthma [3]. Although the etiology of MG remains unknown, it has been determined that inflammation and the modulation of the immune response by cytokines play a role [10,11].…”