Respiratory function dynamics in a patient with refractory AChR-seropositive myasthenia gravis under eculizumab treatment: A case report

Myasthenia gravis (MG) is an autoimmune disease characterized by the formation of antibodies to the postsynaptic membrane of the neuromuscular junction in voluntary muscles. Among all manifestations of MG, the most severe is respiratory dysfunction, which results from the weakness of the diaphragm, intercostal and accessory muscles, as well as pharyngeal and laryngeal muscles. An analysis of respiratory disorders was conducted in a 29-year-old female patient suffering from highly active, refractory, generalized MG with juvenile onset and anti-acetylcholine receptor antibodies. Parameters of spirometry, impulse oscillometry, lung diffusion capacity (DLCO), and respiratory muscle strength were studied. Significant impairment of respiratory muscle strength was revealed, along with signs of bronchial asthma with predominant small airway involvement, which is likely an autoimmune comorbid condition and represents a non-eosinophilic endotype of airway inflammation. The patient began receiving targeted immunological therapy for myasthenia with monoclonal antibodies against the C5 complement component. After the initiation of therapy, a dynamic functional assessment of the respiratory system was conducted, revealing an improvement in respiratory function based on parameters such as vital capacity, forced vital capacity and forced expiratory volume in one second, and DLCO, which highlights the role of complement inhibitors in treating neuromuscular dysfunction. However, parameters of inspiratory and expiratory muscle strength (maximal inspiratory and expiratory pressures, MIP and MEP) did not change. Pulmonary function testing is essential for clarifying the state of the respiratory system and muscle strength, ruling out concomitant lung and bronchial pathology, while dynamic assessment of respiratory parameters allows for objective evaluation of the efficacy of targeted therapy.

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