Background: Spinal muscular atrophy (SMA) is an autosomal recessive disorder due to degeneration of motor neurons in the anterior horn of the spinal cord and the medulla oblongata, resulting in progressive, symmetrical muscle weakness and atrophy of the proximal limbs and trunk. Patients often die from complications such as lung infections and respiratory failure.
Objective: We summarise the pulmonary function of adult SMA type 2 and 3 patients under gene modification therapy.
Methods: We performed pulmonary function tests on patients at baseline and after 6 months of nusinersen treatment, in which forced vital capacity (FVC), forced expiratory volume at one second (FEV1), FEV1/FVC%, peak expiratory flow (PEF), maximal mid-expiratory flow (MMEF), and diffusion lung capacity for carbon monoxide (DLCO) were measured and analysed. Measurements were expressed as measured values and as a percentage of predicted values.
Results: Based on baseline pulmonary function, patients with SMA were found to have varying degrees of respiratory dysfunction, mainly in the form of restrictive dysfunction with decreased FVC and FEV1, whereas FEV1/FVC% is usually unaffected. Expiratory airflow limitation with reduced PEF is likewise observed, whereas diffusion function is usually unaffected. By analysing the pulmonary function of five SMA patients treated with nusinersen, we found that the mean values of FVC, FEV1, FEV1/FVC%, MMEF, and PEF improved after 6 months compared to baseline, although the changes were not statistically significant.
Conclusion: People with SMA usually demonstrate restrictive impairment while diffusion capacity is generally not impacted. Patients’ pulmonary function saw an improvement after gene modification therapy, though not to a degree that was statistically significant.