Congenital myopathies are a heterogeneous group of rare, inherited muscle diseases that typically announce themselves in infancy or childhood through progressive muscle weakness. The genetic defects behind these conditions disrupt the fundamental machinery of the muscle fiber, affecting structures such as the contractile apparatus itself, the systems that handle calcium within muscle cells, and the mitochondria that supply the energy muscle contraction demands. The resulting weakness can compromise the ability to walk, to rise from the floor, and to use the arms and hands for everyday tasks, and in the most severe cases it extends to the respiratory muscles, threatening breathing itself. Because the underlying genetic faults cannot currently be repaired, clinical care has been confined to symptom management: physical therapy, orthopedic interventions, respiratory support, and vigilance against complications. There has been no drug that meaningfully changes what these children can do with their bodies day to day.

The new study, led by researchers at the University of Gothenburg together with clinicians at the Queen Silvia Children’s Hospital, set out to test whether salbutamol, known in some countries as albuterol, could change that picture. Salbutamol is a beta-2 adrenergic agonist, a molecule that stimulates beta-2 receptors and has been inhaled by asthma patients for decades because it rapidly relaxes the smooth muscle of the airways. But when the same compound is taken orally rather than inhaled, it reaches the bloodstream in concentrations that allow it to act on skeletal muscle as well. Beta-2 receptors on muscle fibers participate in signaling pathways that influence protein turnover, and experimental work has shown that beta-2 agonists can stimulate the synthesis of muscle protein, tilting the balance between muscle building and muscle breakdown toward growth. This anabolic side effect is precisely why the drug attracted the attention of neuromuscular researchers interested in conditions defined by weakness rather than by airway disease.

The trial, known as COMPIS, enrolled 18 individuals aged 6 to 16, every one of whom had a congenital myopathy confirmed by genetic testing. The design was a randomized, open-label, blinded-endpoint crossover study, a format well suited to rare diseases where patient numbers are inevitably small. Half the participants began with 24 weeks of oral salbutamol added to their usual care, while the other half continued with usual care alone; after that period, the groups switched. Because each child served as their own control, the comparison between treatment and no treatment could be made within the same individual, reducing the noise that genetic heterogeneity and differing disease severity would otherwise introduce. Assessors scoring the outcomes remained blinded to which treatment period the measurements came from, protecting the results from observer bias even though participants and clinicians necessarily knew what drug was being taken.

The primary outcome was motor function measured with the MFM-32, a standardized rating scale developed specifically for neuromuscular diseases that evaluates what patients can actually do, from standing and transferring to handling objects. After the salbutamol periods, motor function scores were on average 3.61 points higher than after the standard-care periods. In the world of neuromuscular medicine, where meaningful change on such scales is often measured in single digits over years, a difference of that magnitude achieved in half a year is regarded as a clear and clinically relevant improvement. Muscle strength told the same story. Grip strength in the dominant hand increased by the equivalent of roughly 1.5 kilograms during salbutamol treatment compared with standard care alone, and although increases in other tested muscle groups did not reach statistical significance, the direction of change was consistently favorable.

Perhaps the most striking results came from the functional tests performed by the eleven participants who were able to walk. In the six-minute walk test, a standard measure of endurance and mobility in neuromuscular research, the children covered an average of 435 meters before the trial. During salbutamol treatment, that distance rose to 473 meters, an additional 38 meters of walking that represents real, visible gains in stamina for children whose energy reserves are severely limited. For context, children of similar age with typical muscle function walk about 600 meters in six minutes, so the drug moved these patients meaningfully closer to normal performance. The researchers also timed how quickly the ambulatory children could rise from the floor to a standing position, a classic test of proximal muscle power. Before treatment, the task took an average of 8.29 seconds; with salbutamol, it took 6.39 seconds. A child with normal strength completes the same movement in one to two seconds, which illustrates both how impaired these children were and how much ground the medication helped them recover.

The benefits extended beyond the limbs. Forced vital capacity, the volume of air a person can exhale after taking the deepest possible breath, was on average approximately 0.2 liters higher during salbutamol treatment than during standard care. In congenital myopathies, weakening of the respiratory muscles is one of the most feared aspects of the disease, driving recurrent chest infections, sleep-disordered breathing, and eventually the need for ventilatory support. A measurable improvement in respiratory muscle performance, even a modest one, therefore carries potential importance well beyond the numbers themselves. The treatment was well tolerated throughout the study, and no serious side effects were reported, an encouraging safety profile for a drug whose tolerability in children is already extensively characterized from decades of asthma use.

For the families involved, the significance of the trial is captured less by rating scales than by daily life. Eva Michael, a doctoral student in pediatric neurology at the University of Gothenburg and a specialist physician at the Queen Silvia Children’s Hospital, described the change she observed in the children’s everyday functioning. Simply the fact that they had more energy, she noted, that they could manage a full day at school followed by activities and homework without becoming completely exhausted and bursting into tears, is very important for these children. That framing underscores a point that clinical trials in rare diseases often struggle to convey: for a child who cannot sustain a normal day, an incremental gain in endurance can translate into participation in school, friendships, and family life that would otherwise be out of reach.

The researchers themselves are careful about what the study can and cannot establish. With 18 participants at a single center in Sweden, the trial is small, and congenital myopathies encompass many distinct genetic subtypes that may respond differently to a beta-2 agonist. The open-label design, with blinded endpoint assessment, cannot fully exclude expectation effects on the part of participants and families. Michael and her colleagues emphasize that the findings need to be confirmed in larger international studies involving longer treatment periods and follow-up before any change to clinical practice. Even so, the results suggest that oral salbutamol could potentially become a symptom-relieving treatment option for children and adolescents with congenital myopathies in the future, pending the development of other drugs that might address the diseases more fundamentally.

If those larger trials succeed, the implications would extend well beyond this single rare disease community. Salbutamol is cheap, globally available, and already approved for pediatric use, meaning that a positive confirmation could translate into treatment access far faster than a newly developed molecule ever could. The trial also adds to a growing body of evidence that repurposing established drugs can open doors in neuromuscular medicine, where the small patient populations of individual genetic disorders rarely justify the cost of developing therapies from scratch. For now, the COMPIS results stand as a carefully controlled demonstration that a familiar asthma inhaler medication, taken by mouth, can give children with congenital myopathies something they have never had before: a medicine that measurably strengthens the muscles they rely on to stand, to walk, and simply to get through their day.

Subject of Research: Oral salbutamol treatment for motor function and muscle strength in children with congenital myopathies

Article Title: Asthma medication improved motor skills and strength in children with muscle disease

Article References: Asthma medication improved motor skills and strength in children with muscle disease. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: salbutamol, congenital myopathies, neuromuscular disease, randomized crossover trial, muscle strength, motor function, pediatric neurology, six-minute walk test, forced vital capacity, drug repurposing, University of Gothenburg, EClinicalMedicine