Changes of Motor Function Tests in Congenital Myopathy Subjects Treated With Oral Salbutamol as Compared to no Treatment

Congenital myopathies (CM) is a large group of muscle disorders, presenting with hypotonia and non-progressive generalised muscle weakness, which can lead to motor developmental delay.More than 20 genes can cause CM and currently there is no curative treatment for this disorder. Case reports and a smaller study have previous reported that oral salbutamol has benefited subjects with different types of congenital myopathies by increasing their muscle strength.The exact effect of salbutamol in muscle cells isn't exactly known but it has been hypothesized to have an anabolic effect by triggering different pathways inside the muscle cells which increase cell proliferation, decrease apoptosis, decreases proteolysis and increases protein synthesis. The aim of our study is evaluate if daily oral salbutamol can increase the muscle function and muscle strength in these patients after 6 months on treatment, compared to no treatment.

We hypothesise that congenital myopathy subjects treated with daily oral salbutamol will increase in their motor function measure 32 test (MFM32) with at least 3 points after 6 months of treatment as compared to no treatment. We have calculated that a sample size of 18 subjects is needed for this study. Congenital myopathy subjects will be recruited from the whole of Sweden and the study will be performed at the Sahlgrenska university hospital in Gothenburg Sweden. The subjects must have clinical symptoms consistent with congenital myopathy and have a verified mutation in a gene known to cause congenital myopathy. After a screening period of 6 months the eligible subjects will be randomised into two groups, group A and group B . During period 1, group A will receive oral salbutamol 3 times daily and the group B will have no treatment.They will be evaluated after 6 months. Then after a washout period of 1 month, Period 2 will begin where the groups will cross-over, i.e group A will have no treatment and group B will receive oral salbutamol 3 times daily. In total each subject will be evaluated 5 times during 19 months with the same battery of muscle function and strength tests performed each time.