Spinal Muscular Atrophy Results and Comparison of Commonly Used Methods

Aim: We aimed to share our genetic test results for SMA since 2001, and compare the commonly used screening and diagnostic methods for SMA. Materials and Methods: The subjects consist of 222 individuals including SMA cases and their relatives, who referred our center for the investigation of SMA between the years 2001- 2019. The results of Restriction Fragment Length Polymorphism (RFLP) between 2001-2015 years and Multiplex Ligation-dependent Probe Amplification (MLPA) between 2015-2019 years are investigated. RFLP is also used for selected cases after 2015. Results: There is no prominent difference in diagnosis of SMA cases between methods. About 18% of the samples have homozygous SMN1 exon 7-8 deletion. MLPA is better in determining the variants owing to SMN2 gene. Conclusion: There is no evident difference between the methods in the diagnosis of SMA. But, because of its ability in screening heterozygous SMA carriers and superiority in determining the SMN2 copy number, the MLPA is markedly more successful. RFLP is kept as second method for special cases and used when confirmation is needed. In addition to these widely used techniques, there is a need for commonly used tests that able to detect SMN1 point mutations (2-5% of SMA cases) and identify if 2 SMN1 copies which are present on the same chromosome; the situation has a frequency of 3.6% in population.