Genetics of spinal muscular atrophy

Spinal muscular atrophy (SMA) is a severe genetic disorder. The most frequent form of SMA is inherited in an autosomal recessive mode, caused by a homozygous deletion of a part of the SMN1 gene on the long arm of chromosome 5. Having frequency of carriers in Caucasian population about 1 :40, it is the second most common autosomal recessive disease of childhood. The causal SMN1 gene was found in 1995. Since then, investigation of the number of copies of this gene has been performed by different techniques, the gold standard now being a multiplex ligation-dependent probe amplification. To predict the development of the disease, it is crucial to determine the number of SMN2 gene (so called pseudogene) copies, too.The patient's phenotype is also impacted by other modification factors. Clinical genetics offers counselling to the families and, in relevant cases, recommends carrier testing. With the arrival of treatment possibilities in early stages of the disease, the prompt and early diagnostics has become essential.