Incidence of Spinal Muscular Atrophy in Poland – More Frequent than Predicted?

<i>Background:</i> The application of molecular methods has enhanced and enlarged the diagnostics of spinal muscular atrophy (SMA) and its carriership. It allows for reliable epidemiological studies which are of importance to demography and genetic counseling. <i>Methods:</i> This study sought to evaluate the incidence of SMA in Poland, on the basis of the prevalence of the <i>SMN1</i> gene deletion carrier state in the general population, as well as an analysis of all cases of SMA diagnosed in the years 1998–2005. <i>Results:</i> The prevalence of the <i>SMN1</i> gene deletion carrier state was estimated at 1 per 35 persons (17/600), yielding an incidence of SMA equal to 1 per 4,900. By contrast, the incidence of SMA based on the results of the meta-analysis was an estimated 1 per 7,127 in Warsaw and 1 per 9,320 persons across Poland, suggesting that some cases of SMA remain undiagnosed. SMA1 predominated among the diagnoses, accounting for 69% of all cases. <i>Conclusion:</i> A high prevalence of the <i>SMN1</i> deletion carrier state in the general population indicates that SMA could be a more frequent disease than is predicted by the epidemiological data regarding diagnosed cases.