22 January 2009
Last month the American College of Medical Genetics (ACMG) announced that genetic carrier screening for the inherited condition spinal muscular atrophy (SMA) should be made available to all US couples. The most common and severest form of this autosomal recessive genetic disease, SMA type 1, is caused by mutations in the SMN1 gene (see previous news); it causes progressive neurodegeneration and paralysis, with death by the age of two.
SMA affects as many as 1 in 6,000 newborns in the US (see Families of SMA website), and the population carrier frequency for disease-associated SMN1 mutations is estimated to be as high as one in 40. Previously, carrier testing has only been made available to couples with a family history of the disorder, but new guidance from the Professional Practice and Guidelines Committee of the ACMG says this should be extended because the disease meets established criteria for population-based genetic screening. Statement author Dr Thomas Prior said: "Because SMA is a common genetic disorder in all populations, carrier testing should be offered to all couples regardless of race or ethnicity" (see press release).
Pre-conceptual or prenatal carrier screening of couples cystic fibrosis (CF) is already available in the US, although for both CF and SMA, only the most common mutations would be detected by the corresponding genetic tests, and hence most (but not all) carriers would be detected through screening.