Is prenatal diagnosis possible?
Prenatal diagnosis
Since AGS is, with rare exceptions, inherited as an autosomal recessive trait, most couples with an affected child have a 25% risk of the disease recurring in each future pregnancy. There exist rare cases in which it has been found to be inherited as an autosomal dominant trait (heterozygous TREX1, ADAR1 and IFIH1 mutations); in the majority of cases, these seem to be de novo mutations (except in rare families with mutations in ADAR1 and IFIH1 in which the mutation was transmitted by asymptomatic family members. These are real exceptions, to date found only for these two genes).
Today, genetic tests allow us to obtain a definite diagnosis of AGS in a large proportion of cases: however, it is important to note that diagnostic prenatal testing in at-risk pregnancies is possible only in families that already have an affected child, in whom the disease-causing gene has been identified. If the affected child's mutation is known, then, in the event of a further pregnancy, the DNA of foetal cells obtained by chorionic villus sampling (at 10-12 weeks of gestation) or by amniocentesis (15-18 weeks of gestation) can be examined for the presence of the same mutation.