Clinical and molecular studies in two families with Fraser syndrome: a new FRAS1 gene mutation, prenatal ultrasound findings and implications for genetic counselling: Fraser syndrome is a rare autosomal recessive genetic disorder characterized by cryptophthalmus, variable expression of cutaneous syndactyly of fingers and toes, genital ambiguity and renal agenesis/dysgenesis. We present here molecular and clinical findings of four fetuses with FS from two families. Molecular genetic studies in the two families revealed mutations in FRAS1 gene allowing better genetic counselling and subsequent prenatal diagnosis in one of the two families. In family one, a nonsense mutation (c.3730C>T, p.R1244X) previously described in a Polish patient was found. In family two a novel nonsense mutation previously not known was detected (c.370C>T, p.R124X). PGD is planned for family I.