Prenatal Diagnosis of Proteus Syndrome: About a Case.

Proteus syndrome (PS) is a rare disorder (< 1/1000000), marked by progressive overgrowth commonly impacting the skeleton, skin, adipose tissue, and central nervous system. Clinical criteria were established in 2019. PS arises from a somatic activating variation in the AKT1 gene. We report the second case of PS diagnosed prenatally using whole exome sequencing (WES). A 34-year-old woman was referred for nonvisualized anterior brain structures and genital anomalies. At 21 weeks of gestation (WG), ultrasonography confirmed brain anomalies, genital anomalies, and macrosomia. Array-CGH revealed no pathogenic imbalances (arr(X,1-22)×2). Follow-up ultrasound (25 WG) and MRI (27 WG) also showed a megalencephaly, leading to WES on amniocytes. The reported mosaic variation in AKT1 was identified. Medical termination of pregnancy occurred at 30 + 1 WG. We present a case of PS confirmed prenatally via WES. To date, six cases of prenatal PS suspicion have been reported, four of which lacked molecular diagnosis. Calculating prenatal clinical scores indicate PS could not be definitively diagnosed without molecular confirmation. Certain features, such as limb malformation and gray matter heterotopia, seem to be significant in prenatal diagnosis. WES, with an average coverage depth of 130X, is valuable for diagnosing suspected PS.