Prenatal Sonographic and Molecular Genetic Diagnosis of Popliteal Pterygium Syndrome.

Popliteal pterygium syndrome (PPS) is an extremely rare autosomal dominant disorder, characterized by the cleft palate with or without cleft lip, limbs abnormalities with highly characteristic features of popliteal webbing, syndactyly, and genital abnormalities and nail anomalies. Prenatal diagnosis of PPS has been extremely rare. We describe a unique case of fetal PPS at 20 weeks of gestation. The diagnosis of PPS was based on the ultrasound findings of bilateral popliteal webbings, extending from posterior aspects of the upper thighs through the lower legs, resulting in restriction in knee extension, bilateral equinovarus feet with syndactyly, ambiguous genitalia and the grooved lip. Anatomical structures were otherwise normal. Trio whole-exome sequencing revealed a de novo heterozygous IRF6 gene mutation in the fetus, confirming the diagnosis with PPS. In conclusion, popliteal webbing or combination of facial cleft or cleft variants and bilateral abnormal postures of the lower limbs is suggestive of PPS and genetic diagnosis should be warranted.