FREM2-related Fraser syndrome with popliteal pterygium and structural central nervous system anomalies

Fraser syndrome (FS) is a rare multiple malformation disorder characterized by cryptophthalmos, characteristic craniofacial dysmorphism, cutaneous syndactyly, malformations of the respiratory and urinary tract, and anogenital anomalies. Although the characteristic presentation of FS can be detected prenatally, oligohydramnios often challenges the clinical diagnosis. Here we report on the atypical prenatal and postmortem findings of a fetus with FS caused by a novel homozygous frameshift variant in FREM2. Our study highlights the variable manifestations of the FS and expands the clinical spectrum to include popliteal pterygium and structural central nervous system anomalies.