Prenatal diagnosis of a fetus with Proteus syndrome

What's already known about the topic? Proteus syndrome is a rare condition characterized by mosaic overgrowth of tissue types derived from all 3 germ layers. It has a highly variable presentation and is generally diagnosed by clinical criteria after birth. What does this study add? This case describes the ultrasound and autopsy findings of a rare presentation of a fetus with AKT1‐related Proteus syndrome. It demonstrates many systemic and neurologic findings of Proteus syndrome in a fetus that have not been reported in the literature. Prenatal diagnosis of mutant AKT1‐related Proteus syndrome by antenatal ultrasound is possible and may present without obvious segmentation in a severe phenotype.