Caudal regression in fetus with de novo SMARCA2 pathogenic variant

Nicolaides-Baraitser syndrome (NCBRS) is a rare autosomal dominant genetic condition that is characterized by severe intellectual disability, dysmorphic facial features, short stature, sparse hair, and early onset seizures. This diagnosis is established by suggestive clinical findings and the identification of a heterozygous SMARCA2 pathogenic variant by molecular genetic testing. There are not, however, consensus clinical diagnostic criteria for this condition as there are so few documented cases. Here, we present a case of prenatally diagnosed caudal regression with sacral agenesis and congenital vertical talus (rocker bottom feet) that was ultimately found to have a de novo SMARCA2 pathogenic variant. The patient had an amniocentesis with normal karyotype and microarray followed by failed direct rapid whole exome sequencing (WES) due to maternal cell contamination. She elected for termination of the pregnancy based on the clinical prognosis of the ultrasound findings; WES revealed a pathogenic variant after her termination. We believe this is the first case of these findings associated with NCBRS. If any future cases of either finding are found in association with a SMARCA2 genetic variant, caudal regression and rocker bottom feet should be included in the spectrum of physical traits associated with this pathogenic variant.