Prenatal Diagnosis of KBG Syndrome: Phenotypic and Genotypic Features of 12 Fetal Cases With the Disorder.

Objective: To present prenatal sonographic features, genomic results, and pregnancy outcomes of fetuses with KBG syndrome (KBGS).

Method: This was a retrospective study of 12 cases with KBGS diagnosed by prenatal ultrasound and confirmed by genetic testing. Clinical and laboratory data were collected for these cases, including maternal demographics, prenatal sonographic findings, molecular test results, and pregnancy outcomes.

Results: Twelve cases of KBGS were diagnosed prenatally with confirmatory genetic testing. Five had an abnormal first-trimester ultrasound with increased nuchal translucency (NT). Seven cases had a normal first-trimester ultrasound. Among these, four had mild ventriculomegaly in the second or third trimester, one had an arachnoid cyst found at 22 weeks, one had umbilical-systemic shunt, ventriculomegaly and polyhydramnios found at 24 weeks, and one presented with fetal growth restriction at 30 weeks. Four pregnancies continued to term, and infants presented with the classic phenotype of KBGS at a follow-up of 12 months. All ANKRD11 alterations in the 12 cases were de novo, and were characterized as either deletions encompassing ANKRD11 or loss-of-function variants.

Conclusion: Increased NT and mild ventriculomegaly are two common sonographic features of fetal KBGS. Prenatal diagnosis of KBGS can be achieved with ultrasound and comprehensive molecular testing.