ABSTRACT
We report two cases of Joubert syndrome initially tentatively diagnosed by prenatal ultrasound in the first or second trimester which were thereafter confirmed by whole exome sequencing (WES). Case 1 was one of the twins who presented with increased intracranial transparency (IT) and thinner brainstem at 12 +1 gestational weeks. Ultrasound at 18 +2 weeks found multiple intracranial malformations, "molar tooth sign (MTS)" at the midbrain-hindbrain junction level in the cerebral cross section, and bilateral ventriculomegaly. Enlarged and echogenic kidneys and oligohydramnios were also detected. In case 2, ultrasound image at 17 +5 weeks of gestation indicated multiple intra-and extra cranial and extracranial malformations, MTS in the midbrain-hindbrain junction plane, bilateral ventriculomegaly, unclear cavum septum pellucidum. Extracranial anomalies were bilateral multicystic enlarged kidneys, invisible bladder, and oligohydramnios. Both fetuses underwent amniocentesis, which showed normal karyotype and no copy number variation was detected. However, variation of the TMEM67 gene (c.312+5G>A at introns 2 and c.1175C>G at exon12) was detected in both fetuses by WES, supporting the diagnosis of Joubert syndrome. Selective reduction and termination of pregnancy were performed on case 1 and case 2 at 18 +5 and 19 weeks of gestation, respectively.