Joubert syndrome 9 is a multisystem disorder characterized by brain anomalies such as cerebellar vermis hypoplasia/aplasia, thickened and reoriented superior cerebellar peduncles, and an abnormally large interpeduncular fossa. These findings give the appearance of a molar tooth sign on a brain MRI. Symptoms of JBTS9 may include neurological problems such as intellectual disability, seizures and ventriculomegaly, ophthalmological anomalies such as retinitis pigmentosa, astigmatism, nystagmus and cataract as well as renal and hepatic abnormalities such as nephronophthisis and hepatosplenomegaly.
This congenital syndrome affects infants and it is usually diagnosed right after birth. It has a prevalence of 1/80,000 to 1/100,000 live births. The disorder does not appear to have a gender or racial bias. Treatment of Joubert syndrome depends on the severity of symptoms. It is focused mainly on physical, occupational and speech therapy as well as infant stimulation. JBTS9 patients may also require cataract surgery and low-vision aids.
Al-Hamed et al. (2016) attempted to identify causal gene mutations in a cohort of 44 Saudi families affected by antenatal cystic kidney disease. In one case, antenatal ultrasound examination found cystic kidneys, cerebellar vermis aplasia, dilated cisterna magna and corpus callosum agenesis. The subject was found to be homozygous for the known CC2D2A mutation c.3364C>T (p.P11225). In another case, ultrasound findings included cystic kidneys, cerebellar vermis aplasia and dilated cisterna magna. While fetal DNA was unavailable for analysis, both parents were found to be heterozygous for the known CC2D2A mutation c.3084delG (p.R1028Rfs*3). The cases were indicative of Joubert syndrome 9 and both resulted in fetal death.