B9D2-related disorders are ultra-rare monogenic conditions, characterized by multiple congenital anomalies affecting the brain, kidneys, and limbs. Key clinical features include neural tube defects or the presence of a molar tooth sign on brain imaging, polydactyly, and renal and/or hepatic cysts.
These disorders are caused by biallelic variants in the B9D2 gene.
To date, only four families have been reported with B9D2-related disorders—two with Meckel syndrome and two with Joubert syndrome.
B9D2