Birk-Barel syndrome

Birk-Barel syndrome, also known as Birk-Barel mental retardation dysmorphism syndrome, is a rare genetic disorder caused by mutations in the KCNK9 gene (also known as TASK3), which encodes a two-pore domain potassium channel. This condition follows a unique pattern of inheritance: it is inherited in an autosomal dominant manner but is subject to maternal genomic imprinting, meaning the disease manifests only when the mutation is inherited from the mother. The KCNK9 gene is maternally expressed, so paternal copies are normally silenced. When the maternal copy carries a pathogenic variant, the individual develops the syndrome. The hallmark features of Birk-Barel syndrome include intellectual disability (typically moderate to severe), characteristic facial dysmorphism, and congenital hypotonia. Facial features may include an elongated face, broad nasal tip, a tented or thin upper lip, and a high-arched palate. Affected individuals often present at birth or in the neonatal period with significant feeding difficulties related to hypotonia, which may require specialized nutritional support. Additional features can include joint contractures, particularly of the fingers, and reduced muscle bulk. Some patients may also exhibit behavioral abnormalities and limited or absent speech development. There is currently no specific or curative treatment for Birk-Barel syndrome. Management is supportive and multidisciplinary, focusing on addressing feeding difficulties, optimizing developmental outcomes through early intervention therapies (physical therapy, occupational therapy, and speech therapy), and managing hypotonia. Genetic counseling is important for affected families, particularly given the imprinting mechanism that governs disease expression. The condition was first described in 2008 in a consanguineous Israeli Bedouin family, and the number of reported cases worldwide remains very small.

Common questions about Birk-Barel syndrome