KCNK9 and Birk-Barel syndrome: In a single report, familial Birk Barel syndrome that is characterized by mental retardation, hypotonia, and facial and skeletal dysmorphism is caused by a mutation in the paternally imprinted potassium channel TASK-3 (KCNK9) on chromosome 8q24.3 (Barel et al, 2008).