Birk Barel syndrome also known as KCNK9 imprinting syndrome is a rare developmental disorder associated with a loss-of-function variant in KCNK9, an imprinted gene with maternal expression on the 8th chromosome encoding the TASK3 (TWIK-related acidity inhibited K + -channel 3). Only two variants of KCNK9 have been associated with this condition before, both of them leading to the same amino-acid exchange p.Gly236Arg (Barel, 2008, Graham, 2016). We describe a case of a 17-year-old girl presenting with very similar phenotype and pure motor neuropathy with a novel variant c.710C > A: p.Ala237Asp (NM_001282534.1) in KCNK9 found by whole exome sequencing. Our case suggests that Birk Barel syndrome may not be caused only by variants leading to amino-acid exchange p.Gly236Arg but also by other missense variant in this gene and that peripheral motor neuropathy might be a feature of this syndrome.

Department of Paediatric Neurology 2nd Faculty of Medicine Charles University Prague and Motol University Hospital Czech Republic

Department of Pathology and Molecular Medicine 2nd Faculty of Medicine Charles University Prague and Motol University Hospital Czech Republic

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