Mutation in KCNJ2 Gene in a Boy with Atypical Features of Andersen–Tawil Syndrome, ADHD, and ASD: An Expanding Phenotype

Andersen–Tawil syndrome, a potassium ion channelopathy, is caused by mutations in the KCNJ2 gene, and accounts for approximately 10% of channelopathies. Phenotype is variable. An 11-year-old boy presented with periodic paralysis without localizing neurological signs, associated in only two of three occasions with hypokalemia, on a background of a diagnosis of attention deficit hyperactivity disorder and autism spectrum disorder. There was a history of syncope and palpitations. This was a matter of diagnostic uncertainty due to the difficulty in interpreting his neurological signs, and inconsistency of abnormal potassium levels. In children/young people with recurrent episodes of weakness without localizing signs on physical examination, and syncope, the possibility of a channelopathy should be considered, even in the absence of serum electrolyte abnormalities. There is a possible link between KCNJ2 mutations and difficulties in attention and a specific neurocognitive profile.