Muscle weakness, palpitations and a small chin: the Andersen-Tawil syndrome.

'Ion channelopathies' have emerged in the past decade as a new cause of several neurological diseases. These Mendelian disorders are caused by mutations in genes that encode ion channel subunits and are often characterised by paroxysmal attacks of brain or muscle dysfunction, interspersed with periods of clinical normality. Andersen-Tawil syndrome is one of the rarest and is characterised clinically by the triad of periodic paralysis, cardiac dysrhythmias and skeletal abnormalities. Mutations in a potassium channel gene, KCNJ2 which encodes the potassium channel, Kir2.1, underlie the disorder. Here, the authors describe a patient and review the clinical spectrum and genetic features of the disorder.