Summary

Andersen's syndrome (AS) is a rare disorder characterized by periodic muscle paralysis, prolongation of the QT interval with a variety of ventricular arrhythmias (leading to predisposition to sudden cardiac death) and characteristic physical features: short stature, scoliosis, low-set ears, hypertelorism, broad nasal root, micrognathia, clinodactyly, brachydactyly and syndactyly. AS is inherited as an autosomal dominant trait although sporadic cases have been reported. Penetrance is extremely variable. Mutations in KCNJ2, which encodes the alpha subunit of the potassium channel Kir2.1, account for approximately 60% of cases. Treatment depends on the individual and their reaction to potassium. Patients with severe arrhythmias may require a pacemaker.