Andersen syndrome is a rare hereditary pathology characterized by a prolonged QT interval and high amplitude U waves on the ECG, ventricular arrhythmias, attacks of muscle paralysis, the presence of external signs of dysmorphogenesis. Patients suffer from low-set ears, wide forehead, abnormally enlarged jaw, persistent deformity of the fingers with adhesions and webbing, increased distance between the eyes, short stature, scoliosis. The diagnosis is made on the basis of clinical findings, genetic findings, and ECG.