affected will die before the age of 15. However, treatment with beta blockers markedly reduces the risk of death, as does, in selected cases, implantation of a defibrillator. Epidemiology Jervell and Lange-Nielsen syndrome affects an estimated one in 166,000 to 625,000 children, and is responsible for less than 10% of all cases of long QT syndrome. It has a markedly higher incidence in Norway and Sweden at up to one per 200,000. References External links This article incorporates public domain text from The U.S. National Library of Medicine GeneReview/NIH/UW entry on Jervell and Lange-Nielsen Syndrome Cardiac arrhythmia Autosomal recessive disorders Rare syndromes Syndromes affecting the heart Syndromes affecting hearing