Jervell Lange-Nielsen syndrome (JLNS) is a recessive disorder with congenital 
deafness and long-QT syndrome (LQTS 1). Mutations in the potassium-channel gene 
KVLQT1 (LQTS 1) have been identified in JLNS and in autosomal-dominant LQTS as 
well. We performed haplotype analysis with microsatellite markers in a Lebanese 
family with JLNS, but failed to detect linkage at LQTS 1. Moreover, using this 
approach, we excluded two other ion-channel genes involved in autosomal-dominant 
LQTS, HERG (LQTS 2) and SCN5A (LQTS 3). Our findings indicate that JLNS is 
genetically heterogeneous and that, in this family, an unknown LQTS gene causes 
the disease.