The Jervell and Lange-Nielsen syndrome (JLNS) comprises profound congenital sensorineural deafness associated with syncopal episodes. These are caused by ventricular arrhythmias secondary to abnormal repolarisation, manifested by a prolonged QT interval on the electrocardiogram. Recently, in families with JLNS, Neyroud et al. reported homozygosity for a single mutation in KVLQT1 , a gene which has previously been shown to be mutated in families with dominantly inherited isolated long QT syndrome [Neyroud et al . (1997) Nature Genet ., 15, 186-189]. We have analysed a group of families with JLNS and shown that the majority are consistent with mutation at this locus: five families of differing ethnic backgrounds were homozygous by descent for markers close to the KVLQT1 gene and a further three families from the same geographical region were shown to be homozygous for a common haplotype and to have the same homozygous mutation of the KVLQT1 gene. However, analysis of a single small consanguineous family excluded linkage to the KVLQT1 gene, establishing genetic heterogeneity in JLNS. The affected children in this family were homozygous by descent for markers on chromosome 21, in a region containing the gene IsK . This codes for a transmembrane protein known to associate with KVLQT1 to form the slow component of the delayed rectifier potassium channel. Sequencing of the affected boys showed a homozygous mutation, demonstrating that mutation in the IsK gene may be a rare cause of JLNS and that an indistinguishable phenotype can arise from mutations in either of the two interacting molecules.
In a population‐based study including 35 218 infants born alive during the 15‐y period 1982–96, 360 (1%) were diagnosed as having a congenital heart defect (CHD). At a follow‐up 3–18 y after birth (median 9.5 y) 154 patients (42.8%) were spontaneously cured; of these, 142 (92.2%) had ventricular septal defects (VSDs). Forty‐two patients (11.7%) died, 22 of these (52.4%) during the neonatal period (0–28 d after birth). A total of 119 patients (33.1%) underwent therapeutic procedures (surgery, catheter interventions), 24 (20.2%) of whom died. Of the 95 children surviving therapeutic procedures, 54 (56.8%) had their defects completely repaired, while 41 (43.2%) had residual defects or cardiac sequelae, often of minor importance. In 69 children (19.2%) with persistent non‐operated defects, 43 (62.3%) had VSDs. A chromosomal disorder, syndrome or associated extracardiac malformation occurred in 72 children (20%). Conclusions: The study underlines the broad variety in severity of CHDs, with a high neonatal mortality rate as well as a high rate of spontaneous cure. It is estimated that 25% of infants born with a CHD will grow into adult age with persistent non‐operated defects, residual defects or cardiac sequelae after therapeutic procedures.
The study underlines the broad variety in severity of CHDs, with a high neonatal mortality rate as well as a high rate of spontaneous cure. It is estimated that 25% of infants born with a CHD will grow into adult age with persistent non-operated defects, residual defects or cardiac sequelae after therapeutic procedures.
In a population-based study of 35,218 infants born alive during the 15 years from 1982 to 1996, 353 (1%) were diagnosed as having a congenital heart defect, of whom 84 (24%) were diagnosed subsequent to discharge from hospital after birth (2.4/1000). Of these, 40 (48%) had a ventricular septal defect, 14 (17%) an atrial septal defect, 9 (11%) a patent arterial duct, 8 (10%) an aortic stenosis and 13 (15%) other defects. Compared with those in whom diagnosis was made before discharge, the group of patients with defects detected late had an increased prevalence of atrial septal defects, patent arterial duct and aortic stenosis, but less decreased prevalence of ventricular septal defects (p< 0.05). Median age at detection of the defects subsequent to discharge was 6 months (range 2 weeks-11 years). Seven patients (8%) presented with clinical symptoms of cardiac decompensation. The mortality rate was significantly lower in those in whom defects were detected late (1/84; 1%) as compared with those detected immediately after birth (37/269; 14%) (p < 0.05). The total rate for early detection was the same after using one clinical examination (8.2/1000) of newborns as our basic routine instead of two (7.1/1000) (p > 0.05). A substantial proportion of congenital cardiac malformations are detected after discharge from hospital after birth. Some patients with these lesions present with cardiac decompensation and are in need of medication and surgery. One clinical examination of newborns detects congenital malformations of the heart as efficient as two.
Jervell and Lange-Nielsen syndrome (JLNS) is an autosomal recessive syndrome characterised by profound congenital sensorineural deafness and prolongation of the QT interval on the electrocardiogram, representing abnormal ventricular repolarisation. In a study of ten British and Norwegian families with JLNS, we have identified all of the mutations in the KCNQ1 gene, including two that are novel. Of the nine mutations identified in this group of 10 families, five are nonsense or frameshift mutations. Truncation of the protein proximal to the recently identified C-terminal assembly domain is expected to preclude assembly of KCNQ1 monomers into tetramers and explains the recessive inheritance of JLNS. However, study of a frameshift mutation, with a dominant effect phenotypically, suggests the presence of another assembly domain nearer to the N-terminus.
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