Chromosome 22q11 monosomy and the genetic basis of congenital heart disease

Frequency of 22q11.2 microdeletion in sporadic non-syndromic tetralogy of Fallot cases

BACKGROUND

Tetralogy of Fallot (TOF) is a congenital conotruncal heart defect commonly found in DiGeorge (DGS) and velocardiofacial (VCFS) syndromes. The deletion of chromosome 22q11 has also been demonstrated in sporadic or familial cases of TOF. The aim of the present study was to investigate the frequency of del22q11 in patients with non-syndromic TOF seen at a tertiary Pediatric Cardiology care center.

METHOD

One hundred and twenty three non-syndromic TOF patients were selected and evaluated by history, physical examination and review of medical records. Venous blood was drawn for genomic DNA extraction after informed consent 22q11 microdeletion diagnosis was conducted through a standardized SNP genotyping assay and consecutive homozygosity mapping. Phenotype-genotype correlations regarding cardiac anatomy were conducted.

RESULTS

We evaluated 123 non-syndromic TOF patients for a 22q11 deletion. 105 (85.4%) patients presented pulmonary stenosis and 18 (14.6%) had pulmonary atresia. Eight patients (6.5%) were found to have a deletion. Of the deleted patients, three (37.5%) presented pulmonary atresia. We have verified a tendency towards a higher prevalence of pulmonary atresia when comparing TOF patients with and without 22q11 microdeletion.

CONCLUSIONS

22q11.2 deletion in non-syndromic TOF patients is present in approximately 6% of patients. We suggest a tendency towards a higher prevalence of pulmonary atresia in non-syndromic TOF patients with 22q11 microdeletion. Molecular genetic screening of non-syndromic TOF patient may be important for the correct care of these patients and a more specific genetic diagnostic and counseling.

Approach to congenital heart disease in the neonate

Congenital heart disease in the newborn is a unique and complex problem faced by both pediatricians and cardiologists as it requires skillful handling and balancing of both neonatal issues as well as cardiac physiology. Babies with cyanotic and acyanotic heart disease are physiologically different from each other and management has to be tailored to the individual diagnosis and clinical status. Rapid diagnosis and appropriate management is the key to reducing mortality and morbidity in this fragile patient population. The following review deals with the common presentations of heart problems in a newborn baby and methods of diagnosis, investigative modalities, recent advances and approach to management.

Radiographic evaluation of the neonate with congenital heart disease

Remarkable advances in pediatric cardiology have been spurred by the explosion of technologies both in interventional and surgical techniques and the ability to manipulate the genome of experimental animals. After a brief discussion concerning the striking advances in the molecular understanding of congenital heart disease, this article focuses on clues to the diagnosis of congenital heart disease and on chest radiography and common, specific lesions of the neonate such as hypoplastic left heart, transposition of the great vessels, and severe tetralogy of Fallot. The impact of treatment protocols involving interventional cardiology in the neonate also are discussed.

Mitochondrial trifunctional protein deficiency associated with recurrent myoglobinuria in adolescence

A 23-year-old man with recurrent myoglobinuria had low muscle-free carnitine levels and deficient fasting ketogenesis. Urinary organic acid analysis showed large amounts of C6-C14 3-hydroxydicarboxylic acids. Mitochondrial trifunctional protein (TP), harboring long-chain enoyl-coenzyme A (CoA) hydratase, long-chain 3-hydroxyacyl-CoA dehydrogenase, and long-chain 3-ketoacyl-CoA thiolase showed markedly decreased activity in fibroblasts. On immunoblot analysis, the TP content of his fibroblasts was less than 2% that of the control cells. TP deficiency can be a life-threatening disorder with early infantile onset, but it can also present in adolescence with recurrent myoglobinuria.

The genetic basis of pediatric cardiovascular disease

Congenital heart disease (CHD), cardiomyopathy, and vasculopathies are common causes of mortality and morbidity in pediatrics, including the perinatal period. This article reviews evidence that single gene defects cause many of the pediatric heart diseases. Vasculopathies discussed include Marfan's syndrome, supravalvar aortic stenosis and Williams' syndrome, Alagille's syndrome, and hereditary telangiectasia, the Osler-Weber-Rendu syndrome. Genetic causes of hypertrophic cardiomyopathy caused by sarcomeric protein mutations (beta-cardiac myosin heavy chain) and of dilated cardiomyopathy secondary to structural protein deficiencies (dystrophin) are presented. Defects in proteins essential for myocardial energy production such as oxidative phosphorylation proteins and fatty acid oxidation genes that cause cardiomyopathy or sudden death are described. Gene ablation models in mice, such as RXR alpha and homeobox gene knockouts, which result in cardiac phenotypes resembling human congenital heart disease, are described. Familial types of human CHD which are being investigated for genetic causes by positional cloning methods and known cytogenetic causes of CHD, including the CATCH-22 syndrome and monosomy at 22q11, are presented. General lessons and principles derived from these new and exciting discoveries in human cardiovascular development are surmised.