Discrete membranous subaortic stenosis in siblings

Genetics of canine subvalvular aortic stenosis (SAS)

Subvalvular aortic stenosis (SAS) is one of the most common congenital heart defects of dogs. The disease is characterized by obstruction of the left ventricular outflow tract, resulting in pressure overload on the left ventricle. The etiology of obstruction is a fibromuscular nodule, ridge, or ring of tissue that increases aortic outflow tract velocity. This review is focused on the prevalence, inheritance pattern, and current genetic insights of canine SAS. The prevalence of this disease was reported at 4.7 % in a large veterinary referral hospital. The mode of inheritance for this disease has also been described in breeds with a high disease prevalence such as the Bullmastiff, Bouvier des Flandres, Dogue de Bordeaux, Golden Retriever, Newfoundland, and Rottweiler. Genetic investigations seeking to identify causative mutations for SAS are lacking with only a single published variant associated with SAS in Newfoundlands.

Genetic evidence of subaortic stenosis in the Newfoundland dog

Subaortic stenosis (SAS) is a cardiac disorder with a narrowing of the descending aorta below the left ventricular outflow tract of the heart. It occurs in several species and breeds. The Newfoundland is one of the dog breeds where it is more common and usually leads to death at early adulthood. It is still discussed to which extent SAS has a genetic background and what its mode of inheritance could be. Extensive pedigree data comprising more than 230,000 Newfoundland dogs from the European and North American population reaching back to the 19th century including 6023 dogs with a SAS diagnosis were analysed for genetic factors influencing SAS affection. The incidence and prevalence of SAS in the analysed Newfoundland population sample were much higher than those reported in previous studies on smaller population samples. Assuming that some SAS-affected dogs remained undiscovered or were not reported, these figures may even be underestimated. SAS-affected Newfoundland dogs were more often inbred and closer related to each other than unaffected dogs, which is an indicator for a genetic background of SAS. The sex had no significant impact on SAS affectedness, pointing at an autosomal inheritance. The only simple mode of inheritance that fitted the data well was autosomal codominant with lethal homozygosity and a penetrance of 1/3 in the heterozygotes.

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.