Autosomal dominant inheritance is characterised by the disease being expressed in the heterozygote and the homozygote. On average, the trait is only inherited in 50% of offspring, there being an equal frequency and severity in each sex for a given condition. There is often a varible expression in the time of onset of autosomal dominant conditions.
At different ends of a spectrum, an autosomal dominant gene may not manifest in any way clinically - non-penetrance - or, it may totally preclude reproduction, as for example, in Apert's syndrome.
Autosomal dominant traits generally tend to be less severe than autosomal recessive traits. In those autosomal dominant traits appropriately investigated, there tends to be defects of structural, carrier or receptor proteins. In addition, stuctural skeletal problems appear are frequently autosomal dominant.
There are approximately 2200 known autosomal dominant traits, the most common being:
disorder frequency / 1000 births
- dominant otosclerosis 3
- familial hypercholesterolaemia 2
- adult polycystic kidney disease 1
- multiple exostoses 0.5
- Huntington's disease 0.5
- neurofibromatosis 0.4
- myotonic dystrophy 0.2
- congenital spherocytosis 0.2
- polyposis coli 0.1
- dominant blindness 0.1
- dominant congenital deafness 0.1