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Autosomal dominant
In autosomal dominantly inherited conditions the trait is demonstrated in heterozygotes i.e. individuals with one normal allele and one mutated allele will be affected. It is often possible to trace the disorder through many generations of the family. The offspring of an individual with an autosomally dominant condition has a 1 in 2 (50%) chance of being affected. The features of an autosomal dominant condition can vary between members of the same family (variable expressivity). It can appear that some members are unaffected despite having the abnormal allele and the condition can appear to skip a generation (reduced penetrance).
Many autosomal conditions appear to arise de novo due to a new mutation, for example thanantophoric dwarfism which arises from a mutation in the fibroblast growth factor receptor 3 (FGFR3) gene. New mutations can be suspected in the absence of a positive family history. It is possible that one of the parents of a child with an apparent new dominant mutation has gonadal mosaicism accounting for the rare finding of apparently unaffected parents having two affected children.
Some Autosomal Dominant Conditions
Achondroplasia |
Adult polycystic kidney disease |
Ehlers-Danlos Syndrome |
Familial Adenomatous Polyposis coli |
Familial hypercholestrolaemia |
Gilbert’s syndrome |
Huntingdon’s chorea |
Von Hippel-Lindau disease |
Marfan’s syndrome |
Myotonic dystrophy |
Neurofibromatosis types 1 and 2 |
Tuberose sclerosis |
Von Willebrand’s disease |
Autosomal Dominant Family Tree
The key features supporting autosomal dominant inheritance are that the condition affects every generation with male to female and female to male inheritance. Autosomal dominant conditions affect both sexes equally and there can be transmission between the sexes in every combination i.e. male to male, male to female, female to male and female to female.
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