How is myotonic dystrophy inherited?

This condition follows a 'dominant' inheritance pattern, which means that on average half of the children of an affected person are themselves affected. Both men and women are equally likely to be affected and to pass on the disorder, but affected women are more likely to have a severely affected child. In general (though not always) the disorder tends to be more severe in successive generations.

Autosomal "dominant" traits
For these traits only ONE copy of the mutated allele is needed for an individual to be affected, and this can be inherited from either parent. Indviduals with a dominant trait have a 1 in 2 chance of passing that allele, and therefore that trait, on to each of their children. Examples of conditions that are inherited as autosomal dominant traits include Huntington disease, myotonic dystrophy and achondroplasia (a form of dwarfism).

In this example (Fig. A), a Mother with an autosomal dominant disorder has two affected children and two unaffected children.

Fig. A

In this example (Fig. B), a Father with an autosomal dominant disorder has two affected children and two unaffected children.

Fig. B

Most healthy adult relatives will not be likely to develop or pass on the disorder, but a careful assessment by an expert is important as mild features can easily be missed. Genetic testing on a blood sample for such relatives can now provide greater certainty, but should always be done with full information as part of genetic counselling. Genetic testing of healthy young children is not recommended.

Very few cases of myotonic dystrophy occur 'out of the blue'. Almost always, one parent proves to be affected, often very mildly. Some parents (or grandparents) prove to carry a very slight genetic change that will never give them symptoms. Careful study of the whole family often shows more members to be affected than would appear likely at first.

Reference, Professor Peter S Harper, University of Wales College of Medicine, Cardiff for the Muscular Dystrophy Campaign

Reference, National Library of Medicine (NLM)

Reference, Murdoch Childrens Research Institute and the Gene Technology Access Centre

Image (Fig. A) copyright Murdoch Childrens Research Institute and the Gene Technology Access Centre

Image (Fig. B) copyright National Library of Medicine (NLM)

Note: Copyright Information: The MyotonicDystrophy.info Website is A FREE Information sharing site For MYOTONIC DYSTROPHY.
All Effort has been taken to ensure the Integrity and Accuracy
of Information posted on this site.
Any reuse of Posted Information may be subject to
Approval by Owner of any Copyrighted Material.

Posted by Jerry Milliken
Saturday, 04 November 2006
How is myotonic dystrophy inherited? This condition follows a 'dominant' inheritance pattern, which means that on average half of the children of an affected person are themselves affected. Both men and women are equally likely to be affected and to pass on the disorder, but affected women are more likely to have a severely affected child. In general (though not always) the disorder tends to be more severe in successive generations. Autosomal "dominant" traits For these traits only ONE copy of the mutated allele is needed for an individual to be affected, and this can be inherited from either parent. Indviduals with a dominant trait have a 1 in 2 chance of passing that allele, and therefore that trait, on to each of their children. Examples of conditions that are inherited as autosomal dominant traits include Huntington disease, myotonic dystrophy and achondroplasia (a form of dwarfism). *In this example (Fig. A), a Mother with an autosomal dominant disorder has two affected children and two unaffected children.* Fig. A In this example (Fig. B), a Father with an autosomal dominant disorder has two affected children and two unaffected children. *Fig. B* Most healthy adult relatives will not be likely to develop or pass on the disorder, but a careful assessment by an expert is important as mild features can easily be missed. Genetic testing on a blood sample for such relatives can now provide greater certainty, but should always be done with full information as part of genetic counselling. Genetic testing of healthy young children is not recommended. Very few cases of myotonic dystrophy occur 'out of the blue'. Almost always, one parent proves to be affected, often very mildly. Some parents (or grandparents) prove to carry a very slight genetic change that will never give them symptoms. Careful study of the whole family often shows more members to be affected than would appear likely at first. Reference, Professor Peter S Harper, University of Wales College of Medicine, Cardiff for the Muscular Dystrophy Campaign Reference, National Library of Medicine (NLM) Reference, Murdoch Childrens Research Institute and the Gene Technology Access Centre *Image (Fig. A) copyright* Murdoch Childrens Research Institute and the Gene Technology Access Centre Image (Fig. B) copyright National Library of Medicine (NLM) Note: Copyright Information: The MyotonicDystrophy.info Website is A FREE Information sharing site For MYOTONIC DYSTROPHY. All Effort has been taken to ensure the Integrity and Accuracy of Information posted on this site. Any reuse of Posted Information may be subject to Approval by Owner of any Copyrighted Material.
Last Updated ( Friday, 17 August 2007 )

Myotonic Dystrophy Information

Latest Articles

Latest Message Board Posts

Most Popular Articles

Main Menu

How is myotonic dystrophy inherited?

Upcoming Events

News Flash

Calendar