The International Myotonic Dystrophy Consortium developed guidelines for genetic testing of individuals with or possibly with myotonic dystrophy. These are based on a number of principles applicable to other genetic disorders.


Indication for Testing

Nonindication for Testing

confirmatory testing in a symptomatic patient

(1) To confirm the diagnosis in a patient with typical symptoms. (2) As part of the diagnostic workup of a symptomatic person in whom the diagnosis is uncertain.


asymptomatic patient

(1) To help identify which parent of an affected person has the gene mutation in order to aid in family counseling. (2) To modify the a priori risk of inheriting the allele.


minor (child or adolescent under the legal age)

(1) Symptomatic minor, for confirmation of diagnosis.

(2) If a compelling reason is present.

Asymptomatic without compelling reason.

prenatal testing of fetal cells

Need to assess fetal risk when a parent is or may be affected (see below).

Parents will have the child regardless of the results.


Prenatal testing of fetal cells:

(1) If one of the parents is symptomatic and has been diagnosed with muscular dystrophy.

(2) If one parent is asymptomatic but has a significant risk of having the condition (based on family studies), then the implicated parent is tested first. If the parent is positive for the condition, then prenatal testing is performed.


Key aspects in testing:

(1) Genetic counseling by a qualified counselor should be available to all persons having the testing and other family members.

(2) The person tested must be able to fully understand the risks and benefits of testing.

(3) If uncertainty exists in the inheritance or other features of the disease, the health care professionals should not try to make predictions for age of onset or severity of the disease.

(4) Confidentiality to ensure that the persons are not subject to discrimination.

(5) Property rights of the DNA sample belong to the individual to whom the sample was obtained.


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