Monday, December 3, 2012

Diagnosis (3/3)

Prenatal diagnosis 

Once an Epidermolysis Bullosa (EB) diagnosis has been confirmed by skin biopsy and molecular genetic studies (DNA analysis) prenatal diagnosis of future pregnancies becomes possible. DNA for prenatal diagnosis can be obtained as a chorionic villi sample as early as the 9th week of gestation. Alternatively, amniotic fluid drawn after the 11th week can provide the necessary DNA.
Following steps are required for prenatal diagnosis of EB:
1.    Biopsy diagnosis of an affected family member is needed to identify EB subtype.
2.    After subtype is identified, DNA sample is sent to lab for identification of the genetic mutation.
3.    After genetic mutation is identified, amniotic fluid or chorionic villus sampling (CVS) is obtained during pregnancy which is sent to the genetic laboratory and evaluated for the previously identified mutation. Placental cells may be obtained through a CVS, performed at approximately 10-12 weeks gestation, and amniotic fluid may be obtained through amniocentesis, at approximately 15-18 weeks gestation.
Many EB parents prefer to have prenatal diagnosis completed utilizing CVS rather than amniocentesis.
Preimplantation genetic diagnosis (PGD) improves the likelihood of an EB-free birth. PGD is accomplished by genetic analysis of a fertilized egg before implantation with the following step:
1.    DNA analysis is performed to identify the genetic mutation present in the affected person.
2.    Hormone injections to the prospective mother to stimulate her ovaries for development of eggs.
3.    The eggs are retrieved from the mother and fertilized with the father’s sperm, usually by a reproductive endocrinology (in vitro fertilization).
4.    When the fertilized egg has developed into at least eight cells, one cell is removed and analyzed in the laboratory to determine whether it carries the genetic mutation present in the affected person.
5.    If the mutation is not detected, the fertilized eggs are implanted in the mother’s womb in anticipation of the birth of a child who does not have EB.

This procedure has resulted in successful outcomes for many EB families but it is expensive. 
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