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DiGeorge Case Offers Example of Genetic Compensation

Report points to importance of investigations in parents of child with genomic disorder

WEDNESDAY, March 18 (HealthDay News) -- Cytogenetic studies of the family of a child with DiGeorge syndrome highlights a case of genetic compensation, according to a report published in the March 19 issue of the New England Journal of Medicine.

Nadege Carelle-Calmels, Ph.D., of the Strasbourg University Hospital in Strasbourg, France, and colleagues describe the case of a newborn with DiGeorge syndrome, also known as velocardiofacial syndrome or 22q11.2 deletion syndrome. The girl had facial dysmorphism and absent thymus but no evident cardiac malformation.

Their analysis revealed a 22q11.2 deletion on one copy of chromosome 22 and a reciprocal 22q11.2 duplication on the other copy in the girl's father. Gene expression in the region associated with the syndrome was halved in the girl. However, expression of these genes were similar in the father's and mother's lymphocytes, indicating that the duplication in the father balanced out the phenotypic effects of his deletion, the report indicates.

"Genetic compensation in the context of genomic disorders has tremendous clinical consequences for genetic counseling, given the 100 percent risk of unbalanced outcomes. Our case report highlights the importance of performing genetic investigations in both parents of any child presenting with a genomic disorder, even if the parents have normal phenotypes," the authors conclude.

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