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22q11 deletion in DGS/VCFS monozygotic twins with discordant phenotypes
M C Vincent1, F Heitz, J Tricoire
1Service de Génétique Médicale & Laboratoire d'Immunogénétique Moléculaire, Université Paul Sabatier Hôpital Purpan, Toulouse, France.
Genetic Counseling (Geneva, Switzerland)
|April 7, 1999
Summary
Monozygotic twins with 22q11.2 deletion showed discordant heart defects. This case suggests complex genetic and environmental interactions, not just somatic mutations, influence 22q11.2 deletion syndrome phenotypes.
Area of Science:
- Genetics
- Developmental Biology
- Clinical Medicine
Background:
- 22q11.2 deletion syndrome presents diverse clinical features.
- Phenotypic variability, especially in monozygotic twins, remains unexplained.
- Proposed mechanisms include mosaicism, environmental factors, and chance events.
Purpose of the Study:
- To investigate the cause of phenotypic discordance in monozygotic twins with 22q11.2 deletion.
- To analyze potential mechanisms underlying variable expressivity of 22q11.2 deletion syndrome.
Main Methods:
- Case report of monozygous twins with 22q11.2 deletion.
- Clinical assessment for phenotypic discordance, specifically heart defects.
- Exclusion of mosaicism and twin-to-twin transfusion syndrome.
Main Results:
- The monozygous twins exhibited discordance for a heart defect.
- No evidence of mosaicism or twin-to-twin transfusion syndrome was found.
- This discordance challenges simple genotype-phenotype correlation models.
Conclusions:
- Phenotypic discordance in 22q11.2 deletion syndrome is not solely explained by somatic mutations.
- A complex interplay between genetic predisposition and environmental influences likely drives phenotypic variation.
- Further research is needed to elucidate the specific environmental factors and their interaction with the 22q11.2 deletion.
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