22q11.2 Deletion Syndrome - Hội chứng DieGeorge

WHAT IS IT? 

• 22q11.2 deletion syndrome is referred to by other names such as 
  • 22q deletion syndrome, DiGeorge syndrome or Velocardiofacial (VCF) syndrome are alternate references 
  • Approximately 1/3000 to 1/6000 children are born with this disorder 
  • While there may be noticeable characteristic facial features in some affected individuals, this syndrome may be missed at birth and can have life threatening consequences, if not diagnosed 
• The syndrome is caused by a loss (deletion) of a small piece of chromosome 22 
• 93% of the time, it is the first case in the family
  • 7% of individuals inherit the deleted chromosome from a parent

What Is a Deletion? 

• Deletions can be large or small, and can occur anywhere along a chromosome 
• If the piece of chromosome is especially small, it is called a ‘microdeletion’ 
• In the case of 22 deletion syndrome, the missing piece of chromosome is very small and is the most common microdeletion syndrome   

What Are the Findings?  

• May affect almost every organ system, but the following findings are particularly common and may be identified on prenatal ultrasound  
  • Congenital heart disease (74%) 
  • Cleft Palate   
    • May not be seen on prenatal ultrasound and may even be missed at birth without careful physical examination 
  • Kidney abnormalities (31%) 
• Other findings may not be obvious at birth but may require immediate attention in the newborn nursery 
  • Problems with the immune system and fighting off infection (77%) 
  • Low calcium levels (50%), which may lead to seizures 
  • Feeding and swallowing problems 

KEY POINTS: 

Screening in Pregnancy for 22q Deletion Syndrome

• Some NIPS tests may include 22q deletion syndrome, although not formally recommended by ACOG and SMFM  
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  • A ‘positive’ 22q deletion syndrome NIPS report (higher risk for 22q deletion syndrome) does not mean that the baby will have 22q deletion syndrome 
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  • In a general population where no other pregnancy problems are identified, only a minority of  pregnancies with a ‘positive’ (increased risk) NIPS report will be affected
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    • Therefore, NIPS cannot be used to diagnose 22q deletion syndrome  
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  • Follow up and pregnancy management should not be based on an NIPS result without confirmation studies  
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• In the case of a NIPS report suggesting increased risk, a diagnostic prenatal test is offered to confirm whether 22q deletion syndrome is present 
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  • Amniocentesis (amniotic fluid is removed and sent to the lab)
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  • CVS (small piece of placenta is removed and sent to the lab)  
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• A special test called a microarray is used to diagnose 22q deletion syndrome  
  • Most amniocentesis and CVS reports will come back normal 
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  • If an amniocentesis report shows a 22q deletion, genetic consultation and multidisciplinary management is advised to maximize the best possible outcome for the baby