Pediatric Patient Resources

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Original Editors - Alicia Dupilka, Elaine Lonnemann, Kim Jackson, Leana Louw, WikiSysop, Admin and Scott Buxton

Resources for Physiotherapists and the Families of their Pediatric Clients

Down's Syndrome

Definition: Genetic disorder occurring when the individual has full or a partial copy of chromosome 21. This extra genetic material causes an alteration in the development of the child.

How common is it?
• Most common genetic disorder
• ~1:691 babies are born each year with Down’s Syndrome
• ~6,000 babies are born each year with Down’s Syndrome

Types
• Trisomy 21 (Nondisjunction)
     o The pair of the 21st chromosome fails to separate
     o Extra chromosome is replicated in every cell in the body
     o Accounts for ~95% of cases

• Mosaicism
     o Nondisjunction takes place in chromosome 21 in one cell but not all cells
     o Accounts for ~1% of cases
     o May have fewer characteristics than other types of Down’s Syndrome

• Translocation
     o Part of chromosome 21 breaks off during cell division and attaches to another chromosome, typically chromosome 14
     o Accounts for ~4% of cases

Causes
     • Cause of nondisjunction is currently unknown
          o Research suggests the likelihood increases as women age
          o No definitive research suggesting environmental factors of the parents before or during pregnancy

How is Down’s Syndrome Diagnosed?
     • Prenatally
          o Screening tests
                Most only provide a probability
                Blood test: measures quantities of various substances in the mother’s blood
                Ultrasound: checks for “markers”
          o Diagnostic tests
                Can provide a definite diagnosis with almost 100% accuracy
                Carry up to a 1% risk of causing a spontaneous termination
                Chorionic villus sampling (CVS): usually performed in first trimester between 9 and 11 weeks
                Amniocentesis: usually performed in the second trimester after 15 weeks
     • At birth
          o Usually identified by certain physical traits
                Low muscle tone
                Single deep crease across the palm of the hand
                Slightly flattened facial profile
                Upward slant to the eyes
          o Chromosomal analysis may also need to be done to confirm the diagnosis
                This is done by drawing a sample of the baby’s blood