Dr athal pediatric chromosomal Abnormalities

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  Chromosomal abnormalities are either numerical or structural.
  
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  Chromosomal abnormalities occur in approximately 8% of fertilized ova but only in 0.6% of liveborn infants.
  
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  50% of spontaneous abortuses have chromosomal abnormalities.
  
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  In newborns and older children, many features suggest the presence of a chromosome anomaly, including LBW (SGA), FTT, developmental delay, and the presence of three or more congenital malformations.
  
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  Acquired chromosomal changes play a significant role in carcinogenesis and tumour progression.
  
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  The diagnosis is confirmed by chromosome analysis
  

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  DS is the most common abnormality of chromosomal number. It occurs in 1 of every 1000 births.
  
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  DS considered most common genetic cause of moderate intellectual disability and characteristic dysmorphic features.
  
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  Cytogenetics: the extra chromosome 21 may result from:
  
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    Nondisjunction.
    
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    Translocation.
    
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    Mosaicism.
    

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  Most cases result from an error at meiosis, the pair of chromosome 21s fails to separate, so that one gamete has two chromosome 21s and one has none.
  
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  Fertilisation of the gamete with two chromosome 21s gives rise to a zygote with trisomy 21.
  
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  Parental chromosomes do not need to be examined.
  

Down's syndrome is usually suspected at birth because of the baby's facial appearance.

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  Brachycephaly with flat occiput and third fontanelle
  
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  Round face and flat nasal bridge.
  
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  Upslanted palpebral fissures.
  
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  Epicanthic folds (a fold of skin running across the inner edge of the palpebral fissure).
  
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  Brushfield spots in iris (pigmented spots).
  
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  Small mouth and protruding tongue.
  
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  Small ears.
  

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  Normal BW & length, but hypotonic.
  
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  Short neck
  
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  Short broad hand with single palmar creases, incurved fifth finger.
  
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  Wide 'sandal' gap between 1^st & 2^nd toes.
  
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  Congenital heart defects (40%)
  
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  Duodenal atresia
  
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  Annular pancreas
  
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  Imperforated anus.
  
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  Hirschsprung's disease
  

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  Delayed motor milestones.
  
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  Moderate to severe learning difficulties.
  
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  Increased susceptibility to infections.
  
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  Hearing impairment from secretory otitis media.
  
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  Visual impairment from cataracts, squints, myopia.
  
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  Increased risk of leukaemia and solid tumours.
  
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  Risk of atlantoaxial instability.
  
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  Hypothyroidism and DM.
  
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  coeliac disease
  
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  Epilepsy
  
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  Alzheimer's disease