Microdeletion syndromes

Sub-microscopic deletion of a part of a chromosome (1-3 million bp) that are too small to see on standard microscopy.

Sometimes involves loss of a few contagious genes (contagious gene syndromes).

Sometimes involves micro duplications.

They can be detected using specific FISH testing, MLPA or CGH microarray.

 Examples of microdeletion syndromes:

• DiGeorge syndrome or velocardiofacial syndrome  – most common microdeletion syndrome.
• Prader–Willi syndrome.
• Angelman syndrome.
• Williams syndrome.
• Miller–Dieker syndrome.
• Smith–Magenis syndrome.
• Rubinstein–Taybi syndrome.
• Wolf–Hirschhorn syndrome.
  

- 47, XYY syndrome.

47, XYY syndrome

Also known as Jacobs syndrome

This affects 1 in 1000 live-born boys.

These males are phenotypically normal but tend to be tall.

But affected boys may have hypotonia, hand trembling or involuntary muscle movements, delayed or difficult speech and delayed motor skill development.

Intelligence is usually within normal limits but there is an increased incidence of behavioral abnormalities.

Treatment:

·       speech therapy for speech delay.

·       occupational therapy: for delayed motor skill development.

·       Educational therapy: for learning disabilities.