Friday, 15 October 2010

MRCP revision battle 30.4: Trinucleotide repeat disorders

Trinucleotide repeat disorders are conditions in which 3 nucleotides in the DNA are expanded.

The most 'famous' are:
  • Huntingtons chorea (CAG) - covered in next battle
  • Fragile X (CGG)
  • Myotonic dystrophy (CTG) - covered in previous battle
  • Friedreichs ataxia (GAA) - covered in battle 30.6

Two concepts to be born in mind for trinucleotide repeat disorders are:

= the disease presents earlier and is worse in successive generations

Somatic instability = expansion increases as patient gets older

So lets briefly cover the most famous, Huntingtons...