Child health · UKMLA & AKT

Down's syndrome

A free high-yield preview for the UKMLA Applied Knowledge Test. Below are the key points to recognise down's syndrome — the full SA Note notes add investigations, management, complications and 10 practice questions.

Key high-yield points

  • Most common autosomal trisomy compatible with survival - trisomy 21
  • Incidence ~1 in 1,500 at age 20, rising to ~1 in 30 at age 45
  • Three genetic subtypes: free trisomy 21 (non-disjunction, most common), Robertsonian translocation (familial - karyotype parents), mosaicism (milder phenotype)

Translocation Down's syndrome requires parental karyotyping - recurrence risk is significantly higher than free trisomy. Free trisomy 21 does not require parental karyotyping.

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