Edwards syndrome

• Trisomy 18
• Small head, small jaw
• Clenched fists

Di George syndrome

• Part of chromosome 22 is deleted
• Developmental difficulties
• Thymic aplasia - lack of T cells
• Features - CATCH-22 mnemonic 
  • C – Congenital heart disease
  • A – Abnormal facies (characteristic facial appearance)
  • T – Thymus gland incompletely developed
  • C – Cleft palate
  • H – Hypoparathyroidism and resulting Hypocalcaemia
  • 22nd chromosome affected

Patau syndrome

• Trisomy 13
• Cleft lip/palate
• Cerebral defects
• Trigger thumbs
• Polydactyl

Down's syndrome

• Trisomy 21
• Flattened appearance to face
• Small ears, short neck

Turner syndrome

• 45, X
• therefore female only
• Normal life expectancy
• Behavioural, socal and some specific learning disabilities

Klinefelter syndrome

• 47, XXY
• Males born with extra X
• Learning difficulties
• More feminine "phenotype"

Mosaic trisomy 8

• Trisomy 8 
• Some cells have 3 copies of C8 others have the 2
• Full trisomy is fatal

Prader-Willi syndrome

• Deletion of paternal chromosome 15

OR

• Two maternal copies of chromosome 15
• Restriction of growth etc - what the maternal body would want when pregnant

Angelman Syndrome

• Deletion of maternal chromosome 15

OR

• Two paternal copies of chromosome 15

Beckwith-Wiedemann Syndrome

• Foetal overgrowth 
• Hypermethylation of H19 on maternal chromosome → reduced expression of maternal H19 → reduced inhibition of maternal IGF2 ⇒ overgrowth/organomegaly

Russell-Silver syndrome

• Growth inhibition
• Hypomethylation of paternal H19 → increased expression of paternal H19 → increased inhibition of paternal IGF2 ⇒ not enough growth

Tay-Sachs disease

• Mutation in HEXA - chromosome 15 → needed for sphingolipid breakdown
• Infantile onset hearing loss + seizures
• Life expectancy of ~4 years