Genetics Flashcards
Down syndrome
Aetiology
Non- Dysjunction (94%)
failure of the chromosomes to separate in M1 or M2 –> trisomy
Risk ^ with maternal age
Translocation (robertsonian 14)
Parents need testing
there are 3 copies on 21 just on sits on 14 (or 15, 22)
Mosacism –> non-dysjunction in the normal cells –> leads to a milder phenotype
Down Syndrome
Presentation
Craniofacial features Flat nasal bridge Epicanthic folds Upslanting palpable fissures Brushfield spots Small mouth Pseudomacroglossia Flat occiput
Single palm crease
Sandal gap
GI - reflux, duodenal atresia, hischprungs
Neuro - learning disabilities, cataracts (etc), hearing loss, motor delay
Cardiac - ASD (+VSD, TOF)
Increase risk of SHELAC-T Subfertility Hypothyroid Epilepsy Leukaemia Alzheimers (early onset) Coeliac T1DM
Down syndrome - increased risk of what diseases
SHELAC T Subfertility Hypothyroid Epilepsy Leukaemia Alzheimers Coeliac
T1DM
Down syndrome screening and testing
11-13+6 weeks - combined - is the gold standard
- Nuchal thickness ^
- HcG ^
- PAPP-A - decreased
15-20w
- hCG - increased
- AFP - decreased
- oestradiol - decreased
- Inhibin A - increased
If the screening is +ve they can then go on to have a diagnostic test (comes with risks eg miscarriage)
Amnioscentesis - 15-20w (more accurate, lower risk)
CVS 11-13w
NIPD - maternal blood - tests for foetal DNA -?not on the NHS yet
Down syndrome management
MDT approach
Screening for Thyroid Coeliac Hearing Eyes Dental
Turners syndrome
45X
Webbed neck Short stature Always female Shield chest pigmented moles lymphadenopathy hands and feet Ovarian dysgenesis/ primary amenorrhoea Spoon nails Cardiac abnormalities - CoA - Biscuspid aortic valve Renal abnormalities High arched palate
Associated with other X linked conditions
Klinefelter
XXY
Tall Hypogonadism Gynaecomastia Infertility Delayed puberty Small testes raised gonadotrophin
Patau
Trisomy 13
Celft palate Holoprosencepahly Microophthalmia Anophthalmia Coloboma Cardiac abnormalities - VSD Renal abnormalities Polydactyly
Edwards
Trisomy 18
Prominent occiput Small eyes Micrognathia Cardiac and renal ab Flexed overlapping fingers Syndactyly Rockerbottom feet
Prader willi
Paternal deletion in 15 Fat floppy baby Obesity Hyperphagia hypotonia hypogonadism
Angelmans
Maternal deletion in 15 Happy clapper - unprovoked laughing and clapping Water fascination Siezures Ataxia broad based gait almond face
William syndrome
Chromosome 7 - microdeletion
Elfin like face Very friendly Short stature Transient neonatal hypercalcaemia Supravalcular aortic stenosis
Noonan
webbed neck sheild chest pectus excavatum Cardiac - ASD - Pulmonary stenosis
Fragile X
X linked - CGG trinucleotide repeat
hypotonia
macroorchidism
Prominent mandible
Broad forehead
Mitral valve prolapse
scoliosis
X linked examples
Fragile X Colour blind Haemophilia Duchennes G6PD Hunter syndrome
