Genetics and Syndromes Flashcards
How does the extra chromosome 21 come about?
meiotic nondisjunction (94%)
translocation (5%)
mosaicism (1%)
What are the clinical features of downs syndrome?
hypotonic at birth flat occiput single palmar crease incurved fifth finger wide sandal gap between big and second toe epicanthic folds small ears small mouth and protruding tongue brush field spots in the iris upslanted palpebral fissure
What are the IMMEDIATE associated medical problems with downs syndrome?
immediately - duodenal atresia, congenital heart disease and Hirschsprungs
How is the diagnosis of Downs syndrome made?
if not diagnose antenatally it may be suspected at birth due to physical appearance
senior paediatrician should review and a blood test for chromosome analysis should be ordered after the parents have been informed that their child is having the test test takes 1-2 days using rtPCR or FISH
What are the clinical features of Turners syndrome (45, X)?
ONLY IN FEMALES SHORT STATURE CHD especially coarctation of the aorta lymphoedema of the hands and feet spoon shaped nails (IMP) wide carrying angle widely spaced nipples congenital heart defects delayed puberty ovarian dysgenesis hypothyroidism renal abnormalities pigmented moles recurrent otitis media normal intellectual function in most cases
What are the later medical problems associated with Downs syndrome?
learning difficulties - may be severe
short stature
hearing impairment
secondary to otitis media
visual impairment from cataracts, squints, myopia
increased risk of leukaemia and solid tumour
increased susceptibility to infections
epilepsy
early-onset alzheimers
obstructive sleep apnoea
increased risk of hypothyroidism and coeliac disease
How is Turner’s syndrome diagnosed?
Antenatal USS shows fetal oedema of neck, hands or feet or cystic hygroma
Chromosome analysis shows 45 chromosomes with one X in 50%
What are the long term management options for Turners?
growth hormone therapy
oestrogen replacement for development of secondary sexual characteristics at the time of puberty
Why is genetic counselling important?
support and provide information for families:
- help them understand their situation
- make their own decisions
- adjust to their situation of being affected by the gene
What are the key features of fetal alcohol syndrome?
growth restriction
characteristic face
developmental delay
cardiac defects
What is fragile X syndrome?
moderate-severe learning difficulty in males mean IQ 50 macrocephaly macro-orchidism characteristic face mitral valve prolapse joint laxity scoliosis autism
What are the clinical features of Marfans?
connective tissue disorder long limbs tall thin scoliosis pectum excavatum/barrel chest flexible joints striae aortic enlargement affects bone, joints, blood vessels, eyes
How does Retts present?
Stage 1 : slow development, hypotonia, difficulty feeding, abnormal head movements, poor coordination
Stage 2 = REGRESSION: at 1-4 years old, loss of abilities, social withdrawal, repetitive uncontrollable hand movements
Stage 3 = PLATEAU: hypotonic, may develop epilepsy, arrhythmias, breathing difficulty
Stage 4 = DETERIORATION: scoliosis, spasticity
What are the clinical features of Duchenne Muscular Dystrophy?
affects males (F may be mildly affected)
- progressive proximal muscle weakness
- difficulty walking, running
- “Gowers sign” uses hands to help get up
- some have learning difficulty
How is Duchenne Muscular Dystrophy tested for?
creatinine kinase 10-100x normal
muscle biopsy
genetic tests
can use splints, oral steroids, may need a wheelchair
