Genetic conditions Flashcards
(42 cards)
Features of tetralogy of fallot
ventricular septal defect (VSD)
right ventricular hypertrophy
right ventricular outflow tract obstruction, pulmonary stenosis
overriding aorta
What is the most common cause of cyanotic heart disease in infants
Tetralogy of Fallot
- typically presents at around 1-2 months (may not until 6 months old
What is the management of tetralogy of fallot
Surgical repair is often undertaken in two parts
cyanotic episodes may be helped by beta-blockers to reduce infundibular spasm
Clinical features of down syndrome
face: upslanting palpebral fissures, epicanthic folds, Brushfield spots in iris, protruding tongue, small low-set ears, round/flat face
flat occiput
single palmar crease, pronounced ‘sandal gap’ between big and first toe
hypotonia
congenital heart defects (40-50%, see below)
duodenal atresia
Hirschsprung’s disease
Cardiac complications in down syndrome
multiple cardiac problems may be present
endocardial cushion defect (most common, 40%, also known as atrioventricular septal canal defects)
ventricular septal defect (c. 30%)
secundum atrial septal defect (c. 10%)
tetralogy of Fallot (c. 5%)
isolated patent ductus arteriosus (c. 5%)
Non cardiac complications in down syndrome
subfertility: males are almost always infertile due to impaired spermatogenesis. Females are usually subfertile, and have an increased incidence of problems with pregnancy and labour learning difficulties short stature repeated respiratory infections (+hearing impairment from glue ear) acute lymphoblastic leukaemia hypothyroidism Alzheimer's disease atlantoaxial instability
What causes trisomy 21
3 copies pf chromosome 21
What is the genetic mechanism
maternal meiotic non-disjunction (95%)
What immediate health concerns must you rule out with down syndrome
cardiac anomalies - avsd
Bowel obstruction - duodenal atresia/hirshsprungs
How do you diagnose trisomy 21
rapid aneuploidy screen - once this confirms down syndrome, you would carry out karyotyping
Key features of down syndrome in neonates
hypotonism sleepy - difficult to wake for feeds epicanthic folds small ears protruding tongue excess nuchal skin hypo-pigmented iris pseudo strabisus (caused by epicanthic folds)
What is the most common cardiac anomaly in down syndrome
atrial ventricular septal defect
other septal and valvular defects are common
40% of down syndrome babies have a cardiac anomaly
What other features may be picked up on screening that are associated with trisomy 21
conductive and sensorineural hearing defects
hypothyroidism
which markers prenataly may indicate down syndrome
AFP - lower
unconjugated oestriol - lower
Inhibin A
human chorionic gonadotrophin - higher
which chromosomes does rapid aneuploidy screen (RAS) look at?
13, 18, 21 and sex
What does trisomy 13 (Patau) cause
- Holoprosencephaly - no hemispheres in brain
- orofacial clefts
- polydactyl
What does Edward syndrome (18) cause
- prenatal growth deficiency
- over-riding fingers
- congenital heart disease
What is a robertsonian translocation
2 chromosomes lose their short arms and the long arms join together
What is mosiacism
effected gene not present in every ceel in the body
What is a point mutation
A base pair is altered. Can either be:
- silent mutation - same amino acid
- Missence - altered codon corresponds to a different amino acid
- nonsense- altered codon corresponds to a stop signal
What is fragile X
Mutation which prevents the development of fragile X mental retardation protein.
It affects both male and females but males tend to have more severe features
What are the features of fragile x
intelectual disability
delayed motor ability
behavioural problems
toe walking
What type of genetic condition is fragile X
X linked dominant CCG trinucleotide repeat
What are 2 adult osnet disorsders associated with fragile X
- fragile X tremor-ataxia syndrome (FXTAS)
- primary ovarian insufficiency (POI
