Genetics Flashcards
What is Klinefelter syndrome
one or more extra chromosome - 47 XXY
What is the phenotype of klinefelter syndrome
tall stature and long legs infertility small testes gynaecomastia learning difficulties
treatment with testosterone to develop secondary sexual characteristics
What is patau syndrome
trisomy 13
What is the phenotype of patau syndrome
• Structural defect of brain • Scalp defects • Small eyes, missing eyes and other eye defects • Cleft lip and palate • Polydactyly • Cardiac and renal malformations macrocephaly low set ears
most will die in early childhood
What is turners syndrome
45X0 (loss of one X chromosome)
What is the phenotype of turners syndrome
• Lymphoedema of hands and feet in neonates which may persist • Spoon shaped nails • Short stature – cardinal feature • Neck webbing or thick neck • Widely spaced nipples • Congenital heart defects – coarctation of the aorta • Delayed puberty • Ovarian dysgenesis resulting in infertility also pregnancy may be possible with IVF • Hypothyroidism • Renal abnormalities • Pigmented moles • Recurrent otitis media • Normal intellectual function in most small mandible
How would you manage turners syndrome
Start oestrogen aged 11
start progesterone at end of puberty
may need IVF for pregnancy
heart surgery
What is Down syndrome
Trisomy 21
can be caused by nondisjunction, translocation, mosaicism
What is the down syndrome phenotype
Dysmorphic facial features: • Round face and flat nasal bridge • Upslanted palbebral fissures • Epicanthic folds • Brushfield spots in iris • Small mouth and protruding tongue • Small ears • Flat occiput and third fontanelle
Other anomalies:
• Short neck
• Single palmar creases, incurved fifth finger and wide sandle gap between toes
• Hypotonia
What other conditions are children with down syndrome more prone to
- Congenital heart defects (40%)
- Duodenal atresia
- Hirschsprung disease
Later medical problems:
• Delayed motor milestones
• Moderate to severe learning difficulties
• Small stature
• Increased susceptibility to infections
• Hearing impairment from secretory otitis media
• Visual impairment from cataracts, squints and myopia
• Increased risk of leukaemia and solid tumours
• Risk of atlanto-axial instability
• Increased risk of hypothyroidism and coeliac disease
• Epilepsy
• Alzheimers disease
What is Edwards syndrome
trisomy 18
What is the phenotype edwards syndrome
Microcephaly
prominant occiput
ocular abnormalities
short sternum
small mouth, jaw (micrognanthia) and neck
‘Rocker-bottom’ feet (flexed big toe and prominant heels) and flexed, overlapped fingers
cardiac and renal malformations
What is fragile X syndrome
X linked recessive disorder.
A trinucleotide repeat disorder. Expansion of triplet repeat CGG in FRAXA gene FMR1
What is the phenotype of fragile X syndrome
Facial: broad forehead elongated face large prominent ears strabismus highly arched palate
Other features: • Learning difficulty (IQ 20-80) mean 50 • Autistic features • Hyperactivity • Macro-orchidism (abnormally large testes) • Mitral valve prolapse • Joint laxity
What is Duchenne muscular dystrophy
an X-linked inherited disorder caused by a deletion on the short arm of the X chromosome (at the Xp21 site). This site codes for a protein called dystrophin
What is the phenotype of duchenne muscular dystrophy
floppy baby
waddling gait
language delay
Gowers sign
The progressive
muscle atrophy and weakness means that they are no
longer ambulant by the age of about 10–14 years. Life
expectancy is reduced to the late twenties from respiratory
failure or the associated cardiomyopathy. About
one-third of affected children have learning difficulties.
Scoliosis is a common complication.
Management of duchenne muscular dystrophy
orthoses
physiotherapy
steroids
What is angelmans syndrome
• Caused by a deletion in the Maternally inherited chromosome 15 or paternal uniparental disomy
What is the phenotype of angelmans syndrome
- “Happy puppet” unprovoked laughing/clapping
- Microcephaly
- Mental retardation
- Seizures
- Ataxia
- Broad based gait
What is prader willi syndrome
• Caused by a deletion in the paternally inherited chromosome 15 or maternal uniparental disomy
What is the phenotype of prader willi syndrome
- Neonatal hypotonia and poor feeding
- Failure to thrive in infancy
- Hypogonadism
- Developmental delay
- Moderate Mental Retardation
- Hyperphagia and obesity
- Small genitalia
What is noonan syndrome
Autosomal dominant disorder
What is the phenotype of Noonan syndrome
• Occasional mild learning difficulties
• Short webbed neck with trident hair line
curly/wooly hair
• Pectus excavatum
• Short stature
• Congenital heart disease – especially pulmonary stenosis and atrial septal defects
What is williams syndrome
Microdeletion of the elastin gene
What is the phenotype of williams syndrome
• Short stature • Transient neonatal hypercalcaemia • Congenital heart disease (supravalvular aortic stenosis) • Mild to moderate learning difficulties Sunken nasal bridge puffiness around the eyes epicanthal fold blue eyes starry pattern long upper lip length small and widely spaced teeth wide mouth prominent lower lip small chin
