HD PBL 6 Flashcards
Define aneuploidy.
presence of abnormal number of chromosomes in a cell
What is the karyotype of the boy in this scenario?
47 X,Y
With trisomy 21
What are the characteristics of Down’s syndrome?
- physical growth delay
- mild to moderate intellectual disability
- characteristic facial features (slanted eyes, palmar crease)
What are the neurological complications of Down’s Syndrome?
- cognitive impairment
- early onset AD
What are the physical complications of Down’s Syndrome?
- stunted growth
- short stature
- hypotonia
What are the senses affected in Down’s Syndrome?
- strabismus (cross-eyed)
- congenital cataracts
- hearing problems (otitis media)
What are the endocrine complications of Down’s Syndrome?
hypothyroidism
What are the cardiac complications of Down’s Syndrome?
- CHD
- AVSD
- VSD
- ASD
- PDA
- Tetralogy of Fallot
What are the GI complications of Down’s Syndrome?
- Hirschsprung’s
- Duodenal atresia
- Pyloric stenosis
- Imperforate anus
Explain the genetic basis of DS.
- Non-disjunction occurs in 94% of cases
- -> where the chromosomes fail to separate from each other during cell division
- Robertsonian translocation occurs in ~5% of cases
- -> 10-15% recurrence if mother is a carrier and 3-5% if father is a carrier
- Mosaicism in ~1% of cases
- -> when some cells are normal and some have trisomy 21
Explain the mechanism of a Robertsonian translocation.
- due to breakage of 2 acrocentric chromosomes at, or close to, their centromeres
- subsequent fusion of long arms
- short arms of each chromosome are lost
- total chromosome number reduced to 45
- if there is no gain/loss of important genetic material = Robertsonian translocation carrier who will appear norma l
What are the possible outcomes of a Robertsonian 14/21 translocation?
- trisomy 21
- monosomy 14
- trisomy 14
- monosomy 21
(last 3 are lethal)
How can DS lead to early-onset Alzheimer’s disease?
- chromosome 21 carrier amyloid precursor protein
- therefore trisomy 21 may upregulate the formation of amyloid plaques
- autopsies have shown that, by the age of 40, DS individuals have plaques + neurofibrillary tangles
What tests are offered ~8-12 weeks of pregnancy?
- Offer foetal screening for DS (ultrasound)
- ‘combined test’:
1. nuchal translucency
2. serum 𝜷HCG
3. serum pregnancy-associated protein A
(offered up to 13 weeks + 6 days)
What is involved in the ‘triple test’ offered at 15-20 weeks?
- plasma levels of HCG
- unconjugated oestradiol
- alpha-fetoprotein
What is involved in the ‘quadruple test’ offered at 15-20 weeks?
- 𝜷HCG
- unconjugated oestradiol
- alpha-fetoprotein
- inhibin A
What antenatal testing can be done for DS?
- Nuchal translucency scan (translucency will be raised in DS)
- Amniocentesis (15-20 weeks)
- Chorionic villous sampling (11-14 weeks)
Why should people with DS avoid headstands?
- have atlanto-axial instability
- can lead to spinal cord compression
Who is involved in the MDT for children with DS?
- Paediatrician
- Physiotherapist
- Occupational therapist
- Speech and Language
therapist - Child psychiatrist/Psychotherapist
- Social worker
- Audiologist
- Orthoptist
- Ophthalmologist
- Dietician.
What are the roles of the MDT in caring for children with DS?
- Providing information to parents (of DS services)
- Developmental assessment
- Non-medical therapy
- Medical assessment and treatment
- Liaison with the local education authority
- Advice on accessing social support
What kind of developmental delay does the child in this scenario have?
global developmental delay
- fine motor, gross motor, social, speech + language
A newborn boy with DS is vomiting all of his feeds. What is the most common cause of this?
Duodenal atresia
A 27 year old woman who is 12 weeks pregnant attends the antenatal clinic for the results of her nuchal translucency scan and serum screening tests. The results reveal she has an increased nuchal translucency and decreased pregnancy-associated plasma protein A (PAPP-A) levels. What is the single most appropriate intervention at this point and why?
- Chorionic villous sampling
- high risk of having a baby with DS
- CVS will give definitive karyotyping
What is the portage scheme?
Portage is a home-visiting educational service for pre-school children with additional support needs and their families.
