Clinical genetics and dysmorphic children Flashcards
What % of Down syndrome is trisomy 21 and what are the others?
T21 - 95%
Translocation 3%
Mosaic 2%
Describe some dysmorphic features of Down syndrome
No epicanthic fold
Sandal gap toes
Simian palmar crease
What is trisomy 13 also called and what are the features?
- Is patau syndrome
Microcephalic, small eyes, cleft lip/palate, polydactyly, scalp lesions,
Congenital heart/ renal.
What is trisomy 18 called and what are the features?
18- Edwards Over-lapping fingers Rocker-bottom feet Heart/renal defects Micrognathia Low set ears
What is the karotype for turners syndrome and what are its features?
47 X0 Coarctation of the aorta Wide nipples Webbed neck Infertility
What’s the karyotype for klinefelters?
47XXY
Male, tall, female fat distribution, sterile, lower iq and speech delay
Which two syndromes do we see the deletion of 15q11-q13 but different outcomes?
Prader-willi (paternal)- obesity and learning difficulties
Angelman (maternal)- development delay, hyperactive, flaps hands, widely spaced teeth
This mode of inheritance is called imprinting
What is velocardiofacial syndrome?
Abnormal pharyngeal arch, e.g. Cleft
Cardiac abnormalities (outflow)
Deletion of 22q11.2
Shprintzen and digeorge are examples
Di George has: CATCH C- cardiac abnormalities A- abnormal facies T- thymic aplasia C- cleft palate H- hypocalcemia/ hypoparathyriod
What’s the carrier rate for CF gene in Caucasian population?
1/25 carrier (AR inheritance) incidence 1/2500
What are the important X-linked conditions to know about?
Haemophilia
Duchenne muscular dystrophy
Colour blindness
Fragile x (cgg triplet repeat)
What are the important AD linked genetic condictions?
Neurofibromatosis Marfans Huntingtons Achondroplasia Tuberous sclerosis
What can be used for rapid diagnosis of trisomy 21?
Fish - fluorescence in situ hybridisation
Prenatal and postnatal
When cells are in interphase
Risk of Down syndrome in a 40 year old?
1/100 (1/110)
What are acrocentric chromosomes? Which numbers are they?
Chromosomes where the centromere is located near one end and not in the middle.
13 14 15 21 and 22
Robersonian translocation can only happen on acrocentric chromosomes! E.g. 14:21, 21:21
What are the features of noonan syndrome?
Webbed neck, Pectus excavartum, short stature, pulmonary stenosis.
What are the features of Pierre-robin syndrome?
Cleft palate
Micrognathia
Posterior displacement of the tongue
What are the features of Williams syndrome?
Short stature Learning difficulties Friendly - extroverted - cocktail party Transient hypercalcaemia Supravalvular aortic stenosis
What Are the features of prader-Willi?
Obesity
Hypogonads
Hypotonia
What are the features of fragile x? What is the codon repeat?
Larning difficulties Macrocephalic Lond fsce Large eArs Macro-orchidism
CGG triplet repeats
What is ‘anticipation’ when referring to an AD inheritance?
Gets worse with each generation. More codon or nucleotide repeats.
E.g. Myotonic dystrophy
What gene is linked to achondroplasia and what is the inheritance pattern?
FGFR3 gene
Autosomal dominant
Which diseases are x-linked?
Duchene muscular dystrophy
Haemophilia
Colour blindness
What are the features of duchenne Muscular dystrophy?
Delayed walking, progressive weakness,
Proximal muscle weakness
Gower sign (pt ‘walks’ there hands up there body to go from squatting to upright)
High CK (creatinine kinases)
Gene -dystrophin gene Xp21
Starts from about 4, worsens, often can’t walk by 12. Paralyses by about 20. Average Life expectancy 26.
Which syndrome has macrocephaly as a major characteristic?
Fragile x
What is potters syndrome?
Bilateral renal angenisis,
Oligohydramnious
