13. Genetics + 14. Developmental delay Flashcards
When might you consider genetic testing for a child?
- Presence of features of a genetic disorder eg Down’s
- Asymptomatic but at risk of a genetic condition for which preventative / therapeutic measures are available (especially if typical onset is in childhood)
- Must be in child’s best interest
When would genetic testing be inappropriate?
- If child is at risk of a genetic condition for which typical onset is in adulthood and therapeutic measures are not available eg Huntington’s - child’s autonomy is paramount
- Testing carrier status
- Testing of a child for the benefit of another family member (unless to prevent substantial harm)
What different genetic tests are available?
Chromosome tests:
-Karyotype analysis
-Fluorescence in situ hybridisations
-Molecular karyotyping using microarrays
Molecular Genetic analysis:
-Highly specific, info about one very specific gene eg a commonly occurring / known family mutation
What causes Down’s syndrome?
-Part or all of a third copy of chromosome 21
-Occurs by non-disjunction during meiosis
-Usually maternal chromosome (hence incidence increases with maternal age)
What clinical features does Down’s syndrome have?
FACIAL
-Small low-set ears
-Upslanting palpebral fissures
-Flat facial profile
-Protruding tongue
-Brushfield’s spots on the iris (white)
-Flat occiput, short neck
LIMBS
-Short, broad hands + short incurved pinkies
-Single transverse palmar crease
-Wide sandal toe gap
-Short stature
COGNITIVE
-Intellectual impairment (IQ = 25-70)
-Social skills often exceed intellectual skills
What further associated conditions does Down’s syndrome have?
CONGENITAL HEART DISEASE (40-50%)
-AVSD (or just ASD / VSD)
-Tetralogy of Fallot
GI
-Duodenal / anal atresia
-Hirschprung’s disease
-Increased infection risk
-Umbilical hernia
OTHER
-DDH
-Eczema
-Deafness, cataracts
-Hypothyroidism
How do you test for Down’s syndrome?
-Combined test done 11-13+6 weeks
–Triple / quadruple done later
-Diagnosis confirmed postnatally on karyotyping / FISH
How can Down’s be managed and what is its prognosis?
Refer for:
-Cardiac assessment
-Hip USS
-Audiology
Other management:
-Genetic counselling
-Refer to support organisations
-Physio
-Audiology / ophthalmic assessment
Prognosis:
-Life expectancy well into adult life (unless congenital heart disease is present)
-Most develop Alzheimer’s by age 40
What is the difference between strabismus and amblyopia?
-Strabismus = squint / cross-eyed
-Amblyopia = lazy eye, poor vision in 1 or both eyes
–Feature of strabismus
What are the diagnostic factors for a squint?
-Diplopia
-Amblyopia
-Eye misalignment
What are squints categorised?
PARALYTIC (rare)
-Squint varies with direction of gaze
-Paralysis of extra ocular muscles, usually due to CN palsy
NON-PARALYTIC / CONCOMITANT
-Squint constant in all directions of gaze
-Due to refractive error in one/both eyes and imbalance of extra ocular muscles
-Often convergent ie bad eye turns inwards but can be divergent
-Can be manifest (obvious at all times) or latent (when tired)
How should you investigate a squint?
-If >12 weeks, should be investigated with full ophthalmic examination
–Cover test = cover + uncover good eye, squint will flick in a certain direction when uncovered
–Assess for diplopia
–Corneal reflection symmetry can be done for non-cooperative children
How should a squint be managed?
-Should be treated to avoid worsening of vision in the affected eyes –> amblyopia
-Refer to ophthalmology:
–Spectacles for refractive error correction
–Patching of good eye to prevent amblyopia of bad eye
–Surgical rectus muscle alignment correction
What are the features of autistic spectrum disorder and Asperger’s disease?
AUTISTIC SPECTRUM DISORDER:
-Poor verbal + non-verbal communication
-Obsessive intense repetitive interests
-Reduced imaginative play
ASPERGER’S
-Milder form with no communication difficulties
-Normal or increased IQ
-Narrow niche interests
What can cause autism?
-Mostly idiopathic
-Down’s syndrome, fragile X syndrome
-Tuberous sclerosis
-Muscular dystrophy
-Cerebral palsy
-Neurofibromatosis
-Premature birth, older parent male
How can autistic spectrum disorder present?
-Communication difficulties + impaired imagination:
–Delay in speech development
–Echolalia (repeating what you say)
–Neologisms
–Abnormal rate, rhythm pitch of speech
-Lack of modulation of behaviour to fit social context
-Hyper-responsive to stimuli
-Restricted, obsessive, repetitive behaviours
-Social anxiety
-Preoccupations and unusual attachments
-Distress with environmental changes
-Sensory mis-wiring eg confusing taste + smell
-Learning difficulties
How can autism be diagnosed?
-Observe in school and at home
-Developmental history and detailed parent + teacher discussion
How can autism be managed?
-Specialist education support
-Management of associated conditions eg anxiety, hearing / visual defects
-Behavioural management
-Parent education
-SALT
How are sight impairment and blindness defined?
-Sight impaired = visual acuity <6/60
-Blind = visual acuity <3/60
What can cause childhood blindness?
GENETIC
-Cataracts - congenital rubella
-Albinism
-Retinal dystrophy
-Retinoblastoma
ANTENATAL / PERINATAL CAUSES
-Congenital infection
-Retinopathy of prematurity
-Cerebral damage
-Optic nerve hypoplasia
POSTNATAL
-Trauma
-Infection
-JIA
-Vitamin A deficiency
How might childhood blindness present?
-Abnormal appearance or movement of eyes (especially purposeless in neonates)
-Altered psychomotor development
-Lack of eye contact, don’t turn towards sound
-Not smiling by 6 weeks
-Delayed reaching out for objects / pincer grip
-Eye poking + rubbing
-Associated with hearing deficits or severe LD
How can childhood blindness be managed?
-Early intervention
-Non-visual stimulation using speech + touch
-Ensure safety of home environment
-Noisy shoes
-Additional assistance at school
-Braille reading
What can cause childhood deafness?
CONDUCTIVE = abnormalities of ear canal / middle ear
SENSORINEURAL = lesion in cochlea or auditory nerve
-Most mild-moderate causes are conductive, secondary to OTITIS MEDIA
-Sensorineural deafness may be genetic + result from pre- and perinatal problems / following cerebral insult
How does childhood deafness present?
-Often picked up on screening
–Newborns
–7-8 months distraction test
–3-4 years pure tone audiometry
-Further audiological testing done for children at risk or with delayed speech (/ if parents suspect)
MANIFESTATIONS:
-Lack of response to sound
-Delayed speech
-Behavioural problems
-Associated with LD, neuro disorders, visual defects
