Learning Disability 1.2 Flashcards
Incidence of Fragile X
1/3000
Most common inherited cause of LD
Fragile X
IQ of most people with Fragile X
<50
How many men with LD have Fragile X?
10-12%
How many children with Fragile X have autism?
50%
Genetics of Fragile X?
Trinucleotide triplet repeat - CGG - on long arm of chromosome X
Which chromosome has the trinucleotide repeat in Fragile X?
Xq27.3-FMR1
What is FMR1 gene needed for?
Normal neural development
Penetrance of Fragile X
Low
Why is Fragile X more common in males?
Protective effects of second normal X chromosome in females
Clinical features of Fragile X
Large head & ears Long, narrow face Short Post pubertal macro-orchidism Hyperextensible joints Seizures
How many people with Fragile X have seizures?
20-25%
Which people with Fragile X have mild LD?
Women
Behavioural features of Fragile X
Hyperactivity Inattention Stereotypies Speech & language delays Repetitive mannerisms Shyness Gaze avoidance Communication difficulties
Brain imaging in Fragile X
Enlarged ventricles, hippocampus & caudate nuclei
Reduced posterior cerebellar vermis
What is higher triplets in Fragile X associated with?
Lesser IQ
When is reduced IQ most pronounced in Fragile X?
Ages 8-12
What is drop in IQ in Fragile X related to?
Higher stress upon abstract difficulties in different IQ tests used in adults vs children
Genetics of Turner X
Chromosomal aberration of part or all of X chromosome (45,X)
Prevalence of Turner X
1/2000
1/5000 females at birth
How many Turner-syndrome conceptions end in spontaneous abortion or still birth?
99%
Clinical features of Turner X?
Short Low hairline Low-set ears Broad chest Widely spaced nipples Webbed neck Obesity
Puberty in Turner X?
Ovarian failure before birth
Puberty does not occur naturally
Behavioural features of Turner X?
Hyperactivity and distractibility in childhood
Poor social skills & low self-esteem in adolescence
LD in Turner X?
Not typically
IQ in Turner X?
Normal intelligence
How many people with Turner X have VSD or coarctation of aorta?
12%
What is Triple X syndrome also known as?
Trisomy X
XXX
Genetics of Trisomy X
Presence of extra C chromosome in each cell of human female
Incidence of Triple X
1:1000 female births
How many people with Triple X have mild LD?
60-70%
Features of Triple X
Delayed language development
Motor coordination problems
Accelerated growth until puberty
Premature Ovarian failure
What psychiatric problems is Triple X associated with?
Anxiety
Increased incidence of schizophrenia
Other names for Klinefelters?
47,XXY
XXY
Incidence of Klinefelts
1:500 - 1:1000 live male births
Primary feature of Klinefelters
Sterility
Features of Klinefelters
Sparse body hair
Hypogonadism
Gynaecomastia
When does diagnosis of Klinefelters typically occur?
Puberty with variable degree of sexual characteristics
Height of those with Klinefelters?
Taller than average by 4cm
Thin build
Median IQ of Klinefelters
90
most in 60-70
Behavioural features of Klinefelters
Less introvertive & assertive
Less social
Poorer school performance
In which academic areas do Klinefelters do poorly?
Reading
Spelling
Genetics of XYY
Human male has extra Y chromosome
Another name of XYY
47, XYY
Incidence of XYY
1:1000 male births
IQ of XYY
Lower than average
Behavioural features of XYY
Associated with behavioural problems
Name some sex chromosome disorders
Fragile X
Turners
Klinefelters
XYY
Name some autosomal deletion and duplication disorders
Prader-Willi Angelmann Williams Cri-du-chat Smith-Magenis DiGeorge Rubinstein-Taybi
Genetics of Prader-Willi
Deletion or inexpression of 7 genes on chromosome 15q11-13 on paternal chromosome
M:F incidence of Prader-Willi
4:3
Incidence of Prader-Willi
1/10,000-1/25,000 live births
Early features of Prader-Willi
Hypotonia Lethargy Hypogonadism Breech/Caesarian Failure to thrive Excessive sleepiness Triangular mouth can cause feeding and swallowing problems
Childhood features of Prader-Willi
Increase in over-eating
Insatiable appetite can lead to stealing food
Sometimes consumption of unpalatable food
How many people with Prader-Willi have hyperphagia?
80%
Features of Prader-Willi in adulthood?
Obesity Hypotonia Infertility Hypogonadism Sparse pubic hair Extreme flexibility
IQ of Prader-Willi
<70 in 90%
Physical features of Prader-Willi
Prominent nasal bridge and forehead Small hands and feet Almond-shaped eyes Flattened face Thin upper lip Downturned mouth Lack of complete sexual development Striae Delayed motor development
How many people with Prader-Willi have autistic features
15%
Life expectancy of Prader-Willi
Dependent on obesity and associated physical health problems
Genetics of Angelmann
Deletion in 15q12 of maternal origin
How many people with Angelman have a deletion in maternally derived chromosome 15
80%
Prevalence of Angelman
1/20,000-1/30,000
Clinical features of Angelman
Happy disposition Paroxysmal laughter Hand flapping Clapping Ataxia
LD in Angelman
Severe/profound
Facial features of Angelman
Fair hair and blue eyes Microcephaly Flattened occiput Long face Prominent jaw Wide mouth Widely-spaced teeth Thin upper lip Pointed chin
How many people with Angelman have fair hair and blue eyes?
66%
How many people with Angelman have epilepsy?
90%
EEG changes in Angelman
Characteristic with changes noted as early as age 3
Genetic cause of Williams
Deletion of around 25 genes from long arm of chromosome 7
Prevalence of Williams
1/7500-20,000
Characteristic feature of Williams?
Elfin-like facial appearance
Infants with Williams?
Irritable Feeding problems Failure to thrive Developmental delay Growth retardation
How many children with Williams have high serum calcium levels?
> 60%
IQ in Williams?
40-80
Average 56
Features of Williams
Short, growth retardation
Premature wrinkling and sagging of skin
Hoarse voice
What physical problems are associated with Williams?
Renal and thyroid
Supravalvular aortic stenosis
Hypercalcaemia
Behavioural features of Williams?
Anxious, fearful Hypersensitive or outgoing Sociable Disinhibited Excessively friendly
What skills are often better in Williams?
Verbal better than motor or visuospatial
Genetics of Cri-du-chat
Partial deletion at 5p15.2
How many deletions in Cri-du-chat are spontaneous?
85%
Origin of majority of Cri-du-chat deletions?
Paternal
Incidence of Cri-du-chat
1/15,000-1/50,000
M:F ratio of Cri-du-chat
4:3
Characteristic feature of Cri-du-chat
Infant has high-pitched cry that resembles a cat
Characteristics of Cri-du-chat
Pronounced microcephaly Round face with hypertelorism Epicanthal folds Slanting palpebral fissues Broad flat nose Low-set ears Micrognathia Dental malocclusion
LD in Cri-du-chat?
Severe-profound
Behavioural features of Cri-du-chat
Hyperactivity in children
Stereotypies
Self-injury
Tantrums
Physical diseases associated with Cri-du-chat
Respiratory & ear infections
Congenital heart disease
GI abnormalities