Intellectual impairment Flashcards
Which of the following is not a criterion for
intellectual disability?
A. Deficits in intellectual functioning (reasoning, problem solving, planning, abstract, judgement, academic learning) confirmed by clinical and standardised intelligence testing
B. Severe verbal learning delays
C. Deficits in adaptive function resulting in failure to meet developmental/sociocultural standards for personal independence/social responsibility (conceptual, social, practical)
D. Onset during developmental period
E. All of the above
B
A decline in IQ begins at approximately 10 to 15 years in which of the following disorders? A. Down syndrome B. Fragile X syndrome C. Cerebral palsy D. Nonspecific mental retardation E. Fetal alcohol syndrome
The answer is B
Children with Down syndrome show their highest IQ scores during the first year
of life and then decline in IQ over the early to middle childhood years. Boys
with fragile X syndrome also decline in IQ, but their declines seem to begin at
approximately 10 to 15 years of age. Conversely, children with cerebral palsy
(half of whom have mental retardation) remain remarkably stable in their IQ
scores over time, similar to groups with mixed or nonspecific etiologies of
mental retardation.
Which of the following disorders is least often associated with fragile X
syndrome?
A. Autistic disorder
B. Schizotypal personality disorder
C. Attention-deficit/hyperactivity disorder
D. Bipolar disorder
E. Social anxiety disorder
D
The answer is D
Fragile X syndrome is associated with shyness, gaze aversion, and social
difficulties. A number of psychiatric diagnoses commonly co-occur with fragile
X, including autistic disorder, schizotypal personality disorder, attention-deficit/hyperactivity
disorder, and social anxiety disorder. These difficulties vary in severity in
this population and are found in individuals with fragile X syndrome across the
IQ spectrum, from those with moderate mental retardation to those with mild
learning disabilities. Bipolar disorder is less commonly associated with fragile
X syndrome than these other disorders.
Among all known causes of mental retardation, which of the following
syndromes is least associated with comorbid Axis I psychiatric disorder?
A. Down syndrome
B. Fragile X syndrome
C. Nonspecific type
D. Fetal alcohol syndrome
E. Prader-Willi syndrome
A
The answer is A
Compared with other individuals with mental retardation, persons with Down
syndrome appear to suffer less often and less severely from psychopathology.
Rates of psychiatric disorders in children and adolescents with Down syndrome
exceed those in the general population but are significantly lower than in
persons with mental retardation caused by other etiologies, such as fragile X
syndrome, fetal alcohol syndrome, Prader-Willi syndrome, and nonspecific type.
Commonly noted psychiatric problems among individuals with mental retardation
include attention problems, impulsivity, hyperactivity, and aggression. In
contrast to these problems, depression seems to be less common in persons with
mental retardation than in the general population
A microdeletion on chromosome 7 is the primary cause of A. Prader-Willi syndrome B. fragile X syndrome C. Williams' syndrome D. Rett syndrome E. none of the above
The answer is C
Williams’ syndrome is caused by a microdeletion of the gene responsible for the
body’s production of elastin, a protein that provides strength and elasticity to
vital tissues of the body (e.g., blood vessels and lungs). This gene is located
on chromosome 7. Persons with Williams’ syndrome often show hyperacusis,
hypercalcemia, neuromusculoskeletal and renal abnormalities, and cardiovascular
disease (especially supravalvular aoritic stenosis). Characteristic facial
features are described as elfin-like, cute and appealing
Only known human disease that is affected by genomic imprinting
Prader-Willi syndrome is the only known human disease that is affected by
genomic imprinting, in which genes are modified and expressed differently
depending on whether the mutation, which occurs on chromosome 15, is inherited
from the mother or the father.
Xsomal abnormality in Fragile X syndrome
Fragile X syndrome is the most common inherited form of mental retardation.
Fragile X syndrome occurs when the fmr1p (or fragile X gene) becomes methylated
as a result of amplification (repetition) of the trinucleotide sequences (CGG)
that make up DNA.
Xsomal abnormality in Rett syndrome
Can boys have Rett syndrome?
Rett syndrome is caused by mutations in the gene MECP2 located on the X
chromosome and can arise (1) sporadically or (2) from germline mutations. Rett
syndrome is exclusively a female disorder becaus`male fetuses with this
syndrome rarely survive to term, and those who do die shortly after birth. Males
cannot survive with Rett syndrome because they lack the second X chromosome,
which in females compensates for the damage to the other X chromosome.
All of the following chromosomal aberrations associated with Down syndrome
lead to a phenotypic expression of the disorder except
A. patients have 45 chromosomes
B. patients have three copies of chromosome 21
C. patients have 47 chromosomes
D. patients have 46 chromosomes, but two, usually 15 and 21, are fused
E. patients have mosaicism, with normal and trisomic cells in various tissuese
The answer is A
Three types of chromosomal aberrations are recognized in Down syndrome. First,
patients with trisomy 21 (three copies of chromosome 21 rather than the usual
two) represent the overwhelming majority of individuals with Down syndrome. They
have 47 chromosomes with an extra copy of 21. The mother’s karyotypes are
normal. A nondisjunction during meiosis is responsible for the trisomy.
Second, nondisjunction occurring after fertilization in any cell division
results in mosaicism, with both normal and trisomic cells found in various
tissues.
Third, in translocations, there is a fusion of two chromosomes, usually 15 and
21, resulting in a total of 46 chromosomes, despite the presence of an extra
chromosome 21. This version of the disorder, unlike trisomy 21, is usually
inherited, and the translocated chromosome may be found in unaffected parents
and siblings, who would have only 45 chromosomes.
The genetic finding most closely linked to advancing maternal age is
A. translocation between chromosomes 14 and 21
B. mitotic nondisjunction of chromosome 21
C. partially trisomic karyotype
D. meiotic nondisjunction of chromosome 21
E. all of the above
The answer is D
Meiotic nondisjunction of chromosome 21 produces approximately 85 percent of
cases of Down syndrome and has been most closely linked to advancing maternal
age. Paternal age has also been implicated as a factor in some studies.
Translocation events constitute only 5 percent of Down syndrome cases. In cases
in which an asymptomatic parent carries the aberrant chromosome in his or her
genome, subsequent Down syndrome in an offspring is unrelated to parental age.
If the translocation occurs between chromosomes 14 and 21, the proband carries
46 chromosomes, including two normal 21 chromosomes; one normal 14 chromosome;
and the 14/21 translocation, which carries parts of both chromosomes. Any
asymptomatic parent or sibling who is a carrier of the translocation has only 45
chromosomes, with one 21 chromosome missing, and is thus spared the excessive
genetic complement.
Mitotic nondisjunction of chromosome 21, which occurs in 1 percent of all Down
syndrome cases, occurs after fertilization of a presumably healthy ovum and may
therefore be considered independent of maternal age. Partially trisomic
karyotype may refer to the mosaicism-some cells normal, others with trisomy
21-seen in mitotic nondisjunction or to the excessive complement of chromosome
21 produced by translocation. Neither case is as closely tied to maternal age as
is meiotic nondisjunction.
Which of the following chromosomal abnormalities is most likely to cause
mental retardation?
A. Extra chromosome 21 (trisomy 21)
B. Fusion of chromosomes 21 and 15
C. XO (Turner’s syndrome)
D. XXY (Klinefelter’s syndrome)
E. XXYY and XXXY (Klinefelter’s syndrome variants)
The answer is A
An extra chromosome 21 is the most common genetic abnormality found in Down
syndrome, and the abnormality most likely to cause mental retardation.
Abnormalities in autosomal chromosomes are, in general, associated with mental
retardation. The chromosomal aberration represented by 46 chromosomes with
fusion of 15 and 21 produces a type of Down syndrome that, unlike trisomy 21, is
usually inherited. Aberrations in sex chromosomes are not always associated with
mental retardation, such as in XO (Turner’s syndrome), XXY (Klinefelter’s
syndrome), and XXYY and XXXY (Klinefelter’s syndrome variants) genotypes. Some
children with Turner’s syndrome have normal to superior intelligence.
Girls with Turner’s syndrome have gonadal agenesis and do not develop secondary
sexual characteristics without medical intervention. Another hallmark feature is
a webbed neck. In Klinefelter’s syndrome and its variants, individuals have
underdeveloped male genitalia and infertility and may develop gynecomastia
beginning in adolescence.
Characteristic facial features and high degree of social responsiveness in Downs Syndrome
characteristic facial features
(epicanthal folds, flattened nasal bridge) and high degree of social responsiveness
of Down syndrome. In the overwhelming majority of cases, the etiology of Down
syndrome is an abnormality of chromosome 21, known as trisomy 21.
The physical phenotype shown in Figure 37.2, including long facial
contour, large anteverted ears, and macro-orchidism (not shown) in this young
adult with mental retardation is consistent with which of the following
diagnoses?
A. Prader-Willi syndrome
B. Down syndrome
C. Klinefelter’s syndrome
D. Fetal alcohol syndrome
E. Fragile X syndrome
The answer is E
Figure 37.2 shows a young adult with fragile X syndrome, the second most common
single cause of mental retardation (after trisomy 21, the predominant form of
Down syndrome) and the leading inherited cause of mental retardation. The
physical phenotype of Down syndrome includes epicanthal folds; high cheekbones;
a protruding tongue; a single transverse palmar crease; and a number of other
associated features, including congenital heart defects and gastrointestinal
malformations. Prader-Willi syndrome, caused by a microdeletion on chromosome
15, is characterized by mental retardation, hyperphagia, obesity, hypogonadism,
and short stature. Fetal alcohol syndrome consists of mental retardation and a
typical phenotypic picture of facial dysmorphism, including hypertelorism,
microcephaly, short palpebral fissures, a smooth philtrum, and a thin upper lip.
Klinefelter’s syndrome is a condition caused by XXY genotype, characterized by
male habitus with hypogonadism because of low androgen production
A. Prader-Willi syndrome
B. Down syndrome
C. Fragile X syndrome
D. Phenylketonuria (PKU)
Attributed to a deletion in chromosome 15
A
A. Prader-Willi syndrome
B. Down syndrome
C. Fragile X syndrome
D. Phenylketonuria (PKU)
Most commonly occurs via autosomal recessive transmission
D
Phenylketonuria (PKU) is transmitted via autosomal recessive
inheritance of a defect found on chromosome 12, and it occurs in one in 10,000
births. The defect transmitted is an inability to convert phenylalanine, an
essential amino acid, to paratyrosine because of an absence or inactivity of the
liver enzyme phenylalanine hydroxylase. The majority of patients with PKU are
severely retarded, but some have borderline or normal intelligence. Eczema,
hypopigmented hair and eyes, and seizures are other common symptoms. Early
detection is crucial because a low-phenylalanine diet significantly improves
both cognitive development and behavior
A. Prader-Willi syndrome
B. Down syndrome
C. Fragile X syndrome
D. Phenylketonuria (PKU)
Abnormalities involving chromosome 21
B
A. Prader-Willi syndrome
B. Down syndrome
C. Fragile X syndrome
D. Phenylketonuria (PKU)
Occurs via a chromosomal mutation at Xq27.3
C
Fragile X syndrome is the second most common single cause of mental retardation,
and it results from a mutation on the X chromosome at the fragile site Xq27.3.
There is much variation in both the genetic and phenotypic expression.
Prevalence rates are one per 1,000 males and one per 2,000 females, but rates of
fully affected individuals are likely closer to one per 4,000 males and one per
8,000 females. Behaviorally, those with fragile X syndrome often have attention
problems, pervasive developmental disorders, and other learning disorders.
Intellectual function may deteriorate in adolescence in individuals with fragile
X syndrome.
A. Prader-Willi syndrome
B. Down syndrome
C. Fragile X syndrome
D. Phenylketonuria (PKU)
Example of a genomic imprinting
A
Prader-Willi syndrome results from a microdeletion in chromosome 15 and usually
occurs sporadically, with prevalence of less than one in 10,000. Its clinical
manifestations include compulsive eating behaviors, obesity, mental retardation,
hypogonadism, hypotonia, and short stature. Disruptive behaviors, including
oppositional and defiant behavior with frequent temper tantrums, are also
common. Prader-Willi provides an example of genomic imprinting, the process
whereby specific genes are differentially marked during parental gametogenesis,
resulting in differential expression in the individual; Prader-Willi syndrome
results when the microdeletion of chromosome 15 occurs in the chromosome
inherited from the father. Angelman syndrome, a clinically distinct entity,
occurs when the deletion occurs in the chromosome inherited from the mother.
A. Trisomy 21
B. Autosomal dominant
C. Autosomal recessive
D. X-linked semidominant
Neurofibromatosis
B
Neurofibromatosis manifests as neurofibromas, cafe-au-lait spots, seizures,
optic and acoustic gliomas, and bone lesions. Its transmission is autosomal
dominant.
A. Trisomy 21
B. Autosomal dominant
C. Autosomal recessive
D. X-linked semidominant
Tuberous sclerosis
B
Tuberous sclerosis presents with seizures, intracranial calcifications,
pink-brown skins lesions, and bone lesions. Transmission is autosomal dominant
A. Trisomy 21
B. Autosomal dominant
C. Autosomal recessive
D. X-linked semidominant
Crouzon’s syndrome
B
Crouzon’s syndrome, also known as craniofacial dysostosis, is manifested by
proptosis with shallow orbits, maxillary hypoplasia, and craniosynostosis. Its
transmission is autosomal dominant
A. Trisomy 21
B. Autosomal dominant
C. Autosomal recessive
D. X-linked semidominant
Cockayne’s syndrome
C
Cockayne’s syndrome presents with hypotrichosis, photosensitivity, thin skin,
diminished subcutaneous fat, and impaired hearing. Craniofacial findings include
pinched facies, sunken eyes, a thin nose, prognathism, and retinal degeneration.
Skeletal abnormalities include long limbs with large hands and feet and flexion
deformities. Transmission is autosomal recessive
A. Adrenoleukodystrophy
B. Rett syndrome
C. Acquired immune deficiency syndrome (AIDS)
D. Rubella
E. Cytomegalic inclusion disease/cytomegalic virus (CMV)
F. Toxoplasmosis
Mental retardation with periventricular intracerebral calcifications,
jaundice, microcephaly, and hepatosplenomegaly
E
A. Adrenoleukodystrophy
B. Rett syndrome
C. Acquired immune deficiency syndrome (AIDS)
D. Rubella
E. Cytomegalic inclusion disease/cytomegalic virus (CMV)
F. Toxoplasmosis
Progressive encephalopathy and mental retardation in 50 percent of
children born to mothers with this disorder
C
A. Adrenoleukodystrophy
B. Rett syndrome
C. Acquired immune deficiency syndrome (AIDS)
D. Rubella
E. Cytomegalic inclusion disease/cytomegalic virus (CMV)
F. Toxoplasmosis
An X-linked mental retardation syndrome that is degenerative and affects
only females
View Answer37.23
B
