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Chapter 31: Child Psychiatry
Cat’s Cry (Cri-du-Chat) Syndrome.
Children with cat’s
cry syndrome have a deletion in chromosome 5. They are typi-
cally severely intellectually disabled and show many signs often
associated with chromosomal aberrations, such as microceph-
aly, low-set ears, oblique palpebral fissures, hypertelorism, and
micrognathia. The characteristic cat-like cry that gave the syn-
drome its name is caused by laryngeal abnormalities that gradu-
ally change and disappear with increasing age.
Phenylketonuria.
PKU was first described by Ivar Asb-
jörn Fölling in 1934 as an inborn error of metabolism. PKU
is transmitted as a simple recessive autosomal Mendelian trait
and occurs in about 1 of every 10,000 to 15,000 live births. For
parents who have already had a child with PKU, the chance of
having another child with PKU is 20 to 25 percent of succes-
sive pregnancies. PKU is reported predominantly in persons
of North European origin; a few cases have been described in
blacks, Yemenite Jews, and Asians. The basic metabolic defect
in PKU is an inability to convert phenylalanine, an essential
amino acid, to paratyrosine because of the absence or inactiv-
ity of the liver enzyme phenylalanine hydroxylase, which cata-
lyzes the conversion. Therefore, PKU is largely preventable
with a screening for it, which, if positive, should be followed
with a low phenylalanine diet. Two other types of hyperphe-
nylalaninemia have recently been described. One is caused by
a deficiency of the enzyme dihydropteridine reductase, and the
other to a deficiency of a cofactor, biopterin. The first defect
can be detected in fibroblasts, and biopterin can be measured
in body fluids. Both these rare disorders carry a high risk of
fatality.
Most patients with PKU are severely intellectually disabled,
but some are reported to have borderline or normal intelligence.
Eczema, vomiting, and convulsions occur in about one third of
all patients. Although the clinical picture varies, typically, chil-
dren with PKU are reported to be hyperactive and irritable. They
frequently exhibit temper tantrums and often display bizarre
movements of their bodies and upper extremities, including
twisting hand mannerisms. Verbal and nonverbal communica-
tion is commonly severely impaired or nonexistent. The chil-
dren’s coordination is poor, and they have many perceptual
difficulties.
Currently, the Guthrie inhibition assay is a widely applied
screening test using a bacteriological procedure to detect phe-
nylalanine in the blood. In the United States, newborn infants
are routinely screened for PKU. Early diagnosis is important,
because a low-phenylalanine diet, in use since 1955, signifi-
cantly improves both behavior and developmental progress.
The best results seem to be obtained with early diagnosis and
the start of dietary treatment before the child is 6 months of
age. Dietary treatment, however, is not without risk. Phenylala-
nine is an essential amino acid, and its omission from the diet
can lead to such severe complications as anemia, hypoglyce-
mia, or edema. Dietary treatment of PKU should be continued
indefinitely. Children who receive a diagnosis before the age of
3 months and are placed on an optimal dietary regimen may
have normal intelligence. A low-phenylalanine diet does not
reverse intellectual disability in untreated older children and
adolescents with PKU, but the diet does decrease irritability
and abnormal electroencephalography (EEG) changes and does
increase social responsiveness and attention span. The parents
of children with PKU and some of the children’s normal siblings
are heterozygous carriers.
Rett syndrome.
Rett syndrome, now diagnosed in the
DSM-5 as a form of autism spectrum disorder, is believed to
be caused by a dominant X-linked gene. It is degenerative and
affects only females. In 1966, Andreas Rett reported on 22 girls
with a serious progressive neurological disability. Deterioration
in communications skills, motor behavior, and social function-
ing starts at about 1 year of age. Symptoms include ataxia, facial
grimacing, teeth-grinding, and loss of speech. Intermittent
hyperventilation and a disorganized breathing pattern are char-
acteristic while the child is awake. Stereotypical hand move-
ments, including hand-wringing, are typical. Progressive gait
disturbance, scoliosis, and seizures occur. Severe spasticity is
usually present by middle childhood. Cerebral atrophy occurs
with decreased pigmentation of the substantia nigra, which sug-
gests abnormalities of the dopaminergic nigrostriatal system.
Neurofibromatosis.
Also called
von Recklinghausen’s
,
neurofibromatosis is the most common of the neurocutaneous
syndromes caused by a single dominant gene, which may be
inherited or occur as a new mutation. The disorder occurs in
about 1 of 5,000 births and is characterized by café au lait spots
on the skin and by neurofibromas, including optic gliomas and
acoustic neuromas, caused by abnormal cell migration. Mild
intellectual disability occurs in up to one third of those with
the disease.
Tuberous Sclerosis.
Tuberous sclerosis is the second most
common of the neurocutaneous syndromes; a progressive intel-
lectual disability occurs in up to two thirds of all affected per-
sons. It occurs in about 1 of 15,000 persons and is inherited
by autosomal dominant transmission. Seizures are present in all
those with intellectual disability, and in two thirds of those who
are not. Infantile spasms may occur as early as 6 months of age.
The phenotypic presentation includes adenoma sebaceum and
ash-leaf spots that can be identified with a slit lamp.
Lesch-Nyhan Syndrome.
Lesch-Nyhan syndrome is
a rare disorder caused by a deficiency of an enzyme involved
in purine metabolism. The disorder is X-linked; patients have
intellectual disability, microcephaly, seizures, choreoathetosis,
and spasticity. The syndrome is also associated with severe
compulsive self-mutilation by biting the mouth and fingers.
Lesch-Nyhan syndrome is another example of a genetically
determined syndrome with a specific, predictable behavioral
pattern.
Adrenoleukodystrophy
The most common of several disorders of sudanophilic cere-
bral sclerosis, adrenoleukodystrophy is characterized by dif-
fuse demyelination of the cerebral white matter resulting in
visual and intellectual impairment, seizures, spasticity, and
progression to death. The cerebral degeneration in adrenoleu-
kodystrophy is accompanied by adrenocortical insufficiency.
The disorder is transmitted by a sex-linked gene located on the
distal end of the long arm of the X chromosome. The clinical
onset is generally between 5 and 8 years of age, with early
