Chromosomal abnormalities
DS and TS
Dr Moonga BScHb, MBcHB, PG-Dip, MSc-Resp, FZCMS Paeds
Benedictmga@gmail.com
Introduction
• A gene is the structural and functional unit of the inheritance.
• A Gene is responsible for the transmission of traits (eye colour, height
and many more) from the parents to the children.
• A gene is sequence of DNA that is is located at specific locations on
the Chromosomes
• There are 46 number of chromosomes in a normal human being that
is inherited from the parents.
• 23 number of chromosomes are inherited from the mother and 23
number of chromosomes are inherited from the father.
• the last 23rd chromosome is the sex chromosome that specify the
gender of the person. It can either be X or Y chromosome.
• A gene is present on a specific location on a chromosome.
• When a gene is expressed, it forms RNA that RNA then serve as a
template to produce Proteins that in turn produce biological actions
Genetic disorders
• Single gene disorders
• Autosomal dominant
• Autosomal recessive
• X-linked recessive
• X-linked Dominant
• Chromosomal disorders
• Multifactorial disorders
Type of chromosomal abnormalities
• Patau syndrome T13
• Edward syndrome T18
• Downs syndrome T21
• Tuner 23
• Cri du chat 5
T21
• Down syndrome is by far the most common and best known
chromosomal disorder in humans and the most common cause of
intellectual disability.
• It primarily results from trisomy of chromosome 21 which give rise to
multiple systemic complications as part of the syndrome.
• Levels of ability and challenges range widely in individuals with Down
syndrome. Some need significant support throughout life, while
others grow up to hold jobs and live on their own.
Clinical features
• Individuals with Down syndrome typically exhibit distinct dysmorphic
features
• primarily affecting the head, neck, and extremities. Cardiovascular
anomalies, particularly congenital heart defects are present in about
half of those with Down syndrome
• gastrointestinal issues such as duodenal atresia and esophageal
abnormalities are also prevalent.
Physical examination
• Flat occiput and a flattened facial appearance
• Small brachycephalic head
• Epicanthal folds
• Flat nasal bridge
• Upward-slanting palpebral fissure
• Small nose and small mouth
• Protruding tongue
• Small and dysplastic ears
• Generous nuchal skin
• Shortened extremities
• Short, broad hands with a short fifth finger (with hypoplasia of the
middle phalanx and clinodactyly), along with single transverse palmar
creases (~60% of patients)
• Joint hyperextensibility or hyperflexibility
• A wide space between the first and second toes (sandal gap)
• Neuromuscular hypotonia
• Dry skin
• Wide range of intelligence quotients (IQs)
• Heart defects
• The most common congenital heart defects are the following:
• Endocardial cushion defect (43%), which results in atrioventricular
septal defect
• Ventricular septal defect (32%)
• Secundum atrial septal defect (10%)
• Tetralogy of Fallot (6%)
• Isolated patent ductus arteriosus (4%)
• Central nervous system
• Behavior and psychiatric status
• Gastrointestinal tract abnormalities
• Genitourinary tract abnormalities
• Growth and skeletal anomalies
• Endocrine abnormalities
• Hematologic abnormalities
• Immunodeficiency
• Trisomy 21 mosaicism
Investigations
• Prenatal screening
• Postnatal screening
Management
• MDT
Tuners
• Turner syndrome is one of the more common chromosome anomalies
in humans
• It represents an important cause of short stature and ovarian
insufficiency in females.
• The true prevalence of Turner syndrome remains difficult to ascertain
because patients with a milder phenotype may remain undiagnosed.
Some individuals are not diagnosed until late adulthood if their
phenotype is mild.
• Turner syndrome is a sex chromosome disorder caused by loss of part
or all of an X chromosome
CLINICAL MANIFESTATIONS
Diagnosis
• Turner syndrome is occasionally diagnosed incidentally during
prenatal testing.
• The diagnosis is confirmed by karyotype analysis.
• Prompt diagnosis is important to permit management of
comorbidities, including effective treatment of short stature.
• Indications for testing A karyotype analysis for Turner syndrome
should be performed in any female with characteristic features, which
vary by age group
• Prenatal
• Newborn period
• Infants and children
• Adolescence
Diagnostic tests
• Standard karyotype analysis
• Newborn screening
• Other tests
Management
• MDT
• Growth hormone
• Cardiologist
• Nephrologist
• Psychologist
Thank you for listening
Dr Moonga
Benedictmga@gmail.com
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