Questions and Answers
What is the primary cause of trisomy 21 in Down syndrome cases?
Which of the following cytogenetic abnormalities can cause Down syndrome?
In which stage of meiosis does non-disjunction occur more frequently leading to trisomy 21?
What is the result of non-disjunction during oogenesis?
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What critical maternal factor is believed to contribute to the increase in trisomy 21 risk with age?
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How is Down syndrome typically diagnosed at birth?
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What is the consequence of the extra chromosome 21 in Down syndrome as the embryo grows?
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Which factor is least associated with the risk of trisomy 21?
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What is another name for Down syndrome?
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What percentage of Down syndrome cases account for moderate and severe mental handicaps in school-aged children?
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What is the mean IQ value typically associated with individuals with Down syndrome?
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Which of the following is the only well-established risk factor for Down syndrome?
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At what maternal age does the risk of having a child with Down syndrome increase significantly?
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What characteristic is NOT typically associated with Down syndrome?
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Which statement about the prevalence of Down syndrome is correct?
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Who was Down syndrome named after?
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Which of the following characteristics is commonly found in children with Down syndrome?
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What is the term for the condition characterized by a high tongue that often protrudes in children with Down syndrome?
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Which of these facial features is typically associated with Down syndrome?
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In a karyotype analysis, what chromosomal abnormality is most commonly linked to Down syndrome?
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What is the common term for the increased distance between the eyes often seen in children with Down syndrome?
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What is a common hearing condition found in children with Down syndrome?
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What is the appearance of the back of the head in many children with Down syndrome?
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What characteristic of the ears is frequently observed in individuals with Down syndrome?
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What is the primary purpose of screening tests for Down syndrome (DS) during pregnancy?
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Which diagnostic test involves sampling cells from the placenta?
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What is the accuracy rate of chorionic villus sampling (CVS) for detecting Down syndrome?
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What is a common risk associated with chorionic villus sampling (CVS)?
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Which intervention is considered imperative for managing gastrointestinal anomalies in newborns?
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Why is timely surgery necessary for cardiac malformations in infants?
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What is a key focus of early intervention programs for infants aged 0–3 years?
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What condition may necessitate surgical removal of enlarged adenoids in patients?
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Study Notes
Overview of Down Syndrome
- Down syndrome (DS), also known as trisomy 21, is caused by an extra chromosome 21.
- Characterized by low intelligence, distinct facial features, and various physical development delays.
- Severity ranges from mild to severe, impacting life quality.
Significance of Down Syndrome
- Trisomy 21 is the most common chromosomal abnormality affecting non-sex chromosomes.
- It is the leading cause of birth defects and accounts for one-third of moderate to severe mental handicaps in children.
- Average IQ in individuals with DS ranges between 20-85, with a mean around 50.
- Advanced maternal age is a recognized risk factor, particularly for women over 35, although 80% of children with DS are born to younger mothers.
- Maternal origin accounts for 95% of trisomy 21 cases; some studies indicate advanced paternal age may also be a factor.
Pathophysiology
- DS can arise from three cytogenetic anomalies: trisomy 21, translocation, and mosaicism.
- Non-disjunction during cell division leads to an uneven number of chromosomes, typically 45 or 47.
- Non-disjunction events are more frequent during the first meiotic division.
- The connection between advanced maternal age and nondisjunction remains unclear, hypothesized to relate to the age of maternal egg cells.
Diagnosis and Clinical Manifestations
- Diagnosis often occurs at birth or shortly after, based on physical features unique to DS.
- Common characteristics include hypotonia (poor muscle tone), simian crease (single palm crease), somewhat flattened facial profile, and upward slanting eyes.
- Additional features may include:
- Sloping forehead, broad flat nasal bridge, and epicanthal folds.
- Hypertelorism (increased distance between eyes) and Brushfield spots (white spots around the iris).
- Microcephaly (small head) and abnormal head shape.
- Macroglossia (large, protruding tongue) and small, low-set ears.
- Brachydactyly (broad hands with short fingers) and hyperextensible joints.
- Hearing abnormalities are common, with 66% of children affected.
Diagnostic Tests
- Definitive diagnosis confirmed through karyotyping, which provides a visual display of chromosomes.
- Majority of DS cases are simple trisomy 21; however, translocations may indicate hereditary risks.
- Prenatal diagnostic options include:
- Chorionic villus sampling (CVS), performed between 10-13 weeks gestation; has a miscarriage risk of 1 in 100 and accuracy over 95%.
- Amniocentesis, which samples amniotic fluid.
Management and Treatment
- Immediate treatment may be necessary for respiratory and ear infections.
- Cardiac malformations often require surgery before six months of age.
- Gastrointestinal anomalies and obstructive sleep apnea may necessitate surgical interventions.
- Early intervention programs targeting infants (0-3 years) emphasize language, motor development, and social skills to enhance development outcomes.
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Description
This quiz explores Down syndrome, also known as trisomy 21, focusing on its characteristics, causes, and varying severity. Learn about the impact of chromosome 21 abnormalities on physical development and intelligence. Test your understanding of this condition's multifaceted nature.
