Podcast
Questions and Answers
An 11-year-old female presents with a high-pitched cry, microcephaly, and hypotonia. A genetic test reveals a deletion on the short arm of chromosome 5. Which of the following molecular mechanisms is most directly responsible for the observed phenotype in this condition?
An 11-year-old female presents with a high-pitched cry, microcephaly, and hypotonia. A genetic test reveals a deletion on the short arm of chromosome 5. Which of the following molecular mechanisms is most directly responsible for the observed phenotype in this condition?
- Trisomy of chromosome 21, leading to an overall increase in gene dosage and altered developmental pathways.
- Unstable trinucleotide repeat expansions within the FMR1 gene, causing silencing and loss of function.
- Haploinsufficiency of multiple genes due to chromosomal deletion. (correct)
- Point mutations in the TBX1 gene, disrupting pharyngeal pouch development.
An infant is born with a ventricular septal defect, parathyroid hypoplasia, and thymic aplasia. Which of the following sets of clinical findings would be most indicative of DiGeorge syndrome rather than a phenotypically similar condition?
An infant is born with a ventricular septal defect, parathyroid hypoplasia, and thymic aplasia. Which of the following sets of clinical findings would be most indicative of DiGeorge syndrome rather than a phenotypically similar condition?
- Elevated serum calcium, normal T-cell counts, and presence of epicanthal folds.
- Normal serum calcium, decreased T-cell counts, and a long face with large ears.
- Hypocalcemia, normal T-cell counts, and macroorchidism after puberty.
- Hypocalcemia, decreased T-cell counts, and a microdeletion at 22q11.2. (correct)
An 11-year-old male is diagnosed with DiGeorge syndrome. Considering the embryological development, which of the following developmental processes is most likely disrupted due to the 22q11.2 deletion?
An 11-year-old male is diagnosed with DiGeorge syndrome. Considering the embryological development, which of the following developmental processes is most likely disrupted due to the 22q11.2 deletion?
- Neural tube closure during the first trimester.
- Formation of the pharyngeal pouches. (correct)
- Development of the notochord.
- Differentiation of hematopoietic stem cells in the bone marrow.
A child presents with hypotonia, developmental delay, and a high-pitched cry. Cytogenetic analysis reveals a deletion of the 5p chromosome region. Which of the following long-term complications is this child most at risk of developing, considering the underlying genetic defect?
A child presents with hypotonia, developmental delay, and a high-pitched cry. Cytogenetic analysis reveals a deletion of the 5p chromosome region. Which of the following long-term complications is this child most at risk of developing, considering the underlying genetic defect?
An infant is suspected to have DiGeorge syndrome. Which of the following investigations would be the most appropriate initial step in confirming the diagnosis, considering the variable clinical presentation of the condition?
An infant is suspected to have DiGeorge syndrome. Which of the following investigations would be the most appropriate initial step in confirming the diagnosis, considering the variable clinical presentation of the condition?
An 11-year-old female is diagnosed with Cri du Chat syndrome following genetic testing. Her parents express concern about recurrence risk in future pregnancies. What is the most accurate counseling regarding the risk of recurrence?
An 11-year-old female is diagnosed with Cri du Chat syndrome following genetic testing. Her parents express concern about recurrence risk in future pregnancies. What is the most accurate counseling regarding the risk of recurrence?
A newborn presents with a high-pitched cry and facial dysmorphisms suggestive of Cri du Chat syndrome. Which of the following findings on a laryngeal examination would best explain the characteristic cry in this condition?
A newborn presents with a high-pitched cry and facial dysmorphisms suggestive of Cri du Chat syndrome. Which of the following findings on a laryngeal examination would best explain the characteristic cry in this condition?
A child with confirmed DiGeorge syndrome is found to have severely reduced T-lymphocyte counts. Which of the following immunological mechanisms is most likely impaired, leading to the increased susceptibility to infections?
A child with confirmed DiGeorge syndrome is found to have severely reduced T-lymphocyte counts. Which of the following immunological mechanisms is most likely impaired, leading to the increased susceptibility to infections?
An 11-year-old male with DiGeorge syndrome requires surgical correction of a congenital heart defect. What specific precaution should be taken during the perioperative period, given the underlying pathophysiology of his condition?
An 11-year-old male with DiGeorge syndrome requires surgical correction of a congenital heart defect. What specific precaution should be taken during the perioperative period, given the underlying pathophysiology of his condition?
A researcher is investigating the genetic basis of DiGeorge syndrome. Which of the following experimental approaches would be most effective in identifying novel genes within the 22q11.2 deletion region that contribute to the variable expressivity of the syndrome?
A researcher is investigating the genetic basis of DiGeorge syndrome. Which of the following experimental approaches would be most effective in identifying novel genes within the 22q11.2 deletion region that contribute to the variable expressivity of the syndrome?
Flashcards
Cri du Chat Syndrome
Cri du Chat Syndrome
A genetic disorder caused by a microdeletion of the short arm of chromosome 5.
High-Pitched Cry
High-Pitched Cry
A high-pitched cry resembling a cat's meow, a hallmark symptom of Cri du Chat syndrome.
Microcephaly
Microcephaly
Smaller than average head circumference, often seen in Cri du Chat syndrome.
Hypertelorism
Hypertelorism
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DiGeorge Syndrome
DiGeorge Syndrome
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Hypocalcemia
Hypocalcemia
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Thymic Hypoplasia
Thymic Hypoplasia
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Ventricular Septal Defect (VSD)
Ventricular Septal Defect (VSD)
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CATCH 22
CATCH 22
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TBX1 gene
TBX1 gene
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Study Notes
- Two distinct genetic disorders in pediatric patients need to be differentiated
- These disorders must be diagnosed based on clinical and genetic findings
Case 1: Cri du Chat Syndrome (5p Deletion Syndrome)
- 11-year-old female presents with developmental delays
- Her mother experienced antenatal bleeding and oligohydramnios during pregnancy
- The patient was born prematurely via C-section with low birth weight (2.2 kg)
- The patient presents symptoms like sucking difficulties and a high-pitched cry
- The patient also has delayed motor milestones (neck control at 8-9 months) and limited speech
- Physical examination reveals microcephaly, hypertelorism, low-set ears, pes planus, and hypotonia
- Behavioral issues include temper tantrums and self-injurious behavior
- Has absent verbal communication
- This syndrome is caused by a microdeletion on the short arm of chromosome 5 (5p-)
- A key diagnostic feature is a high-pitched cry resembling a cat
- Other features include microcephaly, hypertelorism, facial anomalies, congenital heart defects, moderate to severe intellectual disability, hypotonia, and epicanthal folds
- Down syndrome should be considered in the differential diagnosis due to overlapping features
- Karyotype or FISH analysis can confirm the 5p deletion
Case 2: DiGeorge Syndrome (22q11.2 Deletion Syndrome)
- 11-year-old male presents with seizures and delayed milestones
- Physical examination reveals a coarse facial appearance with small ears, a narrow forehead, and a long face
- Cardiac auscultation indicates a holosystolic murmur
- Lab findings include hypocalcemia and low parathyroid hormone (PTH) levels
- Urine calcium is elevated
- The patient also has a ventricular septal defect (VSD) confirmed by echocardiography
- DiGeorge Syndrome is caused by a microdeletion on chromosome 22 (22q11.2 deletion)
- The TBX1 gene is affected, which plays a role in pharyngeal pouch development
- Clinical features include parathyroid hypoplasia (leading to hypocalcemia), thymic aplasia/hypoplasia (leading to immunodeficiency), facial anomalies (cleft palate, long face, broad nose, small ears), and congenital heart conditions (VSD, Tetralogy of Fallot)
- The mnemonic CATCH 22 is useful for remembering key features: Cardiac defects, Abnormal facies, Thymic hypoplasia, Cleft palate, Hypocalcemia, and chromosome 22 deletion
- Diagnosis is confirmed by FISH or karyotype analysis
Additional Information
- Fragile X Syndrome and Klinefelter Syndrome can present with a long face
- A genetic testing will be required for diagnosis
Summary
- Cri du Chat Syndrome exhibits a high-pitched cry, microcephaly, hypertelorism, hypotonia, intellectual disability, and potential heart defects
- DiGeorge Syndrome is characterized by hypocalcemia, thymic hypoplasia, facial anomalies, and congenital heart defects
- Genetic testing is essential to confirm both diagnoses
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