Podcast
Questions and Answers
A couple attends their 20-week prenatal appointment. The quadruple screen results show decreased levels of AFP, estriol, and HCG, with inhibin A being within the normal range. Considering these results, which of the following conditions is MOST likely?
A couple attends their 20-week prenatal appointment. The quadruple screen results show decreased levels of AFP, estriol, and HCG, with inhibin A being within the normal range. Considering these results, which of the following conditions is MOST likely?
- Turner Syndrome (Monosomy X) where hormone levels would be unaffected.
- Trisomy 21 (Down Syndrome), where inhibin A is typically elevated.
- Trisomy 13 (Patau Syndrome) where second trimester screening is normal.
- Trisomy 18 (Edwards Syndrome), characterized by decreased AFP, estriol, and HCG with variable inhibin A. (correct)
During an autopsy of a stillborn fetus, the pathologist notes several anomalies, including dolichocephaly, micrognathia, overlapping fingers, and rocker-bottom feet. Karyotype analysis reveals trisomy 18. Which of the following underlying mechanisms BEST explains the combination of these findings?
During an autopsy of a stillborn fetus, the pathologist notes several anomalies, including dolichocephaly, micrognathia, overlapping fingers, and rocker-bottom feet. Karyotype analysis reveals trisomy 18. Which of the following underlying mechanisms BEST explains the combination of these findings?
- A mutation affecting ribosome biogenesis leading to skeletal and craniofacial abnormalities.
- Maternal autoantibodies interfering with normal connective tissue formation and skeletal development.
- Non-disjunction during meiosis affecting chromosome segregation, resulting in multiple organ system defects. (correct)
- A homeobox gene mutation disrupting the anterior-posterior axis determination during development.
A 38-year-old pregnant woman undergoes amniocentesis at 16 weeks gestation due to advanced maternal age. The karyotype reveals trisomy 18 in some cells but not others. Which of the following genetic phenomena BEST explains this finding?
A 38-year-old pregnant woman undergoes amniocentesis at 16 weeks gestation due to advanced maternal age. The karyotype reveals trisomy 18 in some cells but not others. Which of the following genetic phenomena BEST explains this finding?
- Uniparental disomy, resulting in differential gene expression.
- Mosaicism, where some cells have the trisomy and others are normal due to post-zygotic chromosomal loss or non-disjunction. (correct)
- Robertsonian translocation, leading to variable expression of the trisomy.
- Germline mosaicism in the mother, causing incomplete penetrance of the trisomy.
A neonate is born with several congenital anomalies, including a prominent occiput, low-set ears, and cardiac defects. The infant also exhibits clenched fists with overlapping fingers. Considering these clinical features, which of the following conditions is the MOST likely diagnosis?
A neonate is born with several congenital anomalies, including a prominent occiput, low-set ears, and cardiac defects. The infant also exhibits clenched fists with overlapping fingers. Considering these clinical features, which of the following conditions is the MOST likely diagnosis?
A newborn presents with overlapping fingers, rocker-bottom feet, and a VSD (ventricular septal defect). Suspecting a chromosomal abnormality, which of the following would be the MOST appropriate next step in confirming the diagnosis?
A newborn presents with overlapping fingers, rocker-bottom feet, and a VSD (ventricular septal defect). Suspecting a chromosomal abnormality, which of the following would be the MOST appropriate next step in confirming the diagnosis?
A fetus is diagnosed with Edward syndrome based on prenatal ultrasound findings and confirmed by chorionic villus sampling (CVS). The parents are considering the prognosis and long-term care. Which of the following is the MOST accurate statement regarding the prognosis for infants with Edward syndrome?
A fetus is diagnosed with Edward syndrome based on prenatal ultrasound findings and confirmed by chorionic villus sampling (CVS). The parents are considering the prognosis and long-term care. Which of the following is the MOST accurate statement regarding the prognosis for infants with Edward syndrome?
A 39-year-old woman is pregnant with her first child. Her first-trimester screening reveals decreased levels of pregnancy-associated plasma protein A (PAPP-A) and human chorionic gonadotropin (hCG). Which of the following conditions is MOST closely associated with this pattern of results?
A 39-year-old woman is pregnant with her first child. Her first-trimester screening reveals decreased levels of pregnancy-associated plasma protein A (PAPP-A) and human chorionic gonadotropin (hCG). Which of the following conditions is MOST closely associated with this pattern of results?
During a genetic counseling session, the parents of a child diagnosed with Edwards syndrome ask about the recurrence risk in future pregnancies. What is the MOST accurate explanation of the recurrence risk?
During a genetic counseling session, the parents of a child diagnosed with Edwards syndrome ask about the recurrence risk in future pregnancies. What is the MOST accurate explanation of the recurrence risk?
What specific findings on a fetal ultrasound would raise suspicion for Edward's syndrome in the second trimester, prompting further diagnostic testing?
What specific findings on a fetal ultrasound would raise suspicion for Edward's syndrome in the second trimester, prompting further diagnostic testing?
A researcher is investigating the epigenetic modifications associated with Edwards syndrome. Which of the following mechanisms is MOST likely to be implicated in the pathophysiology of this condition?
A researcher is investigating the epigenetic modifications associated with Edwards syndrome. Which of the following mechanisms is MOST likely to be implicated in the pathophysiology of this condition?
Flashcards
Edward Syndrome
Edward Syndrome
Trisomy of chromosome 18; three copies of chromosome 18 instead of the usual two.
Genetic Basis of Trisomies
Genetic Basis of Trisomies
Most common cause is increased maternal age (>35 years) and nondisjunction during meiosis I or II.
Dolichocephaly
Dolichocephaly
Elongated head shape from front to back.
Horseshoe Kidney
Horseshoe Kidney
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Polyhydramnios
Polyhydramnios
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Pulmonary Hypoplasia
Pulmonary Hypoplasia
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Overlapping Fingers
Overlapping Fingers
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Rocker Bottom Feet
Rocker Bottom Feet
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Quadruple Screen
Quadruple Screen
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Nuchal Translucency
Nuchal Translucency
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Study Notes
Edward Syndrome Overview
- Edward syndrome, or Trisomy 18, is a genetic disorder where there are three copies of chromosome 18 instead of two
- Occurs in approximately 1 in 3,000 to 1 in 6,000 live births
- Females are more commonly affected than males
- Only about 13% of those with Edward syndrome survive past the first year
- Survivors typically experience severe psychomotor impairment and intellectual disability
Genetic Basis of Edward Syndrome
- Increased maternal age (over 35) is a significant risk factor
- Nondisjunction during meiosis I or II leads to an extra chromosome copy
- Mosaicism, a mix of normal and trisomy cells, can occur
- Robertsonian translocation, a chromosomal fusion, is another possible cause
Clinical Features of Edward Syndrome
- Overlapping features with Patau syndrome, especially microcephaly (small head)
- Dolichocephaly, an elongated head shape, and a prominent occiput
- Craniofacial deformities and cardiac defects are common
- Renal anomalies, particularly horseshoe kidney, can occur
- Delayed development are also typical
- Polyhydramnios, excessive amniotic fluid, may develop
- Pulmonary hypoplasia, or underdeveloped lungs, can occur
- Neural tube defects such as seals, fauci meningo or myelocele
- Overlapping fingers and clenched fists are classic signs
- Rocker bottom feet, similar to Patau syndrome, are often present
True-Life Cases and Visual Indicators
- Overlapping fingers and rocker bottom feet are key visual indicators
- Stillbirth is common in Edward syndrome cases
- Elongated head with prominent occiput
- Other features include micronathia (recessed lower jaw)
- Plastic ears (unusually shaped or underdeveloped ears) also occur
Quadruple Screen in Second Trimester
- The quadruple screen measures HCG, AFP, estriol, and inhibin A levels in the mother's blood
- Decreased levels of HCG, AFP, and estriol are indicative of Edward syndrome
- Inhibin A levels can be normal or decreased
Comparison between Edwards and Patau Syndrome
- Nuchal translucency is typically high in both syndromes
- In the first trimester, both PAPP-A and HCG levels are decreased in both syndromes
- Second trimester screenings may be normal in Patau syndrome, requiring reliance on other diagnostic indicators
- Comprehensive evaluation is key, considering all diagnostic indicators and clinical features
- In Edward syndrome, estriol, AFP, and HCG levels are decreased, and inhibin levels may be low or normal
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