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Questions and Answers
What is the incidence of trisomy 18 in live births?
Which of the following congenital heart defects is commonly associated with trisomy 18?
What is the main reason for the low survival rate of individuals with trisomy 18?
What is the name of the syndrome caused by trisomy 18?
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What is the significance of the quadruple test in the diagnosis of trisomy 18?
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What is the abbreviation of the acronym PRINCE Edward, which helps in remembering the clinical features of trisomy 18?
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What is the survival rate of individuals with trisomy 18 beyond 12 months of age?
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Study Notes
Trisomy 18 (Edwards Syndrome)
- Karyotype: ♀: 47,XX,+18, ♂: 47,XY,+18
- Incidence: approximately 1 in 3,300 live births
Pathogenesis
- Caused by meiotic nondisjunction
Clinical Features
- Characteristic facial anomalies:
- Low-set ears (malformed auricle)
- Micrognathia (congenital mandibular hypoplasia)
- Prominent occiput
- Microcephaly
- Broad nose
- Cleft lip and palate, high palate
- Limb anomalies:
- Clenched fists with flexion contractures and overlapping fingers
- Rocker-bottom feet:
- Convex deformity of the plantar side of the foot
- Vertical talus
- Prominent calcaneus
- Congenital heart defects:
- Ventricular septal defect (VSD)
- Atrial septal defect (ASD)
- Tetralogy of Fallot
- Malformations of internal organs:
- Diaphragmatic hernia
- Ureter and kidney malformations (horseshoe kidneys)
- Myelomeningocele
- Omphalocele
- Severe intellectual disability
Diagnosis
- Quadruple test in the second trimester:
- Decreased free estriol
- Decreased AFP
- Decreased β-HCG
- Normal or decreased inhibin A
Prognosis
- Approximately 13% of patients survive past 12 months of age
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Description
Learn about the characteristics and features of Trisomy 18, also known as Edwards syndrome, including its incidence, pathogenesis, and clinical features. Test your knowledge of this genetic disorder!
