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Radiology
Mosaic Trisomies 8, 9, and 16
Built from Obstetric Imaging
What’s inside
6 sections · 91 slides
Overview
- What this topic covers
The idea behind mosaic trisomy
An extra chromosome in some cells, not all
- Start with the counting problem
- Most extra chromosomes end the pregnancy
- The exception is mosaicism
- Why the phenotype varies so much
- Karyotype with an extra chromosome
- How the extra chromosome gets in
- Nondisjunction during egg and sperm formation
- Two roads to a mosaic body
- Trisomy rescue explained
- Where the trisomic cells hide
- Chorionic villi and decidua on gross inspection
- Why the tissue you test matters
- The three conditions in this topic
Mosaic trisomy 8
Also called Warkany syndrome
- What mosaic trisomy 8 is
- 2–4
- Complete trisomy 8 does not survive
- Chromosome 8 and its banding map
- How mosaic trisomy 8 arises
- What affected children look like
- More features to look for
- Heart and brain involvement
- What ultrasound may show
- Reading those ultrasound signs
- The corpus callosum and the ventricles
- What MRI adds
- What else could it be
- Finding it before birth
- Chorionic villi under the microscope
- Confirming the diagnosis
- How amniocentesis is performed
- Diagnosis after birth
- The blood cancer risk
- Abnormal white cell on a blood film
- Trisomy 8 in four lines
Mosaic trisomy 9
Rare, and usually severe
- What mosaic trisomy 9 is
- 0.1%
- Who it affects
- How mosaic trisomy 9 arises
- From error to mosaic embryo
- The clinical picture
- Typical physical features
- How long children live
- What ultrasound shows
- Cross-section of the umbilical cord
- Why a two-vessel cord matters
- Brain findings on MRI
- The main differential
- Recognising trisomy 18
- Making the diagnosis before birth
- Care after birth
- Trisomy 9 in four lines
Mosaic trisomy 16
The commonest trisomy in human pregnancy
- What trisomy 16 is
- 1.5%
- Sex distribution
- How trisomy 16 arises
- Nondisjunction in maternal meiosis I
- Why the error is almost always maternal
- How a survivor becomes mosaic
- The trisomy 16 pathway
- 35.7 wk
- Physical findings at birth
- The heart defects
- A hole between the pumping chambers
- Why the lungs stay small
- What ultrasound shows
- Growth and the placenta
- What MRI adds
- What else could it be
- Making the diagnosis before birth
- Counselling the parents
- Life after the neonatal period
- Trisomy 16 in four lines
Putting it together
One pathway, three very different outlooks
- The prenatal pathway
- The three side by side
- What the referring physician needs to know
- The common ground
- Key points: trisomy 8
- Key points: trisomy 9
- Key points: trisomy 16
- Suggested readings
- Suggested readings (continued)
- References
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- Acknowledgment
- Obstetric Imaging: Fetal Diagnosis and Care, 2nd Edition