Situs Ambiguous (Heterotaxy)
Epidemiology:
- Right isomerism:
- Left isomerism:
Common sites:
Gross features:
- right isomerism (asplenia syndrome):
- bilateral
right-sidedness
- bilateral right
atria
- both atrial appendages are pyramidal in shape
- single ventricle (70%)
- double-outlet
right ventricle
- bilateral SVC (50%)
- dextrocardia (heart apex to right of midline) (40%)
- central liver,
symmetrical
- absent spleen
- 3 lobes in both
lungs
- total anomalous pulmonary return (35%)
- short, eparterial bronchi bilaterally
- descending aorta
and IVC on same side of the spine
- total anomalous
pulmonary return
- left isomerism (polysplenia syndrome):
- bilateral
left-sidedness
- bilateral left atria
- multiple spleens
(often as many as 6)
- 2 lobes in both
lungs
- long hyparterial bronchi bilaterally
- interruption of IVC with azygous
or hemiazygous continuation often
- absence
of hepatic segment of IVC
- IVC drains into azygous
vein, which empties into SVC
- bilateral SVC (33%) or right SVC (33%)
- biliary atresia
- absent
gallbladder
- spectrum between
the above two
- Other features of
both left and right isomerism:
- Common atrium
- Intestinal fixation
and rotation abnormalities
- Facial defects
- CNS defects
- Hiatal hernias
- Horseshoe kidney
- Renal hypoplasia
Histologic features:
Immunophenotype:
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Marker:
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Sensitivity:
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Specificity:
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Molecular features:
Other features:
- cardiac anomalies
results in high mortality and morbidity in the first year of life
- largely heterogenous collection of both genetic and environmental
factors
- increased
incidence in consanguinity
- multifactorial, with some familial predisposition
References: