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Laterality defects in conjoined twins: implications for normal asymmetry in human embryogenesis
American Journal of Medical Genetics
|November 1, 1988
Summary
Conjoined twins with fused hearts often show abnormal organ positioning (laterality defects), particularly in the right twin. This suggests heart rotation is crucial for normal embryonic development and organ arrangement.
Area of Science:
- Developmental Biology
- Embryology
- Teratology
Background:
- Conjoined twinning presents unique challenges for understanding human development.
- Investigating laterality defects in conjoined twins offers insights into early embryonic patterning.
Observation:
- Studied six conjoined twin pairs (four dicephalus, two ischiopagus).
- Three dicephalus pairs exhibited right-sided laterality abnormalities, including abnormal aortic arch, reversed great vessels, lung isomerism, asplenia, and situs inversus.
- These three pairs also shared fused hearts with similar orientations.
Findings:
- Dicephalus twins with fused hearts showed significant laterality defects in the right twin.
- Ischiopagus twins with separate hearts displayed normal visceral laterality.
- One dicephalus pair with a midline, normally rotated heart had normal situs.
Implications:
- Cardiac rotation may initiate embryonic lateralization.
- Abnormal cardiac rotation could lead to visceral laterality defects in conjoined twins.
- Findings provide a potential mechanism linking heart development to overall embryonic asymmetry.