Variable Effects of Laterality Genes on Disharmony Between Different Thoraco-Abdominal Organs and Between Individual Cardiac Segments.

A significant percentage of patients with heterotaxy show disharmony between abdominal, bronchopulmonary and atrial situs. This finding is interesting in light of the variable effects of ciliary and laterality genes on different organs and different cardiac segments. Defects in ciliary and laterality genes that usually result in situs inversus or heterotaxy, may occasionally act separately at ventricular and/or great arteries segment, even in patients with normal viscero-atrial situs solitus. Some patients with situs solitus and transposition of great arteries or congenitally corrected transposition of great arteries have been shown to represent the result of partial segmental effects of laterality genes alterations. Specific effects of defects in laterality genes can explain disharmony between thoraco-abdominal organs and heart segments.