Isomerism is a term which in general means 'mirror-image' and refers to finding normally-asymmetric bilateral structures to be similar. It is used in the context of heterotaxy and is of two types:
- left isomerism
- right isomerism
Mirror image of the structures on the left side of the chest along the left-right axis of the body, i.e. patients with isomeric left atrial appendages frequently have bilobed lungs bilaterally and each with a long bronchus 1. Additionally, they have polysplenia and pulmonary veins connecting to both atrial chambers.
Mirror image of the structures on the right side of the chest along the left-right axis of the body, i.e. patients with isomeric right atrial appendages frequently have trilobed lungs bilaterally and each with a short bronchus 1. Additionally characterized by asplenia.
100% symmetry does not occur.
History and etymology
The term isomerism is derived from Greek: "iso" meaning equal and "meros" meaning part.
- 1. Kim SJ. Heterotaxy syndrome. Korean Circ J. 2011;41 (5): 227-32. doi:10.4070/kcj.2011.41.5.227 - Free text at pubmed - Pubmed citation
- 2. Applegate KE, Goske MJ, Pierce G et-al. Situs revisited: imaging of the heterotaxy syndrome. Radiographics. 19 (4): 837-52. Radiographics (full text) - Pubmed citation
- 3. Perloff JK. The cardiac malpositions. (2011) The American journal of cardiology. 108 (9): 1352-61. doi:10.1016/j.amjcard.2011.06.055 - Pubmed