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.

The term isomerism is derived from Greek: "iso" meaning equal and "meros" meaning part.

Article information

rID: 28739
Synonyms or Alternate Spellings:
  • Isomerisms

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Cases and figures

  • Case 1: right-sided
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  • Case 2: left isomerism with polysplenia syndrome
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