BMJ Case Reports 2017; doi:10.1136/bcr-2017-223097
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Prenatal diagnosis of left isomerism with normal heart

  1. Francisco Valente3
  1. 1Department of Gynecology–Obstetrics, Centro Hospitalar Universitário do Algarve—Unidade de Portimão, Portugal
  2. 2Department of Pediatric Cardiology, Centro Hospitalar de Vila Nova de Gaia/Espinho, EPE, Portugal
  3. 3Department of Gynecology–Obstetrics, Centro Hospitalar de Vila Nova de Gaia/Espinho, EPE, Portugal
  1. Correspondence to Dr Sara Costa, saraibcosta{at}
  • Accepted 27 October 2017
  • Published 12 November 2017


Left isomerism (LI) is characterised by loss of normal asymmetry of the thoracoabdominal organs. Consequently, viscera that normally develop on the left side are found on both sides of the body, whereas right-sided viscera may be absent. This abnormal symmetrical development of organs occurs because in the early embryonic life, there was a disruption of left–right axis orientation.

The most common reported anomalies are bilateral morphological left atria and lungs, cardiac defects, arrhythmias (because the sinus node, located in the right atrium, is absent or incompletely developed), interruption of the inferior vena cava (IVC), multiple spleens and gastrointestinal malformations such as right-sided stomach, midline liver, biliary tract abnormalities and intestinal malrotation.

This rare condition occurs in approximately 1 per 10 000–40 000 live births.1 The outcome of the fetuses with LI varies depending on the association with cardiac defects, dysrhythmias and other significant malformations.

The prenatal diagnosis is usually made …

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