Polysplenia syndrome

Last revised by Lotof Hassan Hamdan on 6 Sep 2024

Polysplenia syndrome, also known as left isomerism, is a type of heterotaxy syndrome where there are multiple spleens congenitally as part of left-sided isomerism.

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Polysplenia is seen predominantly in female patients. It is usually diagnosed in childhood or adulthood, later than asplenia syndrome, since associated congenital heart diseases tend to be less severe than those encountered in the latter.

It is related to the associated pathology.

Polysplenia results from failure of development of the usual left-right asymmetry of organs and consists of situs ambiguus, with features of bilateral left-sidedness.

The exact cause of polysplenia is unknown. However, it is suggested that it is caused by various factors 10:

  • embryogenic

  • genetic

  • teratogenic 

It is characterized by multiple splenules without a parent spleen. It occurs on the patient’s left side but may be bilateral. The most common associated feature is inferior vena cava interruption with azygos or hemiazygos continuation 3.

Other characteristic features include:

It carries 75% mortality by age 5 though. The presence of congenital heart diseases increases mortality rate. 1-year mortality is approximately 85% with right isomerism and more than 50% with polysplenia syndrome as the latter has less association with congenital heart diseases 11.

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