Polymelia: A Rare Birth Defect

What Is Polymelia?

extra limbs

Polymelia is an incredibly rare birth defect in which an infant is born with extra arms or legs. For instance, patients may have three arms or five legs. These extra limbs are often smaller than average and are usually distorted or deformed. The condition is not frequently found in humans, but is a common occurrence among animals.


The exact cause of polymelia is unknown, but it can be the result of improper cell division or proliferation.. Some cases are caused when an embryo starts as conjoined twins, but one twin degenerates and leaves a limb attached to the remaining twin.


There is only one type of polymelia.


  • Being born with an extra arm(s)
  • Being born with an extra leg(s)



Polymelia is apparent on a physical examination. Your child’s doctor will likely order diagnostic imaging, such as an x-ray or MRI, to get a more detailed view of the extra limb or limbs.


In some cases, the extra limb may be able to be surgically removed from the body. If removal of the limb could affect nearby vital organs, it is often recommended that the limbs be kept in tact and the patient learn to cope with having an extra limb.

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