Sirenomelia or "Mermaid Syndrome" is a very rare disorder in which the legs are fused together, giving the appearance of a mermaid. This condition is found in approximately one out of every 100,000 live births (about as rare as conjoined twins) and is usually fatal within a day or two of birth because of complications associated with abnormal kidney and bladder development and function. It results from a failure of normal vascular supply from the lower aorta in utero. more...
Only a handful cases of patients, who did not have the usual kidney and bladder complications, survived this condition, two of them being Tiffany Yorks of the United States of America and Milagros Cerron of Peru. Both were treated with heavy plastic reconstructive surgery.
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