Only forty similar cases have ever been recorded, and it is a deformity that is still “not fully understood”. The baby was born in Brazil at the Albert Sabin Children’s Hospital last January at 35 weeks.
The case report describing the tail, which was published in the Journal of Pediatric Surgery Case Reports, described his mother as previously healthy who did not drink alcohol or use illegal drugs.
However, it did note that she smoked 10 cigarettes per day during her pregnancy.
When he was born, doctors used an ultrasound to check that the tail – which had a four-centimetre ball at the end of it – did not impact the baby’s nervous system.
They then removed it in a short operation, after which doctor’s found that it was made of boneless tissue, while the ball at the end was made of fatty embryonic connective tissue.
The case report itself pointed out the risk of manipulation and removal of the extremity.
It said: “It is essential that the paediatrician or paediatric surgeon investigate the presence of occult spinal dysraphism (OSD) in patients with suspected skin lesions, as they may be the only visible abnormality and early diagnosis may prevent the evolution to serious neurological alterations.”
However, it was removed successfully without issue.
Most humans start to grow a tail while in the womb around the fourth week of gestation, but it usually disappears by the eighth week and eventually turns into the tailbone.
“These lumbosacral skin appendages are often associated with hidden spinal dysraphism and other malformations such as lipoma and anchored cord syndrome.
It also classified tails into “real tails” or “pseudo-tails”.
The report continued: “In this article, we report the case of a newborn male with the presence of a cutaneous appendix of approximately 12 cm in the left paravertebral lumbosacral region.
“Due to their common ectodermal origin, lumbosacral cutaneous appendages and other skin lesions are an important indication of nervous system involvement, and a comprehensive investigation with imaging exams is essential for a therapeutic approach and adequate follow-up, reducing the risk of progressive neurological sequelae.
“After an investigation that did not show any associated nerve alteration, the lesion was resected uneventfully.”
Additional reporting by Maria Ortega.