A teenager who complained of stomach pain had actually been carrying his unborn ‘parasitic’ twin inside him for 15 years, doctors discovered.

Mohd Zul Shahril Saidin, from Malaysia, underwent surgery to remove the twin this month, reports Fox News.

The 15-year-old reportedly had an unborn twin with hair, legs, hands and genitals, taken out of his stomach.

It is believed to be the first case of ‘foetus in fetu’ in the country.

A rare condition, foetus in fetu occurs where – very early in the pregnancy of twins in which the foetuses share a common placenta – one foetus wraps around and envelops the other. The enveloped twin becomes a ‘parasite’ as its survival depends on the other for survival. The parasitic twin normally lacks some organs and cannot survive on their own. As the host twin has to feed the enveloped twin from the nutrients received from one umbilical cord, they usually die before birth.

In January, an Indian teenager was also rushed to hospital with chronic stomach pains – only to discover he had a parasitic twin living inside him.