An Australian man who discovered he was intersex in his 50s has revealed the biggest symptom he experienced prior to his diagnosis.

Intersex is the term applied to bodies “that fall outside the strict male/female binary” through either an individual’s reproductive or sexual anatomy, according to Planned Parenthood.

Estimates have claimed that around 1-2 in 100 people born in the US are intersex.

The condition can result in people having genitals or internal sex organs that don’t align with traditional male/female categories. For example, someone who’s intersex may have both ovaries and testicles.

Some also are born with combinations of chromosomes that are different from XY (male) and XX (female), like XXY.

Rob Wilson, a poultry farmer from Australia, was born with both male and female genitals. As per reports, Rob was operated on at just three days old, with doctors stitching up his vagina.

He lived as a typical man until he was in his 50s, though experienced various medical problems throughout his life, including regular back pain.

Rob – who shared his story with ABC Australia: Back Roads – took testosterone every day from the age of eight and underwent dozens of surgical interventions. It transpired that Rob was still menstruating, only he had no way of releasing it.

His body subsequently reabsorbed the blood, leaving him with unusually high iron levels.

But most shocking of all? Rob only learned of his condition when his dying aunt called him on her deathbed.

“Just before she died, she rang me up and said, ‘You better come and see me, I’ve got some information you need,’” Rob explained.

She told him that he was born with a rare chromosomal condition called 48,XXXY, which affects between one in 17,000 and one in 50,000 males worldwide.

“It made a lot of sense to me because I worked on the department of main roads and I used to get the stitch every so often, I thought ‘Oh it’s just a stitch’ but it appears that was actually when I was having my monthly periods.”

Finally, Rob could put the pieces together. “My parents never ever really spoke about it,” he said. “Dad used to say, ‘Oh look, Rob’s different, but there’s nothing wrong with him,’ and that was it.

“I just got on with life. Dad used to say, ‘You can do anything anyone else can do, boy, if you set your mind to it.”

Rob now flies to Ukraine every year for ongoing treatment in keeping his hormones balanced – the country saw a rise in similar cases in the aftermath of the Chernobyl nuclear disaster.

Exactly what caused Rob’s condition is a mystery, but he has a theory that revolves around the idea that his father – who was a prisoner of war during World War II – was the subject of Nazi experiments that saw his captors inject him “with stuff”.

“Whether that was something they was experimenting with or not, I don’t really know,” Rob said.