A 66-year-old who was dubbed "the man who can't catch AIDS" has taken his own life.
Stephen Crohn committed suicide in New York last month, his sister Amy told the New York Times.
"My brother saw all of his friends dying and he didn't die," she said.
"He went through a tremendous amount of survivor guilt about that and said to himself 'There's got to be a reason'. "
Crohn's unique condition was discovered when he began caring for his partner Jerry Green, who contracted AIDS in 1978, and eventually became one of the first to die of the as yet unnamed disease.
Crohn had been as sexually active as his friends and had taken no precautions, yet never became infected.
In a nutshell, Crohn's immunity comprised of a flawed receptor, CCR5, which prevented HIV from infecting his CD4 white blood cells.
But while his genetic quirk helped doctors gain a deeper knowledge of the HIV virus, Crohn, who was described as 'the man who can't catch AIDS' by The Independent in 1996, was uncomfortable with his medical notoriety.
"What's hard is living with the continuous grief," he said in a 1999 interview Surviving AIDS.
"You kept losing people every year - six people, seven people. Last week, a friend of mine's obit was in the paper. It's not easy when you're losing friends and you're that young, and it goes on for such a long period of time.
"And the only thing you could compare it to would be to be in a war."
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