‘Penile ossification remains a relatively rare condition being mentioned in very few journals, with less than 40 published case reports,’ they wrote.

They said ossification in the penis is normally a consequence of Peyronie’s disease, in which internal scarring causes the sex organ to bend sharply in one direction.

And tissue may turn to bone when calcium salts build up in a specific area over time as a result of conditions such as cancer, thyroid problems or kidney disease.

Richard Viney, a urological surgeon in Birmingham, was not involved with the case study but explained it was likely caused by extreme Peyronie’s disease.

He said the man’s condition was caused by bone forming in part of the penis called the Bucks fascia, which is essentially its tough inner lining along the shaft.   

‘In very rare cases, the scarring process [of Peyronie’s disease] is so excessive it can involve the deposition of calcium, toughening the scar tissue and this is what is being described in this case,’ he told MailOnline.

‘It is easy to think that the patient’s entire penis is calcifying but it is only the fibrous Bucks fascia just below the skin. 

‘These plaques would be palpable and hard to the touch. They can be quite extensive and it is possible with time that all of Bucks fascia could be involved, but this is unlikely. 

‘As the stretchiness of the fascia is lost, erections would be limited in their scope and there may be considerable bend. Indeed there may well be complete erectile failure.’

Mr Viney said Peyronie’s disease usually gets as bad as it will ever get after six months and that the only treatment option is surgery.

But the New York patient’s condition appears to be too advanced for even that to work, Mr Viney said, suggesting he would face a lifetime of erectile dysfunction. 

He added: ‘The whole penis won’t turn to bone as it only involves Bucks fascia so, at worst, it would only be a boney cylinder filled with the two spongy corpora [cylinders inside the shaft] and the urethra itself.’

The New York team added: ‘We couldn’t assess the [causes] since our patient decided to leave against medical advice.’

They suggested treatment could involve using painkillers, ‘stretching’ or vacuum devices, shockwave therapy or surgery.