Doctors performing an X-ray on a New York man's pelvis were astonished to find that his penis was turning to bone.
The 63-year-old, who had a history of alcoholism, had fallen in the street and after suffering knee pain had admitted himself to the emergency department of a New York hospital.
A physical examination found only penile pain and so doctors conducted the X-ray, according to an article published in the journal Urology Case Reports.
They were not surprised to find significant degenerative changes to his right hip, as the man walked with a cane, but they were shocked by what else they saw.
The journal reports they found "extensive plaque-like calcification along the expected distribution of the penis."
In layman's terms - his penis was turning to bone.
When the doctors delivered the hard news to the patient he discharged himself from the hospital and no further examinations or tests could be performed.
Known as penile ossification, the condition is extremely rare with fewer than 40 published case reports.
It is commonly linked to Peyronie's Disease, a condition which causes a curvature of the penis.
In most cases bone only forms on part of the penis, making this case even more unusual as the calcification occurred along the length of the shaft.
Treatment depends on the severity of the condition and includes painkillers and stretching or vacuum devices, though more advanced cases require surgery.
A 2013 study looked at the possibility that penile ossification was a throwback to our animal ancestors as most mammals have a penile bone, or os penis.
It is thought that humans evolved without an os penis because the human male tends to accompany a single female for long periods of time, allowing for frequent mating of a short duration.
There is also speculation that the lack of a penile bone in humans evolved as a result of sex selection, as it requires that human males must be in good physical health to sustain an erection, signalling to females that they are good genetic specimens.