The incredible case of a 37-year-old woman who can rotate her arm 180 degrees without effort has been described by a group of doctors in an article for the British Medical Journal Case Reports. The unusual "trick" became possible due to the rare Gorham-Stout disease which the woman is suffering from — often referred to as the vanishing bone disease.
The woman's condition was discovered by accident after she went to a doctor complaining of a pain in her left shoulder. Doctors noticed that her shoulder was unusually "soft" and an x-ray scan showed that her humeral head that connects the arm to the shoulder had vanished. Her humerus, a bone in the upper arm, was also "disappearing." Instead of treating her condition with surgery the woman chose shoulder strengthening exercises and managed to stop the disease from progressing.
Gorham-Stout disease is extremely rare, with only 70 such cases registered in medical literature. What triggers the ailment remains a mystery, but those who suffer from it have often shown abnormal growth of blood vessels which can crush bones.