Woman's 5-year struggle with balance and walking was caused by a 'one-in-a-million' disorder

The patient: A 50-year-old woman in New York

The symptoms: The woman went to the hospital because she could not bend her legs, walk or sit up. She also had chronic lower-back pain, recurring episodes of fever and chills, and unexplained weight loss of more than 30 pounds (14 kilograms).

What happened next: The patient told doctors that, one month earlier, she had visited another hospital due to persistent back pain, stiffness in her knees, fever and significant weight loss. However, she noted that she'd actually begun feeling discomfort in her knees and back about five years before that.

Over time, increased rigidity in her right leg began affecting her balance and caused frequent falls. Doctors prescribed her ibuprofen and physical therapy, but the stiffness and pain continued.

During the patient's first hospital visit, blood tests had revealed that her white blood cell count was normal, suggesting that she was not fighting an infection. She was not producing antibodies that might have suggested she had rheumatoid arthritis, an autoimmune disease that causes joint stiffness. Nor did she have antibodies associated with...