A 13-year-old boy's legs were steadily getting weaker. He had trouble walking steadily, felt sudden urges to urinate, and had lost a significant amount of weight. An MRI revealed a mass inside his spinal canal at the L1 vertebra, near the lower end of the spinal cord, and its appearance initially raised concern for a tumor or a vascular abnormality.
It turned out to be neither. After surgeons removed it, pathologists identified bizarre parosteal osteochondromatous proliferation, or BPOP, a benign growth of bone and cartilage also known as Nora's lesion. The condition almost always involves the small bones of the hands and feet.
