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.
The case, published in March in Child's Nervous System by clinicians in Abu Dhabi, is the third reported spinal BPOP and the first in a child, according to its authors.
A Growth Wrapped Around the Nerve Roots
The MRI showed a well-defined mass sitting inside the dura, the tough membrane surrounding the spinal cord and nerve roots, but outside the cord itself, a location doctors call intradural extramedullary. The lesion had a mixed appearance on the scan and enhanced around its edges.
Surgeons reached it through a laminotomy at L1, an operation that opens part of the bony arch at the back of the vertebra. What they found was firm, partially mineralized and densely stuck to several nerve roots. In most people, the spinal cord ends around the first or second lumbar vertebra and gives way to a bundle of nerve roots serving the legs, bladder and bowel, so a mass at that level sits in crowded territory.
Under the microscope, the tissue showed crowded cartilage cells, immature bone that pathologists call "blue bone," and a rim of reactive bone-forming cells. Together, those features established the diagnosis. After surgery, the boy's neurological function partially improved, according to the abstract.
The symptoms fit the location. Progressive leg weakness, an unsteady gait, and urinary urgency are recognized warning signs of pressure on the lower spinal cord or its nerve roots.
A Lesion Named for the Hands and Feet
BPOP was first described in 1983 as a growth on the hands and feet, and it has kept that profile. A 2024 systematic review in the Journal of International Medical Research pooled 323 cases from 101 published articles and found that about 58% involved the hands and about 21% involved the feet. Patients ranged from 3 months to 87 years old, with most cases in the second and third decades of life.
The spine barely registers in that record. The first spinal case, published in 2019 in the Asian Journal of Neurosurgery, was an intradural lesion at the T4 to T5 level of the upper back that imaging had initially suggested was a meningioma, a usually benign tumor of the membranes covering the brain and spinal cord. The 2024 review team reported a second, in a woman in her 20s whose lesion involved the bone at the T7 to T8 level.
The exact tally depends on which reports are counted. A 2023 report in Apollo Medicine described another intradural spinal BPOP in a 20-year-old woman with leg weakness. Either way, spinal cases remain a handful.
The cause of BPOP is unknown. Some patients report prior trauma, and researchers have found recurring chromosomal abnormalities and gene fusions in some lesions, but no explanation has been established.
Benign on Paper, Stubborn in Practice
Although BPOP is not cancer, it is locally aggressive and has a reputation for coming back. In the 2024 review, about 37% of patients with recurrence data had a recurrence, and some earlier series reported rates as high as 55%. The authors of the new case stress that the lesion's tendency to recur calls for long-term surveillance.
Recognizing the lesion quickly matters for another reason. On imaging, BPOP can look alarming, and the authors caution that early recognition is critical to avoid overtreatment, since a benign growth mistaken for something malignant could lead to unnecessarily aggressive therapy.
For radiologists and neurosurgeons, the practical takeaway is to keep BPOP on the list of possibilities when they encounter a mineralized mass inside the spinal dura, even though the diagnosis is extraordinarily rare.
What Remains Unknown After So Few Cases
With only a handful of spinal cases on record, doctors have little to go on when predicting how this boy will do over time. It is unclear whether spinal BPOP behaves like hand and foot lesions, whether it recurs at similar rates, or why it formed in the spinal canal at all.
The report also shows the limits of case reports. They cannot establish how often a condition occurs or which treatment works best, but they give clinicians a reference point when an unusual finding appears on a scan.
For parents, the broader lesson is not about BPOP, which remains exceptionally rare. Progressive leg weakness, trouble walking, new bladder problems, or unexplained weight loss in a child are reasons to see a clinician promptly. Most such symptoms will have other explanations, but they deserve a careful evaluation.
Key Questions Answered
What did doctors find in the boy's spine?
A firm, partially mineralized growth inside the spinal canal at L1, stuck to several nerve roots. Pathology identified it as bizarre parosteal osteochondromatous proliferation, or Nora's lesion.
Is Nora's lesion cancer?
No. It is a benign growth of bone and cartilage, but it can be locally aggressive and often recurs, so patients need long-term follow-up.
Why is this case so unusual?
BPOP almost always affects the hands and feet. The authors describe this as the third reported spinal case and the first in a child.
What symptoms did the boy have?
Progressive leg weakness, an unsteady gait, urinary urgency, and significant weight loss.
How was it treated?
Surgeons removed the lesion through a laminotomy at L1, and his neurological function partially improved afterward.
