Abstract
Background and importance: “Fish vertebra” is an uncommon anomaly of vertebral body shape, consisting of central depression of the superior and inferior vertebral surfaces. It has been associated with various conditions: osteoporosis, osteomalacia, hyperparathyroidism, Paget disease, sickle cell disease, multiple myeloma and systemic lupus erythematosus.
Clinical presentation: A 29-year-old male patient, previously treated for ankylosing spondylitis (with NSAIDs and TNFα inhibitor), without any clinical improvement, was admitted to our Neurosurgical Department. He complained of difficult gait, possible only with the aid of a cane, low back pain and bilateral hip pain, but without leg pain. He denied any history of recent trauma. Neurological examination was normal. Plain thoracic and lumbar spine X-rays revealed multilevel “fish vertebrae”. Lumbar spine MRI and contrast thoraco-abdominal CT scan showed fractures of multiple structures: left L4 pedicle, right L4 lamina and pars interarticularis, right II-VII costal arches, left I-V costal arches and bilateral sacral alae. We performed extensive laboratory tests that detected low seric phosphorous and PTH levels, with increased alkaline phosphatase, indicating a possible endocrinological cause for this condition. Subsequently, we decided to transfer the patient to an Endocrinological Department. A diagnosis of hypophosphatemic osteomalacia was established and increased FGF23 levels, later determined, suggested it was tumor-induced osteomalacia. Whole-body MRI was unable to locate the tumor, but Gallium-68 DOTATATE PET/CT revealed a small (15 mm in diameter), hyperfixating mass in the head of the right femur. The patient was treated with oral calcitriol and phosphate, with alleviation of symptoms. Surgical excision of the tumor was recommended, but the patient decided to postopone the operation.
Conclusion: Modern medical imaging and biochemical testing have made the leap from merely observing vertebral biconcavities to diagnosing their cause and, consequently, the possibility to adequately treat uncommon causes of “fish vertebra”, such as neuroendocrine tumor-induced osteomalacia.
Multilevel “fish vertebrae” in a patient with tumor-induced osteomalacia