E046 Lytic lesions; metastatic disease or gout?

Abstract Background/Aims Uric acid crystal deposition in the spine is uncommonly diagnosed, although the frequency of axial involvement is thought to be as high as 14-35%. Studies have shown that spinal gout is more common in men aged 35-75 years, with a history of chronic polyarticular tophaceous gout which is not optimally controlled being a key risk factor. Recent studies have shown that spinal gout is under and misdiagnosed due to its non-specific presentation of back pain or absence of symptoms. Our case report exemplifies this diagnostic challenge. Methods In this report we describe a case of a 79-year-old male with a history of polyarticular tophaceous gout, chronic kidney disease and previous renal carcinoma treated with curative radiotherapy. He presented with a 4-week history of progressive exertional dyspnoea and orthopnoea. He was commenced on intravenous diuretics which lead to an acute kidney injury, with his eGFR dropping to 14mL/min. His preadmission allopurinol and colchicine were held and clinically he developed a flare of gout affecting his right wrist and right second and third MCP joints. A CT scan of his abdomen and pelvis, carried out to investigate potential bowel obstruction, showed no evidence of obstruction but it did reveal multiple lytic lesions in the spine with potential extension into the spinal canal at T9 and L5. He did not have any back pain and his neurological examination was normal. Results A working diagnosis of spinal metastasis with potential cord compression was made and the patient was commenced on high dose steroids. He subsequently underwent an MRI whole spine which showed marrow abnormalities and destructive soft tissues changes affecting various facet joints in the thoracic and lumbar spine. The primary differential remained metastases but due to the unusual distribution of the marrow changes in which the vertebral bodies were completely spared, the initial CT images were reviewed on spectral scanning which demonstrated uric acid deposition in the affected facet joints. The diagnosis was confirmed as gout in the spine when a PET-CT scan revealed no potential primary source of malignancy. The gout flare in his hand settled with the steroids prescribed to treat the potential cord compression and he continued to deny suffering from back pain. Conclusion A literature search demonstrates that reports of spinal gout being described as lytic lesions on CT are rare. Spinal gout should be considered as a differential in a patient with facet joint lytic lesions on imaging, without involvement of the vertebral body and where no primary malignancy is found. Our case demonstrates how dual energy CT scanning can prevent the need for invasive biopsy in cases of diagnostic uncertainty in patients with a history of poorly controlled chronic tophaceous gout. Disclosure S.K. Stewart: None. D.J. Coulter: None. C. Masih: None.