Abstract Background/Aims Atraumatic limb pain is a common presentation to urgent and emergency services. This case illustrates a tortuous diagnostic journey with involvement of several clinical teams and uncertainty persisting until the very end. Methods An otherwise well 27-year-old man presented to minor injuries after waking with a large, tender effusion to his left knee. He reported that his knee had given way the previous day. Septic arthritis was unlikely given the absence of pyrexia, a lack of risk factors, and unremarkable inflammatory markers. His X-ray ruled out a fracture and confirmed a large effusion. A soft tissue injury was felt most likely, so the patient was issued a knee splint and crutches and discharged with orthopaedic follow-up. In clinic two weeks later, MRI was organised to assess for meniscal pathology, but instead showed an area of well-demarcated bone erosion to the lateral margin of the patella, which had been replaced by a 22 x 15 x 12mm mass of indeterminate soft tissue material. Radiological differentials included inflammatory and neoplastic causes, gout, pigmented villonodular synovitis, or a giant cell tumour of the patella. He was referred to the sarcoma MDT who added synovial chondromatosis as a further differential. Core biopsy of the lesion was arranged. Histology demonstrated variably-sized deposits of pale, acellular, crystalline material surrounded by fibrous tissue. There was a florid histiocytic and foreign body giant cell reaction to these deposits. His serum urate was 595µmol/L. A diagnosis of tophaceous gout was made on the basis of these findings, and urate-lowering therapy commenced. Results Gout is a common cause of atraumatic arthralgia but is relatively rare in those under the age of 30, with an estimated prevalence of 0.4%. Gouty tophi are considered a feature of advanced gout and typically emerge after at least 10 years of uncontrolled gout. It is unusual for tophi to be the presenting complaint for a patient with gout, and the patella is a rare location for tophi to occur. This patient posed a diagnostic challenge due to this very unusual combination of features. Urgent care, rheumatology, orthopaedics, sarcoma MDT, radiology, and histopathology teams were all involved in reaching this diagnosis. The process of ruling out a life-threatening cause and arriving at a solution proceeded efficiently thanks to effective communication between teams, appropriate referrals, and the availability of expertise. Conclusion There is scant reporting in the literature of tophi as the index presentation of gout. This case serves as a reminder that the condition should be actively considered in the differential diagnosis of atraumatic, or mildly traumatic, joint pain in young adults. This is particularly important in the context of the increased cardiovascular risk conferred by the condition. Disclosure E. Wheatley: None. S. Langdon: None. C. Chown: None. J.A.W. Mogg: None.
Wheatley et al. (Wed,) studied this question.