A rare case of tophaceous gout manifesting as an osteolytic lesion of the acromioclavicular joint

An osteolytic lesion on imaging can be considered malignancy until proven otherwise. However, advanced stages of gout have presented with sclerotic rims and lytic lesions thought to be due to overexpression of osteoclasts. Patients have been found to demonstrate osteolytic lesions in patellar regions, which are common locations for gout to manifest; however, to our knowledge, no other cases of osteolytic gout in the acromioclavicular joint have been reported at this time. We report a rare case of a 56-year-old male who presented with acute-on-chronic left upper extremity pain and was found to have an osteolytic lesion of the shoulder on imaging. This lesion was later biopsied and found to be histologically consistent with gout. This case report aims to elucidate further understanding of the various ways that gout can present, to diagnose and treat these patients more effectively.