Joint Pain and Proteinuria

A 66-year-old man had bilateral carpal tunnel syndrome and 6 years of chronic joint pain and stiffness of the shoulders, hips, and knees. He reported occasional bruising around his eyes; physical examination showed raised soft tissue masses around the sternoclavicular joints and scapulae, and laboratory examination was notable for significant levels of protein and albumin. What is the diagnosis and what would you do next?
Source: JAMA - Journal of the American Medical Association - Category: General Medicine Source Type: research