A 30-year-old man presents with joint pain, skin rash, and kidney problems. He was initially suspected to have lupus, but his ANA and other autoimmune tests are negative. What could be the diagnosis?
While these symptoms initially point to lupus, the negative ANA and other autoimmune tests suggest a different diagnosis, such as Henoch-Schönlein purpura (HSP). HSP is a small-vessel vasculitis that can cause skin rash, joint pain, and kidney disease. It's more common in children but can occur in adults. Diagnosis is usually based on clinical presentation.