Although both are immune-mediated conditions triggered by hydralazine, hydralazine-induced lupus typically presents with positive ANA and anti-histone antibodies without ANCA positivity, whereas hydralazine-induced AAV involves ANCAs (especially MPO or PR3) and often leads to small-vessel vasculitis, making the distinction between the two a key diagnostic dilemma to be solved in both clinical diagnosis and management. The gene discussed is BTG3; the disease is systemic lupus erythematosus.