Hx: 53 y M crack cocaine user, anamnestic hypertension/dyslipidemia/chronic pain syndrome, developed 2 wks limb rash/hematuria/creatinine increase (150 μmol/L); ED admission with abdomen/thighs/legs purpura and ear necrosisLab: urea 24.8 mmol/L; cr 449; PCR 186.8 mg/mmol; Na = 137 mmol/L; K+ = 4.9 mmol/L; ANA -; ENA -; c-ANCA -; p-ANCA +; HCV/HBV/HIV neg;Renal biopsy: active focal crescentic and necrotizing GN, glomerular capillary wall thickening; tubular epithelial injury; no active vasculitisDx: concurrent AAV secondary to LAC and associated MNTx: corticosteroids, ACE inhibitor. The gene discussed is ACE; the disease is anti-neutrophil cytoplasmic antibody-associated vasculitis.