MPO and chronic obstructive pulmonary disease: AAV-ANCA—associated vasculitis; ANCA—anti-neutrophil cytoplasmic antibody; COPD—chronic obstructive pulmonary disease; DM2—myotonic dystrophy type 2; EGPA—eosinophilic granulomatosis with polyangiitis; GERD—gastroesophageal reflux disease; HF—heart failure; HFrEF—heart failure with reduced ejection fraction; GPA—granulomatosis with polyangiitis; MPA—microscopic polyangiitis; MPO—myeloperoxidase; PR3–proteinase-3.