Anti-neutrophil cytoplasmic antibodies

A positive ANCA can be seen in multiple vasculitic, autoimmune, infectious and malignant conditions.  A positive ANCA by immunofluorescence should be followed by antigen testing for myeloperodixase (MPO--typically P-ANCA pattern) or proteinase-3 (PR3--typically a C-ANCA pattern). 

C-ANCA is associated with Wegener's granulomatosis, microscopic polyarteritis, and Churg-Strauss Syndrome. 

P-ANCA is associated with microscopic polyarteritis, pauci-immune glomerulonephritis, Churg-Strauss Syndrome, drug-induced syndromes (hydralazine, PTU, penicillamine, mincocycline), ulcerative colitis, autoimmune liver disease, rheumatoid arthritis, Systemic Lupus Erythematosus, HIV and chronic infectious and neoplastic diseases.