Organizing pneumonia associated with myeloperoxidase anti-neutrophil cytoplasmic antibody.

Organizing pneumonia (OP) is a clinicopathological entity that occurs idiopathically or in association with several conditions, but there are few reports about myeloperoxidase anti-neutrophil cytoplasmic antibody (MPO-ANCA)-associated OP. We describe a patient with OP whose clinical conditions improved spontaneously. Moreover, serum MPO-ANCA titers paralleled the clinical activity of the disease, which disappeared in association with disease quiescence. Based on these findings, a subset of patients may have OP related to MPO-ANCA. ANCA testing should be considered in the work-up of patients with suspected OP.