[A case of idiopathic pulmonary arteritis with positive anti-myeloperoxidase antibodies].

A 38-year-old woman was referred to our hospital for severe pulmonary hypertension (pulmonary arterial pressure 63/36 mmHg). Digital subtraction angiography showed complete obstruction of the right main pulmonary artery and severe stenosis of the left main pulmonary artery. Although there were no symptoms or signs of systemic arterial lesions, the initial diagnosis was aortitis syndrome with pulmonary arterial involvement, and prednisolone therapy was started (60 mg/day). Pulmonary arterial pressure decreased to 53/12 mmHg. At a dosage of 20 mg/day, however, multiple nodular shadows were present on the X-ray film of the chest, but they disappeared after the dosage was increased. The level of anti-myeloperoxidase antibodies in her serum changed at almost the same time as multiple nodular shadows appeared on the chest X-ray film. Because anti-MPO antibodies have been never detected in patients with aortitis syndrome, polyangitis overlap syndrome was suspected. However, we found no evidence of systemic vasculitis; that is, vasculitis in other organs, including the kidney and the skin. Therefore, we made a diagnosis of idiopathic pulmonary arteritis with positive anti-MPO antibodies.