The lung in polyarteritis nodosa: a pathologic study of 10 cases.

Polyarteritis nodosa (PAN) is characterized by necrotizing arteritis of medium-sized and small arteries in various organs. Pulmonary artery involvement in PAN has been considered rare. Previously, it also has been thought that patients with PAN do not have interstitial pneumonitis and fibrosis. A detailed pathologic analysis of pulmonary diseases associated with PAN was made in 10 autopsy cases of PAN. Arteritis affecting bronchial arteries was present in seven patients (70%). The data obtained suggest that arteritis in the lung in patients with PAN is more common than has been recognized previously. Diffuse alveolar damage (DAD) involving all lobes bilaterally was present in five patients; it was acute in two patients and organizing in three. In the patients with organizing DAD the degree of fibrosis in the interstitium differed among the lobes, and the fibrosis was more severe in the lower lobe than in the other lobes. Two patients presented with interstitial fibrosis with honeycomb lung of the posterior and lateral basal segments of the lower lobes of both lungs; in one of these patients interstitial fibrosis was present in an area of organizing DAD. Five patients died of respiratory failure resulting from DAD. In conclusion, it is important to consider DAD and interstitial fibrosis as complications of PAN.