Glomerular IgA deposition in pulmonary diseases.

Glomerular changes of 70 cases of pulmonary diseases and 25 control cases among 1100 consecutive autopsy cases were studied by light, immunofluorescence, and electron microscopy. These pulmonary diseases consisted of 11 cases of chronic obstructive bronchiolitis (COB), 15 cases of bronchopneumonia, 4 cases of acute interstitial pneumonia, 22 cases of idiopathic interstitial pneumonia (IIP), and 18 cases of lung cancer free from IIP. Bacteriological examination of the lung was performed in these cases including control cases on autopsy. Mesangial IgA deposition was predominant in 25 out of the 70 study cases (36%) frequently accompanied by C3, whereas slight mesangial IgA deposition was observed in one of the control cases. Incidence of IgA deposition was 64% in IIP, 54.5% in COB, 13.3% in bronchopneumonia, 16.7% in lung cancer and 25% in acute interstitial pneumonia. The results of the present study suggest that recurrence or persistence of inflammatory processes of the lung leads to IgA-mediated immune abnormalities and to mild mesangial changes with predominant IgA deposition, which are similar to the immunopathologic features of IgA nephropathy.