Alpha-1-antitrypsin in malakoplakia.

Macrophages in malakoplakia contain large amounts of immunoreactive alpha-1-antitrypsin (AAT). The amount of AAT remains unchanged during the morphogenetic stages of the pathological process (early, granulomatous, fibrosing phases), and does not correlate with the number or the presence of Michaelis-Gutmann (M.G.) bodies. Macrophages from other pathological processes, closely resembling malakoplakia cells but without M.G. bodies, did not contain AAT, except for a few macrophages in tuberculosis and xanthogranulomatous pyelonephritis. Whatever the source and the pathogenic role of AAT in malakoplakia, its presence in all macrophages seems to be specific for this disease. Immunohistochemical staining for AAT is therefore proposed as a useful test for an early and accurate differential diagnosis of malakoplakia.