Quiz page: February 2002 American Journal of Kidney Diseases   American Journal of Kidney Diseases  Volume 39, Issue 2, Pages xlviii-xlvx (February 2002) DOI: 10.1053/ajkd.2002.31818 Copyright © 2002 National Kidney Foundation, Inc Terms and Conditions

Fig. 1A What lesion is evident? (Jones' silverstain, x400) The light microscopy shows a crescentic process, with mild mesangial matrix and cell increase. The differential at this point includes both immune complex, pauciimmune, and anti-GBM etiologies of the crescentic lesion. American Journal of Kidney Diseases 2002 39, xlviii-xlvxDOI: (10.1053/ajkd.2002.31818) Copyright © 2002 National Kidney Foundation, Inc Terms and Conditions

Fig. 1B What abnormalities do you see? (transmission electron microscopy, x4,000) There are a moderate number of medium-sized mesangial deposits. There is partial foot process effacement. There are no peripheral loop deposits. American Journal of Kidney Diseases 2002 39, xlviii-xlvxDOI: (10.1053/ajkd.2002.31818) Copyright © 2002 National Kidney Foundation, Inc Terms and Conditions

Fig. 1C The amount of deposits is more than typical of pauciimmune glomerulonephritides, such as Wegener's granulomatosis or microscopic polyangiitis. However, to make a specific diagnosis, immunofluorescence studies are invaluable. In this case, there was 2+ mesangial IgA staining, with lesser 1+ staining for IgM, C3 and lambda light chain, and trace kappa light chain. There was no staining for IgG or C1q. These findings are diagnostic of IgA nephropathy. The crescents indicate a worse prognosis. (anti-IgA antibody immunofluorescence, x400). American Journal of Kidney Diseases 2002 39, xlviii-xlvxDOI: (10.1053/ajkd.2002.31818) Copyright © 2002 National Kidney Foundation, Inc Terms and Conditions