Mesangiocapillary glomerulonephritis in a patient with Nocardia pneumonia

Membranoproliferative glomerulonephritis: pathogenetic heterogeneity and proposal for a new classification

Membranoproliferative glomerulonephritis (MPGN) is a pattern of injury that results from subendothelial and mesangial deposition of Igs caused by persistent antigenemia and/or circulating immune complexes. The common causes of Ig-mediated MPGN include chronic infections, autoimmune diseases, and monoclonal gammopathy/dysproteinemias. On the other hand, MPGN also can result from subendothelial and mesangial deposition of complement owing to dysregulation of the alternative pathway (AP) of complement. Complement-mediated MPGN includes dense deposit disease and proliferative glomerulonephritis with C3 deposits. Dysregulation of the AP of complement can result from genetic mutations or development of autoantibodies to complement regulating proteins with ensuing dense deposit disease or glomerulonephritis with C3 deposits. We propose a new histologic classification of MPGN and classify MPGN into 2 major groups: Ig-mediated and complement-mediated. MPGN that is Ig-mediated should lead to work-up for infections, autoimmune diseases, and monoclonal gammopathy. On the other hand, complement-mediated MPGN should lead to work-up of the AP of complement. Initial AP screening tests should include serum membrane attack complex levels, an AP functional assay, and a hemolytic assay, followed by tests for mutations and autoantibodies to complement-regulating proteins.

Nocardial cerebral abscess associated with mycetoma, pneumonia, and membranoproliferative glomerulonephritis

Nocardial brain abscesses remain a clinical challenge. We successfully treated a patient with nocardial brain abscess, mycetoma, pneumonia, and glomerulonephritis. Nocardial soft tissue involvement, mycetoma, is well known. However, the fact that actinomycetoma can metastasize may not be as well appreciated. The association between nocardiosis and glomerulonephritis should be better clarified.

Pulmonary Nocardiosis

Pulmonary nocardiosis is an uncommon but serious infection that is increasingly found in immunosuppressed persons, especially transplant recipients and persons with AIDS. The Nocardia species are denizens of soil and decaying plants that gain entry to humans through inhalation or inoculation. Pulmonary nocardiosis typically presents as an acute to subacute necrotizing pneumonia, with a variable clinical picture. Metastatic infections of the brain and subcutaneous tissues are common complications. Most clinical laboratories can isolate these microorganisms, but final speciation may be a challenge and antimicrobial susceptibility testing is especially difficult because of the slow rate of growth of Nocardia species. Full identification of species and susceptibility testing is important because of the epidemiologic implications and the difficulties of successfully treating these infections in immunosuppressed patients. Sulfonamides, including trimethoprim-sulfamethoxazole, remain the most reliable antimicrobials. Many alternative agents are active against Nocardia in vitro, but clinical data are limited.