Kudose Satoru, Batal Ibrahim, Lucia John, Patel Purvi, Soni Rajesh K, Markowitz Glen S, D'Agati Vivette D, Stokes M Barry
Department of Pathology and Cell Biology, Columbia University Irving Medical Center, New York, New York.
Department of Pathology and Cell Biology, Columbia University Irving Medical Center, New York, New York.
Am J Kidney Dis. 2023 Jan;81(1):114-117. doi: 10.1053/j.ajkd.2022.05.018. Epub 2022 Aug 2.
Rare cases of immunoglobulin G (IgG)-dominant immune complex-mediated glomerulonephritis demonstrate immunoglobulin subclass restriction without light chain restriction. Some of these cases may represent proliferative glomerulonephritis with monotypic immunoglobulin deposits (PGNMID) in which monotypic immunoglobulin is obscured by coexisting polytypic immunoglobulin. However, rigorous demonstration of this possibility is lacking to date. Here, we describe a case of IgG3-restricted immune complex-mediated glomerulonephritis without light chain restriction that apparently "transformed" into IgG3κ-PGNMID in a subsequent biopsy. We demonstrate, using several ancillary techniques, including use of the newly described antibodies directed against the conformational epitope at the junctions of heavy and light chains (HLC-IF), that the first biopsy likely represents IgG3κ-PGNMID in which monotypic IgG3κ was hidden by polytypic IgM. This case underscores the need to consider PGNMID in a differential diagnosis of IgG-dominant immune complex-mediated glomerulonephritis without light chain restriction and highlights the potential utility of IgG subclass staining and HLC-IF in such cases to detect monotypic immunoglobulin that may be obscured by coexisting IgM and/or IgA deposits.
罕见的免疫球蛋白G（IgG）为主的免疫复合物介导的肾小球肾炎病例显示出免疫球蛋白亚类受限而轻链不受限。其中一些病例可能代表伴有单型免疫球蛋白沉积的增殖性肾小球肾炎（PGNMID），在这种情况下，单型免疫球蛋白被共存的多型免疫球蛋白掩盖。然而，迄今为止缺乏对此可能性的严格论证。在此，我们描述了一例IgG3受限的免疫复合物介导的肾小球肾炎病例，无轻链受限，在随后的活检中明显“转变”为IgG3κ-PGNMID。我们使用多种辅助技术，包括使用新描述的针对重链和轻链连接处构象表位的抗体（HLC-IF），证明首次活检可能代表IgG3κ-PGNMID，其中单型IgG3κ被多型IgM掩盖。该病例强调在无轻链受限的IgG为主的免疫复合物介导的肾小球肾炎鉴别诊断中需要考虑PGNMID，并突出了IgG亚类染色和HLC-IF在此类病例中检测可能被共存的IgM和/或IgA沉积掩盖的单型免疫球蛋白的潜在效用。
