Glomérulopathies à dépôts organisés d'immunoglobulines

Glomerulonephritis with organized immunoglobulin deposits are heterogeneous and may be encountered in a variety of renal disorders. It is particularly important to determine the exact types of immunoglobulin deposited and their monotypy/monoclonality, using specific anti-light chain conjugates and in some instances, anti-heavy chain subclass conjugates. The histologic pattern and identification of monotypic Ig deposits in renal tissue are in some cases sufficient for the diagnosis of AL amyloidosis, type I cryoglobulinic glomerulonephritis or “Randall-type” monoclonal immunoglobulin deposition disease (MIDD). Electron microscopy is particularly valuable for the precise localization of Ig deposits and for determing the pattern of deposition: organized, homogeneous (non-organized or granular) or mixed. New entities in the broad spectrum of Ig deposition diseases are emerging from electron microscopy studies of renal diseases. We propose here a comprehensive classification for diseases featuring the organized deposition in tissues of Ig.