New Aspects of Fibrillary and Immunotactoid Glomerulonephritis

Renal diseases involving glomerular deposits of fibrillary material are an important diagnostic challenge for an ultrastructural pathologist. Several renal diseases are characterised by the presence of fibrillary material in the glomeruli. Two disorders of this type, termed ‘fibrillary glomerulonephritis’ (characterised by fibrils measuring approximately 20 nm in diameter) and ‘immunotactoid glomerulonephritis’ (characterised by larger, microtubular deposits), have been described. The possible relatedness of these two disorders and their potential association with other systemic illnesses are the subjects of current debate. Other multisystemic diseases, including amyloidosis and various forms of cryoglobulinaemia, can also present with fibrillary or microtubular deposits in the kidney. The distinction between fibrillary glomerulonephritis, immunotactoid glomerulonephritis, and other processes that have similar ultrastructural features are discussed in this review. Recently, both in fibrillary glomerulonephritis and in immunotactoid glomerulonephritis, the presence of a DnaJ homolog subfamily member 9 has been detected. This antigen is not present in amyloidosis and could be involved in the pathogenesis of these diseases. This review will discuss the role and the relevance of this antigen.