Immunotactoid and fibrillary glomerulopathies are very rare renal deposition diseases that are often grouped together. Their prevalence is unknown but around 50 cases have been reported in the literature so far. The majority of patients are over 50 years of age and there is a peak in the occurrence of immunotactoid glomerulopathy towards 60 years of age. These glomerulopathies are characterised by proteinuria with a nephrotic syndrome in two thirds of cases, often associated with microscopic, or sometimes macroscopic, haematuria. Chronic renal insufficiency is present in 80% of patients and terminal renal failure occurs in 50% of patients within 1 year of disease onset. Immunotactoid glomerulopathy is associated with lymphoproliferative disorders but the aetiology of fibrillary glomerulopathy remains unknown. Diagnosis revolves around analysis of renal biopsies by light microscopy, immunofluorescence and electron microscopy. Light microscopy reveals abnormal deposits in the flocculus, within the mesangial axis, and along the endothelial or external sides of the glomeruli walls. Unlike amyloid deposits, the deposits in immunotactoid and fibrillary glomerulopathy do not react positively to Congo red. These results are confirmed by immunohistochemical studies often showing non-amyloid monotypic deposits in the case of immunotactoid glomerulopathy, and IgG4 polyclonal deposits in fibrillary glomerulopathy. In some cases, the glomeruli take on the aspect of mesangial nodules. Electron microscopy analysis allows organised and granular deposits to be distinguished. In immunotactoid glomerulopathy, the deposits are microtubular, with a diameter varying between 20 and 50 nm. Fibrillary glomerulopathy is characterised by the presence of fibrils varying in size between 15 and 20 nm (compared to between 8 and 12 nm for amyloid fibrils). The differential diagnosis should include membranoproliferative glomerulonephritis (see this term) and diabetic nodular glomerulosclerosis (Kimmelstiel-Wilson type). Treatment with corticoids and immunosuppressors is usually proposed but the effectiveness of these therapies has not been fully established. Anti-CD20 antibody therapy has been used in some cases. Renal transplantation may be proposed but there is a risk of recurrence. The prognosis is severe.
Last update: July 2008