What are fibrillary and immunotactoid glomerulonephritis?
Fibrillary and immunotactoid glomerulonephritis are very uncommon non-amyloid (Congo red negative) forms of Ig-associated kidney disease with abnormal tissue deposits from fibrils. Similar to LCDD, they usually present with a glomerulonephritis picture (hematuria and proteinuria, hypertension, and kidney impairment).
They can only be distinguished from LCDD by kidney biopsy and especially electron microscopy, where the size and characteristics of the deposits differ. Fibrillary glomerulonephritis does not usually associate with a paraprotein and has polyclonal IgG deposits, whereas immunotactoid disease may be associated with hematologic disorders (lymphoma, leukemia) and have monoclonal IgGλ or IgG κ deposits and in some cases a circulating paraprotein. The treatment of fibrillary disease is often attempted with steroids and cytotoxics, but the response is poor. Immunotactoid disease may respond to treatment of the underlying hematologic disorder. Progression to end-stage kidney disease is frequent and can occur within a few years.
