[Latest updates on immunotactoid glomerulopathy and fibrillary glomerulonephritis]

Various hematologic malignancies can lead to renal complications. The most common of these hemopathies to affect the kidney is multiple myeloma, however an increasing number of kidney diseases are associated with other monoclonal gammopathies. It is recognized that clones in small abundance can be responsible for severe organ damage, thus the concept of monoclonal gammopathy of renal significance (MGRS) has emerged. Although the hemopathy in these patients is more consistent with monoclonal gammopathy of undetermined significance (MGUS) than with multiple myeloma, the diagnosis of a renal complication changes the therapeutic management. Preservation and restoration of renal function is possible with treatment targeting the responsible clone. In this article, we take as an example immunotactoid and fibrillary glomerulopathies, two distinct entities with different etiologies and consequently different management. Immunotactoid glomerulopathy is most often associated with monoclonal gammopathy or chronic lymphocytic leukemia, the deposits on renal biopsy are monotypic, and treatment is therefore based on clone targeting. Fibrillary glomerulonephritis, on the other hand, is caused by autoimmune diseases or solid cancers. Deposits on renal biopsy are in the vast majority polyclonal. There is a specific immunohistochemical marker, DNAJB9, and treatment is less well established.