Immunotactoid Glomerulopathy with Nontuberculous Mycobacterial Infection: A Novel Association

Immunotactoid Glomerulopathy

Immunotactoid glomerulopathy (ITG) is a rare glomerular disease that typically presents with proteinuria, hematuria, and kidney dysfunction. A kidney biopsy is essential to establish the diagnosis of ITG. ITG is characterized by glomerular electron-dense immunoglobulin deposits with hollow-cored microtubules. ITG is classified as either monoclonal or polyclonal based on immunofluorescence staining of the immunoglobulin deposits. Monoclonal ITG is associated with an underlying hematologic disorder in two-thirds of the cases, lymphoma and plasma cell dyscrasias being the most common. Polyclonal ITG is associated with autoimmune diseases but can be seen with hematologic disorders and chronic infections. Due to the preponderance of hematologic disorders in both monoclonal and polyclonal ITG, a thorough hematologic workup must be performed in all cases of ITG. In monoclonal ITG with a detectable clone, clone-directed therapy is administered to achieve hematologic remission, as the renal response is highly dependent on the hematologic response. In clone-negative monoclonal ITG, anti-B cell therapy is often used as a first-line therapy. Management of polyclonal ITG without an underlying hematologic disorder is poorly defined. Compared to monoclonal ITG, patients with polyclonal ITG have a higher risk of progression to end-stage kidney disease. Recurrence of ITG following kidney transplantation is common and is often associated with hematologic relapse.