Clinicopathological characteristics and outcome of patients with fibrillary glomerulonephritis: DNAJB9 is a valuable histologic marker

Background Fibrillary glomerulonephritis (FGN) is a rare glomerular disease. DNAJB9 as a new reliable diagnostic marker for the diagnosis of FGN was discovered recently. To investigate the clinicopathological features and prognosis of DNAJB9-positive FGN, we report on a case series in a single center in China. Methods DNAJB9 immunohistochemistry was performed on renal biopsy samples from patients with FGN (n = 7), and non-FGN glomerular diseases (n = 27) were used as controls. The patients with DNAJB9-positive FGN were retrospectively analyzed. Results Strong DNAJB9 staining of glomerular extracellular deposits was observed in 6 cases of originally diagnosed FGN. One man and 5 women with a median age of 26 years were studied. The patients presented with renal insufficiency in 1 case, proteinuria in 6 cases, nephrotic syndrome in 3 cases, and microscopic hematuria in 2 cases. The histologic pattern was mesangial proliferative glomerulonephritis in 1 case and membranoproliferative glomerulonephritis in 5 cases. The glomerular deposits stained for polytypic IgG and both kappa and lambda in 3 cases, polytypic IgG without kappa or lambda in 1, monotypic IgG1-kappa in 1 and IgG1-lambda in 1. Extraglomerular deposits were identified in all cases. Congo red positivity was observed in 3 cases. All of the patients received renin–angiotensin–aldosterone system blockade and 5 of them received glucocorticoid and/or immunosuppression. At a median time of 36.2 months after biopsy, 2 cases had partial remission, 3 cases displayed no remission, and 1 case progressed to end-stage renal disease. Conclusions Extraglomerular deposits in the FGN were common. Monotypic FGN was found in young patients with a favorable renal outcome.