DNAJB9 Is a Reliable Immunohistochemical Marker of Fibrillary Glomerulonephritis: Evaluation of Diagnostic Efficacy in a Large Series of Kidney Biopsies
Alessandro Gambella,
Chiara Pitino,
Antonella Barreca,
Alberto Nocifora,
Manuela Maria Giarin,
Luca Bertero,
Luigi Biancone,
Dario Roccatello,
Mauro Papotti,
Paola Cassoni
Affiliations
Alessandro Gambella
Pathology Unit, Department of Medical Sciences, University of Turin, 10126 Turin, Italy
Chiara Pitino
Pathology Unit, Department of Medical Sciences, University of Turin, 10126 Turin, Italy
Antonella Barreca
Pathology Unit, “Città della Salute e della Scienza di Torino” University Hospital, Via Santena 7, 10126 Turin, Italy
Alberto Nocifora
Pathology Unit, “Città della Salute e della Scienza di Torino” University Hospital, Via Santena 7, 10126 Turin, Italy
Manuela Maria Giarin
Pathology Unit, “Città della Salute e della Scienza di Torino” University Hospital, Via Santena 7, 10126 Turin, Italy
Luca Bertero
Pathology Unit, Department of Medical Sciences, University of Turin, 10126 Turin, Italy
Luigi Biancone
Division of Nephrology Dialysis and Transplantation, “Città della Salute e della Scienza di Torino” University Hospital, Department of Medical Sciences, University of Turin, 10126 Turin, Italy
Dario Roccatello
CMID, Coordinating Center of the Network for Rare Diseases of Piedmont and Aosta Valley, Nephrology and Dialysis Unit (ERK-Net Member), San Giovanni Bosco Hub Hospital, University of Turin, 10144 Turin, Italy
Mauro Papotti
Pathology Unit, Department of Oncology, University of Turin, 10126 Turin, Italy
Paola Cassoni
Pathology Unit, Department of Medical Sciences, University of Turin, 10126 Turin, Italy
Fibrillary glomerulonephritis (FGN) is a rare glomerular disease characterized by a challenging diagnostic workup requiring ultrastructural identification of 20 nm-thick randomly oriented fibrillar deposits. However, the recent introduction of DNAJB9 as a putative diagnostic marker of FGN could thoroughly improve this diagnostic scenario. This study aims to assess the DNAJB9 immunohistochemical expression in a large series of FGN cases and to eventually confirm its role as a diagnostic marker of FGN. We evaluated the immunohistochemical expression of DNAJB9 (Rabbit Polyclonal, ThermoFisher) in a series of 77 FGN and 128 non-FGN cases diagnosed between January 1992 and June 2022 at the Pathology Unit of the AOU Città della Salute e della Scienza Hospital. DNAJB9 was expressed in 73 of the 74 evaluable FGN cases, mostly showing a strong glomerular positivity (68 cases). Additionally, DNAJB9 resulted positive in all challenging scenarios [early-stage (6), congophilic (4), combined (4), and uncertain (4) cases of FGN)]. DNAJB9 was negative in all non-FGN cases, eventually resulting in a specificity of 100% and sensitivity of 99%. In conclusion, we confirmed the role of DNAJB9 as a diagnostic marker of FGN. Its adoption in the clinical routine will allow a faster, more feasible, and more accurate FGN diagnosis.
