Staphylococcus Infection-Associated GN - Spectrum of IgA Staining and Prevalence of ANCA in a Single-Center Cohort.
Staphylococcus infection-associated GN (SAGN) is a well recognized disease entity, particularly because of the frequent IgA-dominant glomerular immunoglobulin staining on kidney biopsy. Biopsy features can resemble two other disease entities - primary IgA nephropathy and Henoch-Schönlein purpura nephritis - posing a diagnostic pitfall. This is clinically relevant because of the crucial difference in the therapeutic approach. The diagnosis of SAGN is further complicated by the variability in the degree of glomerular IgA (and C3) staining, the extent of electron dense immune-type deposits, and positive ANCA serology in some patients.



We performed a thorough histopathologic review of our single-center cohort of 78 culture-proven SAGN biopsies to assess the spectrum of IgA staining, prevalence of ANCA serology, prevalence of subepithelial "humps," and other histologic features to distinguish from primary IgA nephropathy.



Among the 78 SAGN biopsies, IgA staining was trace in 25%, mild in 19%, moderate in 44%, and strong in 12% of the cases. C3 was frequently moderate-to-strong but was trace in 14% of the biopsies. Concomitantly trace IgA, IgG, and C3 (pauci-immune pattern) was seen in 13%. Crescents were present in 35% of the SAGN biopsies. Out of 41 patients tested for ANCA, nine (22%) were positive, including patients with endocarditis and other infections. Subepithelial humps were identified in only 31% of the SAGN biopsies.



SAGN biopsies show marked variability in IgA immunofluorescence staining and low frequency of subepithelial humps compared with poststreptococcal GN. Occasional ANCA positivity is present in cases of SAGN, even in infections other than endocarditis. Therefore, biopsy diagnosis can be difficult particularly when clinical symptoms of infection are subtle. Both the pathologist and the nephrologist should be aware of these diagnostic pitfalls.
Department of Pathology, and.
Anjali A
AA
Satoskar
Department of Pathology, and.
Sarah
S
Suleiman
Department of Internal Medicine, Division of Nephrology, Ohio State University Wexner Medical Center, Columbus, Ohio.
Isabelle
I
Ayoub
Department of Pathology, and.
Jessica
J
Hemminger
Department of Internal Medicine, Division of Nephrology, Ohio State University Wexner Medical Center, Columbus, Ohio.
Samir
S
Parikh
Department of Pathology, and.
Sergey V
SV
Brodsky
Department of Pathology, and.
Cherri
C
Bott
Department of Pathology, and.
Edward
E
Calomeni
Department of Pathology, and.
Gyongyi M
GM
Nadasdy
Department of Internal Medicine, Division of Nephrology, Ohio State University Wexner Medical Center, Columbus, Ohio.
Brad
B
Rovin
Department of Internal Medicine, Division of Nephrology, Ohio State University Wexner Medical Center, Columbus, Ohio.
Lee
L
Hebert
Department of Pathology, and.
Tibor
T
Nadasdy
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019268:Antibodies, Antineutrophil Cytoplasmic / Q000097:blood; D001706:Biopsy; D003176:Complement C3 / Q000378:metabolism; D003937:Diagnosis, Differential; D005260:Female; D005455:Fluorescent Antibody Technique; D005921:Glomerulonephritis / Q000175:diagnosis* / Q000378:metabolism* / Q000382:microbiology; D005922:Glomerulonephritis, IGA / Q000175:diagnosis*; D006801:Humans; D007070:Immunoglobulin A / Q000378:metabolism*; D007074:Immunoglobulin G / Q000378:metabolism; D007668:Kidney / Q000378:metabolism* / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D013203:Staphylococcal Infections / Q000150:complications; D055815:Young Adult
D019268:Antibodies, Antineutrophil Cytoplasmic; D003176:Complement C3; D007070:Immunoglobulin A; D007074:Immunoglobulin G
Staphylococcus; antibodies, antineutrophil cytoplasmic; biopsy; electrons; endocarditis; fluorescent antibody technique; glomerulonephritis; glomerulonephritis, IGA; humans; immunoglobulin A; immunoglobulin G; kidney glomerulus; nephritis; prevalence; purpura, Schoenlein-Henoch; staining and labeling