Chapter 31: Bacterial Infection-Associated Glomerulonephritis
A 68-year-old male was admitted for management of pneumonia and septicemia. While in the hospital he developed acute kidney injury, hematuria, and subnephrotic proteinuria. He had depressed serum C3 and normal C4. ANA, ANCA, and hepatitis serologies were negative. Kidney biopsy performed showed endocapillary proliferative and exudative glomerulonephritis on light microscopy. Based on the immunofluorescence findings shown, blood cultures will likely grow one of the following pathogens:
D. Streptococcus pneumoniae
The answer is B. The immunofluorescence figure shows bright coarsely granular glomerular capillary wall and mesangial staining for C3 and IgA (“starry-sky” pattern), supporting a diagnosis of IgA-dominant bacterial infection associated glomerulonephritis. The vast majority of cases of IgA-dominant bacterial infection associated glomerulonephritis are due staphylococcal infection (most commonly associated with Staphylococcus aureus).
Which one of the following features favors IgA-dominant staphylococcus-associated glomerulonephritis over primary IgA nephropathy?
A. Normal serum complement
B. Concurrent respiratory tract infection
C. Bright glomerular staining for C3 and IgA on immunofluorescence
D. Subepithelial hump-shaped electron dense deposits on electron microscopy
E. Mesangial proliferative glomerulonephritis on light microscopy
The answer is D. Subepithelial humps are far more common in bacterial infection–associated glomerulonephritis than IgA nephropathy. Other clinical and pathologic features that favor IgA-dominant staphylococcus-associated glomerulonephritis over IgA nephropathy are initial presentation at an older age, presence of hypocomplementemia, and presence of exudative glomerulonephritis on light microscopy.
The depicted pattern of glomerular injury is more likely to be associated with one of the following types of bacterial infection:
A. Upper respiratory tract infection
C. Urinary tract infection
E. Infectious endocarditis
The answer is E. The figure shows a trichrome stain of renal biopsy section. The two glomeruli shown exhibit large cellular crescents which compress the underlying tufts. While crescents can be seen in any form of bacterial infection–associated glomerulonephritis, they are usually more common and affect a higher percentage of glomeruli in infectious endocarditis-associated glomerulonephritis.
One of the following statements is true with regards to ...