Staphylococcus infection-associated glomerulonephritis mimicking IgA nephropathy.

Area of Science:

• Nephrology
• Infectious Diseases
• Pathology

Background:

• The association between Staphylococcus infection and glomerulonephritis (GN) is well-established in Japan but less recognized in North America.
• Recent observations at a single institution identified eight cases of IgA-predominant or -codominant GN in patients with underlying staphylococcal infections, excluding endocarditis.

Purpose of the Study:

• To investigate the occurrence and characteristics of Staphylococcus infection-associated GN in North America.
• To highlight the importance of differentiating this condition from primary IgA nephropathy for accurate patient management.

Main Methods:

• Analysis of eight renal biopsies from patients with staphylococcal infections and GN.
• Comparison with eight control cases of primary IgA nephropathy.
• Utilized routine renal biopsy methodologies, including immunofluorescence and electron microscopy.

Main Results:

• Five patients had methicillin-resistant Staphylococcus aureus (MRSA) infections, one had methicillin-resistant S. epidermidis (MRSE), and two had methicillin-sensitive S. aureus.
• All patients presented with acute renal failure, active urine sediment, and severe proteinuria.
• Renal biopsies showed varying degrees of glomerular hypercellularity, with some exhibiting hyalin thrombi; immunofluorescence confirmed IgA predominance, and electron microscopy revealed mesangial deposits.

Conclusions:

• Staphylococcus infection-associated GN, including MRSA, is occurring in the US and may be increasing.
• Accurate differentiation from primary IgA nephropathy is critical to prevent inappropriate immunosuppressive therapy.