Final Diagnosis -- Post-infectious glomerulonephritis with IgA predominance

FINAL DIAGNOSIS

1. Diffuse endocapillary proliferative and exudative glomerulonephritis with granular mesangial and focal glomerular basement membrane iga predominant staining and numerous glomerular mesangial, focal subepithelium hump-like, and few subendothelial immune complex deposits.
2. Rare small fibrinous/cellular crescents involving approximately 3/45 (7%) glomeruli.
3. Extensive and widespread podocyte foot process effacement.

The clinical pathologic findings suggest a post-infectious glomerulonephritis with IgA predominance. The differential diagnosis includes IgA nephropathy, but IgA nephropathy, typically, does not show large subepithelial (hump like) electron dense immune deposits.

This correlates temporally with the history of a recent sore throat, although the ASO serology is negative. However, post-infectious glomerulonephritis with IgA-containing immune complex deposits in association with non-Streptococcal infections, especially staphylococcal infections, has been reported (1-3). This should be differentiated from primary IgA nephropathy (1).

Haas et al (3), studied renal biopsy findings in 13 cases of IgA-dominant post-infectious glomerulonephritis characterized by subepithelial humps on electron microscopy. They concluded that IgA-dominant post-infectious glomerulonephritis resembles post-streptococcal glomerulonephritis in its histologic spectrum and ultrastructural findings. This disorder is often associated with staphylococcal infections, often occurs in diabetics (but may occur in non-diabetics), and may spontaneously resolve if the infection is successfully treated.

IgA immune complex-associated glomerular disorders have been reported in association with HIV disease especially in Caucasians. Classic HIV nephropathy (HIVAN) is, however, not identified in the present case. A secondary form of IgA nephropathy occurs in patients with chronic liver disease associated with cirrhosis, pathologically indistinguishable from primary IgA; the absence of cirrhosis in this patient and the subepithelial hump-like immune deposits are features against this diagnosis. Podocyte foot process effacement is recognized to occur in a subset of patients with IgA glomerular disorders and HIV disease, in addition to minimal change disease. These patients, similar to those with minimal change disease, typically have significant proteinuria.

REFERENCES

1. Satoskar AA, Nadasdy G, Plaza JA, Sedmak D, Shidham G, Hebert L, et al. Staphylococcus infection-associated glomerulonephritis mimicking IgA nephropathy. Clin J Am Soc Nephrol. 2006 Nov;1(6):1179-86.
2. Nasr SH, Markowitz GS, Whelan JD, Albanese JJ, Rosen RM, Fein DA, et al. IgA-dominant acute poststaphylococcal glomerulonephritis complicating diabetic nephropathy. Hum Pathol. 2003 Dec;34(12):1235-41.
3. Haas M, Racusen LC, Bagnasco SM. IgA-dominant postinfectious glomerulonephritis: a report of 13 cases with common ultrastructural features. Hum Pathol. 2008 Sep;39(9):1309-16.

Contributed by Jennifer Picarsic, MD anf Miguel Reyes-Mugica, MD