IgA-dominant infection-associated glomerulonephritis in the pediatric population

Acute Postinfectious Glomerulonephritis

Postinfectious glomerulonephritis (PIGN) is a leading cause of acute glomerulonephritis in children. The presentation of PIGN can vary from asymptomatic microscopic hematuria incidentally detected on routine urinalysis to nephritic syndrome and a rapidly progressive glomerulonephritis. Treatment involves supportive care with salt and water restriction, and the use of diuretic and/or antihypertensive medication, depending on the severity of fluid retention and the presence of hypertension. PIGN resolves completely and spontaneously in most children, and the long-term outcomes are typically good with preserved renal function and no recurrence.

Staphylococcus aureus Infection-Related Glomerulonephritis with Dominant IgA Deposition

Since 1995, when we reported the case of a patient with glomerulonephritis with IgA deposition that occurred after a methicillin-resistant Staphylococcus aureus (MRSA) infection, many reports of MRSA infection-associated glomerulonephritis have accumulated. This disease is being systematized as Staphylococcus infection-associated glomerulonephritis (SAGN) in light of the apparent cause of infection, and as immunoglobulin A-dominant deposition infection-related glomerulonephritis (IgA-IRGN) in light of its histopathology. This glomerulonephritis usually presents as rapidly progressive glomerulonephritis or acute kidney injury with various degrees of proteinuria and microscopic hematuria along with an ongoing infection. Its renal pathology has shown several types of mesangial and/or endocapillary proliferative glomerulonephritis with various degrees of crescent formation and tubulointerstitial nephritis. IgA, IgG, and C₃ staining in the mesangium and along the glomerular capillary walls have been observed on immunofluorescence examinations. A marked activation of T cells, an increase in specific variable regions of the T-cell receptor β-chain-positive cells, hypercytokinemia, and increased polyclonal immune complexes have also been observed in this glomerulonephritis. In the development of this disease, staphylococcal enterotoxin may be involved as a superantigen, but further investigations are needed to clarify the mechanisms underlying this disease. Here, we review 336 cases of IgA-IRGN and 218 cases of SAGN.