Introduction to Post Streptococcal Glomerulonephritis
Post Streptococcal Glomerulonephritis (PSGN) is a renal pathology that occurs following an infection with certain strains of
Streptococcus bacteria. This condition predominantly affects children and is characterized by inflammation of the
glomeruli within the kidneys. The disease follows a streptococcal throat or skin infection and manifests as a nephritic syndrome.
Histologically, PSGN is marked by the presence of diffuse glomerular hypercellularity. This hypercellularity is largely due to the proliferation of endothelial and mesangial cells and an influx of inflammatory cells, primarily
neutrophils. Under light microscopy, the glomeruli appear enlarged and crowded with cells, disrupting the normal architecture.
Electron microscopy reveals the presence of subepithelial
humps, which are deposits of immune complexes made up of antibodies, antigens, and complement components. These humps are a key diagnostic feature of PSGN. Immunofluorescence studies typically show granular deposits of
IgG and complement component
C3 along the glomerular basement membrane.
PSGN is a classic example of an immune-mediated disease. After a streptococcal infection, the immune system generates
antibodies against the bacterial antigens. These antibodies can form immune complexes with circulating antigens. When these complexes are trapped in the glomeruli, they incite an inflammatory response, leading to glomerular injury. The complement system is activated, contributing to the inflammatory process and further glomerular damage.
Clinically, PSGN presents with
hematuria (blood in urine), often described as "cola-colored" urine, due to the presence of red blood cells. Other symptoms include hypertension,
edema (swelling), and oliguria (reduced urine output). These symptoms reflect the underlying glomerular inflammation and the resultant disruption of normal kidney function.
The prognosis for PSGN is generally favorable, especially in children. The majority of pediatric patients experience complete recovery with supportive care, which includes managing blood pressure and fluid balance. However, some adults may develop
chronic kidney disease if the acute inflammation leads to significant scarring of the glomeruli.
Histological Differentiation from Other Glomerulonephritides
Distinguishing PSGN from other forms of glomerulonephritis is crucial for accurate diagnosis and management. Unlike
IgA nephropathy, which presents with mesangial IgA deposits, PSGN features subepithelial deposits and prominent C3 staining. Additionally, conditions like
membranoproliferative glomerulonephritis (MPGN) also exhibit complement deposition but differ in the pattern and location of deposits, as well as in clinical presentation.
Conclusion
Understanding the histological features of post streptococcal glomerulonephritis is essential for diagnosis and management. The distinct histopathological characteristics, including glomerular hypercellularity and subepithelial humps, aid in differentiating it from other glomerulopathies. With appropriate treatment, the prognosis of PSGN is good, especially in children, although vigilance is necessary to prevent potential progression to chronic kidney disease in adults.
