Introduction to Acute Post Streptococcal Glomerulonephritis
Acute post streptococcal glomerulonephritis (APSGN) is an
immune-mediated disease that follows an infection with specific nephritogenic strains of group A
beta-hemolytic Streptococcus. This condition primarily affects children and is characterized by the sudden onset of hematuria, proteinuria, edema, and hypertension.
Histological Features
On a histological level, APSGN is marked by diffuse glomerular hypercellularity due to an increase in
inflammatory cells such as neutrophils and monocytes. The glomeruli exhibit proliferation of both endothelial and mesangial cells. A key feature noted under light microscopy is the presence of numerous neutrophils within the glomerular capillaries, contributing to the hypercellular appearance.
Electron microscopy reveals subepithelial electron-dense deposits, commonly known as "humps," that lie on the epithelial side of the glomerular basement membrane. These deposits are composed of immune complexes, including IgG and C3 components. Immunofluorescence microscopy typically shows granular deposits of IgG and C3 along the glomerular basement membrane and within the mesangium.
Pathogenesis
The pathogenesis of APSGN involves the formation of
immune complexes that deposit in the glomeruli, triggering an inflammatory response. After a streptococcal infection, the body produces antibodies that form complexes with streptococcal antigens. These complexes circulate in the bloodstream and eventually deposit in the glomeruli, prompting complement activation and recruitment of inflammatory cells, leading to glomerular injury.
Clinical Presentation
Clinically, patients with APSGN present with a triad of symptoms:
hematuria,
edema, and
hypertension. Hematuria is often described as tea or cola-colored urine. Edema primarily affects the face and periorbital regions but can also involve the extremities. Hypertension results from fluid overload and renal dysfunction.
Diagnosis
The diagnosis of APSGN is based on clinical presentation, laboratory findings, and sometimes a renal biopsy. Laboratory tests typically show elevated antistreptolysin O (ASO) titers or other streptococcal antibodies, reduced serum C3 levels, and the presence of red blood cell casts in the urine. In cases where a biopsy is performed, histological examination confirms the diagnosis by revealing the characteristic features mentioned above.
Treatment and Prognosis
Treatment of APSGN is primarily supportive, focusing on the management of symptoms such as hypertension and edema. Antihypertensive medications and diuretics are commonly used. Antibiotics may be prescribed to eradicate any remaining streptococcal infection, although they do not alter the course of nephritis. The prognosis for APSGN is generally good, especially in children, with most patients recovering completely. However, some may experience persistent proteinuria or hypertension.
Conclusion
Acute post streptococcal glomerulonephritis is a classic example of an immune-mediated renal disease following an infectious trigger. Understanding its histological characteristics and pathogenesis is crucial for accurate diagnosis and management. While the condition is usually self-limiting, recognizing the signs and providing appropriate supportive care can significantly improve patient outcomes.
