Acute glomerulonephritis is most classically associated with which preceding condition?

• A. Streptococcal infection
• B. Systemic lupus erythematosus
• C. IgA nephropathy
• D. Diabetic nephropathy

Answer: (A)

Post-streptococcal glomerulonephritis is a classic nephritic syndrome that follows a streptococcal infection. After a group A beta-hemolytic streptococcal throat or skin infection, the immune system forms antibodies that interact with streptococcal antigens to form immune complexes. These complexes deposit in the glomeruli, triggering inflammation and complement activation, which leads to hematuria, edema, hypertension, and sometimes reduced kidney function. The typical timing is a few weeks after the initial infection, and labs often show low C3 levels during the acute phase.

This pattern is why a preceding streptococcal infection is the best match. Other conditions can involve glomeruli but do not fit this classic post-infectious sequence: systemic lupus erythematosus can cause glomerulonephritis via autoimmune mechanisms; IgA nephropathy often presents with hematuria concurrent with mucosal infection rather than a delay after an infection; diabetic nephropathy is a chronic, gradual complication from long-standing hyperglycemia rather than an acute post-infectious event.