PE20.2 | Acute Post Streptococcal Glomerulonephritis — Summary & Reflection

KEY TAKEAWAYS

Acute post-streptococcal glomerulonephritis is a prototype immune-complex GN caused by nephritogenic strains of Group A beta-haemolytic Streptococcus. It follows throat infection (latent 1–2 weeks) or skin infection (latent 3–6 weeks), predominantly affecting children aged 5–15 years. The clinical syndrome is nephritic: cola-coloured haematuria, periorbital oedema, hypertension, and oliguria. The diagnostic signature is low C3 with normal C4 (alternative complement pathway), RBC casts on urine microscopy, and elevated ASO (throat infection) or anti-DNase B (skin infection). C3 normalises within 6–8 weeks; persistence beyond this window prompts renal biopsy. Management is supportive — penicillin to eliminate GAS, diuretics for fluid overload, antihypertensives (IV agents for encephalopathy), and dialysis if acute renal failure is severe. Corticosteroids have no role. The prognosis in children is excellent: over 95% recover completely.

REFLECT

Return to the 9-year-old boy in the hook. His complement results come back: C3 = 28 mg/dL (low), C4 = 24 mg/dL (normal). His ASO titre is elevated at 480 IU/mL. His urine microscopy shows dysmorphic red cells and 2–3 RBC casts per high-power field. (1) Does this fit the APSGN diagnosis? Which features confirm it and which — if any — are atypical? (2) His BP is 160/105 mmHg and he develops a severe headache. What is the risk, and what is your next management step? (3) If his C3 remains low at 12 weeks, what would you do and what alternative diagnoses would you consider?