A 28-year-old man from North India presents with sudden onset hematuria, mild hypertension (148/92 mmHg), and periorbital edema 10 days after a throat infection. Urinalysis shows dysmorphic RBCs, RBC casts, and proteinuria (1.2 g/day). Serum creatinine is 1.1 mg/dL, and complement C3 levels are low. A diagnosis of post-infectious glomerulonephritis (PIGN) is made. Which of the following is NOT a typical feature of acute nephritic syndrome in PIGN?

Explanation

## Acute Post-Infectious Glomerulonephritis (PIGN) — Clinical Features ### Typical Presentation of Nephritic Syndrome in PIGN **Key Point:** Acute nephritic syndrome is characterized by the **nephritic triad**: hematuria (dysmorphic RBCs, RBC casts), hypertension, and mild-to-moderate proteinuria — NOT nephrotic-range proteinuria. ### Proteinuria Pattern in PIGN | Feature | PIGN (Nephritic) | MPGN / Membranous (Nephrotic) | |---------|------------------|-------------------------------| | **Proteinuria level** | <3 g/day (sub-nephrotic) | >3.5 g/day | | **Hematuria** | Dysmorphic RBCs, RBC casts | Absent or mild | | **Hypertension** | Common, due to fluid retention | Less prominent | | **Edema** | Periorbital, mild | Generalized, severe | | **Serum albumin** | Normal or mildly low | Markedly low (<2.5 g/dL) | **High-Yield:** Nephrotic-range proteinuria (>3.5 g/day) is the hallmark of nephrotic syndrome, NOT nephritic syndrome. In acute PIGN, proteinuria is typically **sub-nephrotic** (0.5–3 g/day), with dysmorphic RBCs and RBC casts being the dominant urinary findings. ### Why Other Options Are Correct Features of PIGN 1. **Hypertension due to sodium and fluid retention** — ✓ Common in acute PIGN; driven by reduced GFR and activation of RAAS. 2. **Dysmorphic RBCs and RBC casts** — ✓ Hallmark of glomerular hematuria; indicates active glomerulonephritis. 3. **Mild to moderate elevation in serum creatinine with preserved GFR initially** — ✓ Typical; creatinine may rise 30–50%, but GFR is preserved in most cases; severe renal failure is rare. ### Clinical Pearl **Nephritic vs. Nephrotic distinction:** If a patient with acute glomerulonephritis presents with nephrotic-range proteinuria, consider alternative diagnoses such as membranoproliferative GN, lupus nephritis, or IgA nephropathy with heavy proteinuria — not simple post-infectious GN. [cite:Harrison 21e Ch 297]