A 25-year-old woman presents with recurrent macroscopic hematuria following upper respiratory tract infections (synpharyngitic hematuria) over 3 years. No proteinuria. Renal biopsy shows mesangial IgA deposits on immunofluorescence. Which Oxford MEST-C criterion is associated with the worst prognosis in IgA nephropathy?
- A Mesangial hypercellularity (M1)
- B Tubular atrophy/interstitial fibrosis involving >25% of cortex (T2) ✓
- C Segmental glomerulosclerosis (S1)
- D Endocapillary hypercellularity (E1)
Correct answer: B. Tubular atrophy/interstitial fibrosis involving >25% of cortex (T2)
Explanation
The Oxford MEST-C scoring system grades IgA nephropathy histologically. Tubular atrophy/interstitial fibrosis (T) has the strongest correlation with long-term renal outcome: T0 (<25% involvement), T1 (25-50%), T2 (>50%). T2 score is independently associated with the highest risk of renal failure and ESKD. S1 (segmental sclerosis) also predicts poor outcome. M and E scores have less predictive power for long-term decline than T scores. The VALIGA and TESTING studies have validated these criteria.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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