A 9-year-old boy had typical post-streptococcal glomerulonephritis with gross hematuria, low C3, and elevated anti-DNase B titers. He recovered clinically, but repeat testing at 12 weeks shows C3 remains persistently low while C4 is normal. The most appropriate interpretation is:

• A Expected finding, since C3 takes up to six months to normalize in post-streptococcal glomerulonephritis
• B Indication of progression to anti-GBM disease
• C Evidence of ongoing streptococcal infection requiring retreatment
• D Persistent hypocomplementemia suggesting an underlying alternative complement pathway disorder such as MPGN or C3 glomerulopathy ✓

Explanation

In classic post-streptococcal GN, serum C3 falls during the acute phase and returns to normal within six to eight weeks. Hypocomplementemia persisting beyond eight weeks should prompt evaluation for MPGN, C3 glomerulopathy, or factor H related dysregulation, conditions in which the classical pathway (hence C4) is spared. Anti-GBM disease does not cause hypocomplementemia because it is not an immune-complex process.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.