Serum complement (C3) level is characteristically NORMAL in which one of the following nephritic conditions?

• A Post-streptococcal glomerulonephritis
• B IgA nephropathy ✓
• C Lupus nephritis class IV
• D Membranoproliferative glomerulonephritis

Explanation

Complement is consumed by circulating or in situ immune complexes in post-infectious GN, lupus nephritis and MPGN, so B3 is persistently low in these diseases. In IgA nephropathy the alternative pathway activation is confined largely to the mesangium, and serum B3 remains normal, a standard discriminating point taught in Harrison and in Indian exam review texts. A persistently low B3 beyond 6 weeks also argues against post-streptococcal GN and suggests MPGN or lupus.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.