This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nephritic & Nephrotic Syndrome, Subject name: Pediatrics
In a case of glomerulonephritis (GN) , C3 is normal in all the following except? 
Select and explain. 
A. Diffuse lupus nephritis, B. Good pasteur's syndrome, C. IgA nephropathy, D. HSP
A: Diffuse lupus nephritis
Answer: A: Diffuse lupus nephritis 
Explanation: Low C3 nephritis is observed in: Post-infectious GN, MPGN(Membranoproliferative GN) SLE Subacute bacterial endocarditis Cryoglobulinemia, shunt nephritis