C4A and acute pyelonephritis: This is because recurrent or de-novo acute proliferative glomerulonephritis causing MVI can be differentiated by a constellation of clinical features and other investigations such as urine microscopy for hematuria, proteinuria, correlation with serum C3 and C4 levels, etc. Similarly, acute pyelonephritis in the post-transplant period can be distinguished by characteristic clinical features such as burning micturition, fever, etc., in addition to urine microscopy for pus cells, neutrophilic leucocytosis, and urine culture.