This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Urinary tract, Subject name: Pathology
True regarding IgA nephropathy is 
Select and explain. 
A. Usually seen in children <10 years of age, B. Microscopic hematuria is common presentation, C. Recurrent gross hematuria following respiratory infections, D. Decreased serum IgA
C: Recurrent gross hematuria following respiratory infections
Answer: C: Recurrent gross hematuria following respiratory infections 
Explanation: IgA nephropathy, characterized by mesangial deposits of IgA-containing immune complexes, is the most common cause of the nephritic syndrome worldwide; it is also a common cause of recurrent hematuria; it commonly affects children and young adults and has a variable course. Ref: Robbins basic book of pathology 9th edition page 531 The clinical picture is usually characterized by recurrent bouts of haematuria that are often precipitated by mucosal infections. Mild proteinuria is usually present and occasionally nephrotic syndrome may develop. Ref: HARSH MOHAN TEXTBOOK OF PATHOLOGY 6th ed. pg no: 674 Histologically, the lesions in IgA nephropathy vary considerably.The glomeruli may be normal or may show mesangial widening and segmental inflammation confined to some glomeruli (focal proliferative GN); diffuse mesangial proliferation (mesangioproliferative GN); or (rarely) ove crescentic GN. The characteristic immunofluorescence picture is of mesangial deposition of IgA, often with C3 and properdin and smaller amounts of IgG or IgM. Ref: Robbins basic pathology 9th edition page 530