This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: miscellaneous, Subject name: Pathology
Rapidly progressive glomerulonephritis is characterized histologically by 
Select and explain. 
A. Fibromuscular hyperplasia of the renal aery, B. Crescents in the glomeruli, C. Neutrophils in the interstitium, D. Splitting of the basement membrane by mesangial cells
B: Crescents in the glomeruli
Answer: B: Crescents in the glomeruli 
Explanation: The finding of crescents within the Bowman's space of many glomeruli is diagnostic of rapidly progressive (crescentic) glomerulonephritis (RPGN). RPGN may be subdivided into three types based on the immunofluorescence (IF) staining pattern. Type I RPGN reveals linear staining of IgG and C3. The majority of these patients are found to have Goodpasture's disease (anti-GBM disease). Type II RPGN reveals immune complex deposition (granular staining). These patients may have other glomerular or systemic diseases, including post-streptococcal GN, membranoproliferative GN, IgA nephropathy (Berger's disease), and SLE. Type III RPGN reveals minimal immune changes and is referred to as pauci-immune crescentic GN. Antineutrophil cytoplasmic antibodies (ANCAs), which are found in some patients with vasculitis, are found in many of these patients with pauci-immune GN. ANCAs are either perinuclear (P-ANCAs, against myeloperoxidase) or cytoplasmic (C-ANCAs, against proteinase 3). P-ANCAs are found in patients with microscopic polyaeritis and idiopathic crescentic GN, while C-ANCAs are found in patients with Wegener's granulomatosis, a disorder that is characterized by acute necrotizing granulomas of the respiratory tract, focal necrotizing vasculitis, and diffuse necrotizing GN Reference: Robbins & Cotran Pathologic Basis of Disease, 9edition