A patient presents with symptoms of cough, hemoptysis, and glomerulonephritis. His C-ANCA levels in serum were found to be raised. The most likely diagnosis is
First, I remember that C-ANCA is related to anti-neutrophil cytoplasmic antibodies. Wait, C-ANCA targets proteinase 3 (PR3), right? And it's commonly seen in Wegener's granulomatosis, now called granulomatosis with polyangiitis (GPA). GPA is a type of vasculitis that affects the upper respiratory tract, lungs, and kidneys. The triad mentioned here—cough, hemoptysis (which points to lung involvement), and glomerulonephritis (kidney involvement)—fits GPA.
Now, the other options. Let's see. P-ANCA is associated with other conditions like microscopic polyangiitis or Churg-Strauss syndrome. But the question specifies C-ANCA, so those are out. Goodpasture's syndrome also has pulmonary and renal symptoms, but it's due to anti-GBM antibodies, not ANCA. And systemic lupus erythematosus (SLE) can have glomerulonephritis but usually with positive ANA and other autoimmune markers, not C-ANCA.
So the key here is the combination of C-ANCA, lung, and kidney involvement. The clinical pearl is that C-ANCA is a hallmark for GPA, especially when there's upper/lower respiratory and renal involvement. The patient's presentation matches that.
**Core Concept**
The question tests the association between C-ANCA (cytoplasmic anti-neutrophil cytoplasmic antibodies) and granulomatosis with polyangiitis (GPA), a systemic vasculitis affecting the respiratory tract and kidneys. C-ANCA targets proteinase 3 (PR3) and is diagnostic of GPA, which presents with pulmonary and renal involvement.
**Why the Correct Answer is Right**
Granulomatosis with polyangiitis (GPA), formerly Wegener’s granulomatosis, is a necrotizing granulomatous vasculitis of small vessels. It classically involves the upper/lower respiratory tract and kidneys. C-ANCA positivity (targeting PR3) is a hallmark, correlating with active disease. Hemoptysis from lung involvement and glomerulonephritis from renal vasculitis are key clinical features. Pathogenesis involves ANCA-mediated neutrophil activation, leading to tissue destruction via oxidative and proteolytic pathways.
**Why Each Wrong Option is Incorrect**
**Option A:** Microscopic polyangiitis (MPA) is P-ANCA positive (anti-MPO) and lacks granulomatous inflammation, with predominant cutaneous and renal involvement.
**Option B:** Goodpasture’s syndrome involves anti-glomerular basement membrane (anti-GBM) antibodies, not ANCA, and presents with pulmonary hemorrhage and rapidly progressive glomerulonephritis.
**Option C:** Systemic lupus erythematosus (SLE) causes lupus nephritis but is associated with ANA, not C-ANCA, and has multisystem features like malar rash and arthritis.
**Clinical Pearl / High-Yield Fact**
C-ANCA (PR3) is