A patient presents with respiratory symptoms i.e. a cough, hemoptysis and glomerulonephritis. His C-ANCA levels in serum were found to be raised. The most likely diagnosis is -
Renal and pulmonary symptoms with positive c-ANCA suggest the diagnosis of Wegener's glomerulonephritis (see above explanation).
The clinical syndrome of Wegener's granulomatosis may be very similar to classical PAN or microscopic polyangiitis.
Following facts will help you to differentiate Wegener's granulomatosis from other Two -

Wegener's granulomatosis Vs classical PAN

Wegener's granulomatosis involves small vessels (arteriole, venule, capillary), while PAN involves medium size vessels.
Wegener's granulomatosis is associated with c-ANCA, while classical PAN is not associated with ANCA.
In Wegener's granulomatosis there is lung involvement, but not in classical PAN.
In Wegener's granulomatosis, there is glomerulonephritis (hematuria) without hypertension, while in classical PAN there is hypertension without glomerulonephritis.
In Wegener's granulomatosis, there is granuloma formation, while it is absent in classical PAN.
Classical PAN shows microaneurysms which are absent in Wegener's granulomatosis.


Wegner's granulomatosis Vs microscopic polyangiitis

Wegener's granulomatosis is associated with c-ANCA, while MPA is associated with p-ANCA.
Granuloma formation occurs in Wegener's granulomatosis, not in MPA.
Lung cavities and nodules are seen in Wegener's granulomatosis, but not in MPA.
Goodpasteur's syndrome
Classic polyarteritis nodosa
Wegener's granulomatosis
Kawasaki syndrome