Pulmonary Pathology Online
Pathology of Pulmonary Vasculitis
granulomatosis (WG), microscopic polyangiitis (MPA) and Churg- Strauss
syndrome (CSS) are small to medium-vessel vasculitides that, because of
their frequent association with antineutrophil cytoplasmic antibodies (ANCA),
are usually referred to as ANCA-associated systemic vasculitides (AASV).
These diseases are challenging to diagnose and to treat. The diagnosis of AASV is made on the basis of clinical findings, biopsy of the involved organ and the presence of ANCA in the serum.
Lung disease is a very common and important clinical feature of AASV.
Vasculitis in the lung usually involves the small vessels -arteries, capillaries and venules.
Distinguishing the ANCA-associated vasculitides from other forms of vasculitis or nonvasculitic processes (such as infection) can be particularly difficult.
ANCA are associated with small sized vessel vasculitis ; one subtype is an antibody against myeloperoxidase (MPO), which stains in a perinuclear pattern (P-ANCA) indirect immunofluorescence (IIF) using a neutrophil substrate, and the other subtype is an antibody against proteinase-3(PR-3), which stains in a diffuse granular cytoplasmic pattern ANCA by IIF. PR-3 ANCA is more specific in Wegener's granulomatosis than the other primary vasculitides. MPO-ANCA can be found in microscopic polyangiitis (MPA), Churg Strauss Syndromes(CSS).
Capillaritis with severe pulmonary hemorrhage may be seen in all three diseases or as isolated single organ disease.
Of the other causes of small vessel vasculitis of the lungs SLE is the most frequent. Alveolar hemorrhage may be the presenting manifestations and is usually associated with glomerulonephritis. Immune complexes are present in the lungs with a granular distribution.
Less commonly, pulmonary capillaritis has been reported in patients with polymyositis and occasionally in the other collagen vascular diseases.
Pulmonary disease is uncommon in Henoch-Schonlein purpura and in the vasculitis of cryoglobulinanemia.
In Goodpasture’s syndrome primary capillaritis is associated with linear deposition of IgG and complement along the basement membrane.
The dual circulation of the lung may be one reason why the response to the systemic vasculitic disorders is unique, providing a spectrum of diseases different to that seen in other organs. Eg. The classical lesions of polyarteritis nodosa, which is a disease of systemic muscular arteritis, are very rarely seen in the lungs; whereas certain diseases such as Wegener’s granulomatosis typically involve the lower respiratory tract.
Recent classifications separate the types of vasculitis according to vessel size and type of immune response involved.
With rare exceptions, those that involve the lung cause disease of the small vessels - small muscular arteries, arterioles, capillaries, and venules. Some types of small vessel vasculitis in the lung are also frequently associated with glomerulonephritis, producing the "pulmonary-renal" syndromes.
Very rarely the elastic pulmonary arteries may be involved by giant cell arteritis or Takayasu arteritis.
In addition to small vessel disease, Behcet’s syndrome typically produces aneurysms of the large elastic pulmonary arteries.
The interpretation of biopsy material requires detailed information of the clinical, radiological and serological findings.
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