Microscopic polyangiitis (MPA) may present with a syndrome that resembles idiopathic pulmonary fibrosis (IPF). We describe an MPA patient with the clinical presentation of a "pulmonary-muscle" syndrome in which interstitial lung disease antedated the onset of myopathy. Identification of vasculitis on muscle biopsy was instrumental in recognizing clinical, radiographic, and histopathologic features that were more characteristic of MPA than of IPF. Institution of glucocorticoid and cyclophosphamide therapy led to the induction of a complete remission. The histologic findings in this case implicate subclinical episodes of alveolar hemorrhage as the mechanism of interstitial lung disease in MPA.

Microscopic polyangiitis.Presse Med. 2007 May;36(5P2):895-901. Epub 2007 Mar 12.

Microscopic polyangiitis was initially considered a "microscopic" form of polyarteritis nodosa and was not definitively distinguished from it until the Chapel Hill nomenclature (1994). Microscopic polyangiitis is a systemic necrotizing vasculitis of small vessels. Its typical clinical manifestations are rapidly progressive glomerulonephritis and alveolar hemorrhage. Other possible symptoms resemble those encountered in polyarteritis nodosa. Microscopic polyangiitis belongs to the group of ANCA-associated vasculitides, and 75-80% of patients have pANCA to myeloperoxidase (MPO). Anti-MPO ANCA pathogenicity has been established in animal models, and a recent report describes transplacental transfer of these antibodies in humans, resulting in pulmonary hemorrhage and renal involvement in the newborn. Patients with no poor prognostic factors, as defined by a five-factor score, can be treated with corticosteroids alone, with immunosuppressants added only in case of treatment failure. Patients with one or more poor prognostic factors must receive a combination of corticosteroids and immunosuppressants, mainly intravenous pulsed cyclophosphamide, with plasma exchange as an adjuvant therapy for those with severe renal involvement. Once remission is achieved, maintenance therapy can replace cyclophosphamide by azathioprine or methotrexate. Biological therapies are under evaluation. The remission rate is above 80% with these regimens, and the relapse rate is around 30% at 5 years, lower than for Wegener's granulomatosis.

Microscopic polyangiitis associated with primary biliary cirrhosis: a causal or casual association?J Rheumatol. 2006 Nov;33(11):2351-3.

The association between microscopic polyangiitis (MPA) and primary biliary cirrhosis (PBC) has seldom been reported. We describe a patient with PBC and MPA who presented with polyarthritis and pulmonary nodules followed by pauci-immune crescentic glomerulonephritis and liver dysfunction. Detection of p-ANCA, antimyeloperoxidase, and antimitochondrial antibodies along with liver and renal histopathology allowed a diagnosis of MPA and PBC. We also discuss 2 other cases that could be unrecognized associations of both diseases. Further reports are necessary to clarify if the coexistence between PBC and MPA is causal or casual.

Increased serum vascular endothelial growth factor levels in microscopic poly angiitis with pulmonary involvement.Respir Med. 2006 Oct;100(10) : 1724-33. Epub 2006 Mar 20.

Microscopic polyangiitis (MPA) is a systemic necrotizing vasculitis that affects small vessels, resulting in a wide spectrum of organ involvement including the lungs. However, there are little serological markers that predict its prognosis or severity of pulmonary involvement. Vascular endothelial growth factor (VEGF) is an angiogenic mediator, which has been reported to be elevated in systemic vasculitis. In this study, we measured serum VEGF levels in 22 MPA patients with pulmonary involvement. We also investigated VEGF expression in pulmonary cells using flow cytometry analysis. We found that serum VEGF levels in MPA patients were significantly higher than those in respiratory or urinary tract infection. The serum VEGF levels decreased in parallel with the improvement of MPA symptoms. The serum VEGF levels in MPA patients who died within 5 years were significantly higher than those who survived more than 5 years. The sensitivity of VEGF levels to distinguish MPA patient with poor prognosis from those with good prognosis was 90.9%, and specificity was 81.8% (cutoff value = 802.5 pg/ml). The serum VEGF levels showed significant positive correlation with the composite physiological index, which indicates the severity of pulmonary lesion. In flow cytometry analysis, CD11b positive bronchoalveolar lavage fluid cells expressed VEGF. Immunohistochemically, alveolar macrophages, tissue infiltrating inflammatory cells and alveolar epithelial cells stained positive for VEGF. Measurement of serum VEGF levels in MPA might become one of the markers for prognosis and the severity of pulmonary involvement in MPA. VEGF might contribute to the development of pulmonary lesion of MPA.

Childhood microscopic polyangiitis associated with MPO-ANCA.Pediatr Nephrol. 2006 Jan;21(1):46-53. Epub 2005 Oct 27.

We reviewed the clinical, histological and serological parameters of microscopic polyangiitis (MPA) associated with antineutrophil cytoplasmic antibodies (ANCA) specific to myeloperoxidase (MPO). Six girls and one boy aged 12.0+/-2.6 years (7-15 years) met the following inclusion criteria: (1) clinical manifestations of systemic small vessel involvement; (2) histological demonstration of pauci-immune necrotizing glomerulonephritis; and (3) serological findings of increased concentration of MPO-ANCA by ELISA test. The main clinical manifestations were: influenza-like symptoms (100%), hematuria/proteinuria (100%), purpura (100%), pulmonary-renal syndrome (57%), acute renal failure (ARF) (29%), ischemic cerebral insults (29%), and necrotizing vasculitis of the skin (29%). All patients underwent renal biopsy examined by immunohistochemistry with expression of alpha-smooth muscle actin (alpha SMA) in glomerular and interstitial spaces. Patients were followed from 6 months to 5.5 years (35.4+/- 23.2 months). None of the patients died. Two of seven children who had ARF progressed to end stage renal disease; one developed chronic renal failure, and four normalized renal function. ARF and central nervous system involvement at presentation were parameters of poor renal outcome. A high score of fibro-cellular glomerular crescents was associated with worse prognosis. Early treatment enables a favorable prognosis of MPO-ANCA-associated MPA in children.

Development of microscopic polyangiitis in patients with chronic airway disease. Lung. 2005 Jul-Aug;183(4):273-81.

Microscopic polyangiitis (MPA) is a rare systemic vasculitis syndrome, which is often accompanied by positive myeloperoxidase-specific antineutrophil cytoplasmic antibody (MPO-ANCA). While pulmonary involvement of MPA consists mainly of diffuse alveolar hemorrhage and interstitial pneumonia, bronchiectasis has been reported as a pulmonary lesion in association with MPA. To investigate the clinical features of patients with MPA, focusing on the presence or the absence of preceding chronic airway diseases (CAD), we conducted a retrospective observational study of 26 patients in the last 13 years at Saga University Hospital. The clinical records and radiologic chest examinations were reviewed retrospectively. Pulmonary manifestations were alveolar hemorrhage in 3 patients (12%) and interstitial pneumonia in 5 (19%). Bronchiectasis, defined by the findings of chest radiograph and computed tomography, was found in 9 patients (35%). Four patients (15%) with bronchiectasis and one patient (4%) with chronic bronchitis had experienced chronic bronchial suppuration prior to the onset of MPA. Ten patients were classified as having chronic airway disease (CAD) before the onset of MPA. MPO-ANCA tended to be lower in the CAD group than in the non-CAD group. None of the patients in the CAD group had pulmonary hemorrhage or interstitial pneumonia. Only one patient (10%) in the CAD group died within 90 days of the onset of MPA, while 7 (43.8%) of the non-CAD group died. Our study suggests that MPA may result in part from CAD and that the clinical course of MPA with CAD may be different from MPA without CAD.

Pulmonary involvement in microscopic polyangiitis.Curr Opin Pulm Med. 2005 Sep;11(5):447-51.

PURPOSE OF REVIEW: Microscopic polyangiitis is a systemic necrotizing vasculitis that affects small vessels, resulting in a wide spectrum of organ involvement including the kidneys and the lungs. This paper reviews recent insights and observations into the pathogenesis, clinical manifestations, and treatment of pulmonary involvement in microscopic polyangiitis. RECENT FINDINGS: The spectrum of clinical presentations ranges from antecedent interstitial fibrosis to frank hemoptysis secondary to capillaritis. Computerized tomography imaging reveals a variety of pulmonary findings, including ground-glass attenuation, consolidation, thickening of bronchovascular bundles, and honeycombing. Antineutrophil cytoplasmic antibodies are important in diagnosis as well as in the pathogenesis and prognosis of microscopic polyangiitis. There is more evidence to support the various therapeutic modalities currently used in pulmonary manifestations of microscopic polyangiitis, including induction therapy with cyclophosphamide, the use of other novel pharmacologic agents such as the tumor necrosis factor-alpha blockers and rituximab, and nonpharmacologic modalities such as plasmapheresis and ventilatory management. SUMMARY: The pulmonary manifestations of microscopic polyangiitis are diverse and often difficult to manage; however, as our understanding and experience grows so does our ability to successfully diagnose and treat these patients.

Microscopic polyangiitis.Semin Respir Crit Care Med. 2004 Oct;25(5):523-33

Microscopic polyangiitis is a systemic vasculitis affecting smal-l and medium-sized vessels and is characteristically associated with a focal and segmental necrotizing glomerulonephritis. It may present as a pulmonary-renal syndrome with rapidly progressive glomerulonephritis and alveolar hemorrhage, but the pattern of disease will vary according to the organ systems involved. Granulomatous disease of the upper or lower respiratory tract is not a feature, and its presence suggests the diagnosis of Wegener's granulomatosis. The etiology of the condition is unclear, but most patients have antineutrophil cytoplasm antibodies (ANCA) with specificity for either myeloperoxidase (MPO) or proteinase 3 (PR3), and there is increasing evidence that these may be pathogenic. Current treatment includes an induction phase using cyclophosphamide and steroids to attain remission, followed by a maintenance phase in which the levels of immunosuppression are gradually reduced. Azathioprine may be substituted for cyclophosphamide at 3 months. Adjunctive plasma exchange or intravenous methylprednisolone is used in the management of either or both severe renal disease and alveolar hemorrhage, and new evidence suggests that plasma exchange is more effective in recovery of renal function. Overall, 1-year survival in systemic vasculitis is around 85%, and up to 50% of patients relapse, although relapse is less common in those with MPO-ANCA. Newer therapies are being explored in an attempt to increase the efficacy and reduce the toxicity of treatment.

Microscopic polyangiitis associated with diffuse panbronchiolitis.Intern Med. 2004 Apr;43(4):331-5.

There are several case reports of systemic vasculitis associated with chronic suppurative lung diseases. We describe a 46-year-old female, previously diagnosed as having diffuse panbronchiolitis (DPB), presenting with hemosputum and dyspnea. Her serum titer of MPO-ANCA was positive together with a high titer of BPI-ANCA. Chest X-ray and chest CT scan showed pulmonary hemorrhage, and the renal biopsy specimen revealed necrotizing, crescentic glomerulonephritis. She was diagnosed as having ANCA-associated vasculitis, and more specifically, microscopic polyangiitis accompanied by DPB. She was treated with methylprednisolone pulse therapy, followed by intravenous cyclophosphamide. This case suggested a possible association with chronic bacterial infection, which may play a role in the pathogenesis of ANCA-associated vasculitis.

Antineutrophil cytoplasmic antibody(ANCA).Rinsho Byori. 2003 Jul;51(7): 644-8.

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(WG) than the other primary vasculitides. MPO-ANCA can be found in microscopic polyangiitis (MPA), Churg Strauss Syndromes(CSS), drug-induced vasculitis, and environmental factor-induced such as silicosis vasculitis more frequently than WG. The value of the IIF test for ANCA detection can be greatly increased by the addition of a standardized antigen-specific ELISA. The intra-assay and inter-assay CV of the MPO and PR-3 ELISA were 6.6 to 4.8%, respectively. Close ANCA titer correlation was shown between MPO-ANCA ELISA and the activity of ANCA associated vasculitis. Renal manifestations and pulmonary manifestations are observed in 70-90% of AAV as the initial manifestation. The changes in titers of ANCA seem to reflect disease activity in 60-70% of AAV patients. A combination of steroids and immunosuppressive drugs is effective in relieving the clinical symptoms of AAV.

Pulmonary interstitial fibrosis as a presenting manifestation in perinuclear antineutrophilic cytoplasmic antibody microscopic polyangiitis. Chest. 2003 Jan;123(1):297-301.

Microscopic polyangiitis (MPA) is one of the vasculitides that is included in the pulmonary renal syndromes. Pathologically, MPA has been defined as necrotizing vasculitis with few or no immune deposits, primarily affecting small vessels including arterioles, venules, or capillaries. Pulmonary interstitial fibrosis (PIF) as an accompanying manifestation in MPA has not been widely appreciated. In the present study, we report six cases of MPA at our institution with radiographic evidence of PIF that was apparent before any treatment was administered. All had biopsy evidence of renal disease that was consistent with MPA as well as positive serum perinuclear antineutrophilic cytoplasmic antibody titers. Hemoptysis was observed in approximately one half of the patients. As determined by CT of the chest, PIF was detected in all of the patients and was often present years before a diagnosis of MPA was made. We conclude that PIF may occur as a pulmonary manifestation of MPA. Further appreciation of this finding may lead to more data with respect to the incidence of PIF in MPA, and to a better understanding of the mechanisms that are involved in the development of this finding.

Two patients with microscopic polyangiitis and unusual pulmonary manifestation.Respirology. 2002 Mar;7(1):73-6.

We encountered two patients with microscopic polyangiitis (MPA) associated with unusual pulmonary manifestations. The first patient was a 45-year-old man who had worked in amine for 3 years when he was young. On admission, chest X-rays showed long-standing silicosis and a new patchy infiltration. The second patient was a 52-year-old female. On admission, chest X-rays showed bilateral patchy infiltrations. Since then, variable patterns of patchy infiltration have waxed and waned repeatedly. The renal biopsy revealed that both patients had glomerulonephritis associated with small vessel vasculitis but with few or no immune deposits. There was neither granulomatous inflammation nor eosinophilic infiltration. Myeloperoxidase-antineutrophil cytoplasmic antibody (ANCA) was positive in both patients. After treatment with glucocorticoids and cyclophosphamide, radiological findings were minimal and stable. These two cases show that patients with MPA have a wide spectrum of radiological findings.

Microscopic polyangiitis (microscopic polyarteritis).Semin Diagn Pathol. 2001 Feb;18(1):3-13.

Microscopic polyangiitis ("microscopic polyarteritis") is a form of necrotizing small vessel vasculitis that most often affects venules, capillaries, arterioles, and small arteries, although it occasionally involves medium-sized arteries. Microscopic polyangiitis is a more appropriate name than microscopic polyarteritis because some patients have no evidence for arterial involvement. The absence or paucity of immunoglobulin localization in vessel walls distinguishes microscopic polyangiitis from immune complex mediated small vessel vasculitis, such as Henoch-Schonlein purpura and cryoglobulinemic vasculitis. Clinical, epidemiological, and pathologic differences warrant the separation of microscopic polyangiitis from polyarteritis nodosa on the basis of involvement of capillaries and venules by the former but not the latter. Pauci-immune necrotizing and crescentic glomerulonephritis, and hemorrhagic pulmonary capillaritis are common in patients with microscopic polyangiitis. Microscopic polyangiitis is the most common cause for pulmonary-renal vasculitic syndrome. The vasculitis in patients with microscopic polyangiitis is pathologically indistinguishable from the vasculitis of Wegener's granulomatosis and Churg-Strauss syndrome. Granulomatous inflammation distinguishes Wegener's granulomatosis from microscopic polyangiitis. Asthma and eosinophilia distinguish Churg-Strauss syndrome from microscopic polyangiitis. Microscopic polyangiitis, Wegener's granulomatosis, and Churg-Strauss syndrome are all associated with circulating antineutrophil cytoplasmic autoantibodies.

Microscopic polyangiitis with alveolar hemorrhage. A study of 29 cases and review of the literature. Groupe d'Etudes et de Recherche sur les Maladies "Orphelines" Pulmonaires (GERM"O"P). Medicine (Baltimore). 2000 Jul;79(4):222-33.

Microscopic polyangiitis (MPA) is a systemic small-vessel vasculitis primarily associated with necrotizing glomerulonephritis and pulmonary capillaritis. In this retrospective study of 29 patients with MPA and alveolar hemorrhage (AH), we characterized the pulmonary manifestations at presentation and assessed the short- and long-term outcome. AH was diagnosed when bronchoalveolar lavage was macroscopically bloody, or contained hemosiderin-laden macrophages, in the absence of lung infection or pulmonary edema. MPA was diagnosed when AH was associated with focal segmental necrotizing glomerulonephritis at kidney biopsy or pathologically proved small-vessel vasculitis. There were 17 women and 12 men, with a mean age of 55.8 +/- 16.7 years. The onset was rapidly progressive, but in 8 (28%) patients, symptoms preceded the diagnosis for more than 1 year. The most constant systemic findings associated with AH were glomerulonephritis in 28 (97%) patients; fever (62%); myalgia and arthralgia (52%); weight loss (45%); ear, nose, and throat symptoms (31%); and skin involvement (17%). Lung opacities were bilateral in 26 (90%) patients, most frequently involving the lower part of the lungs. Bronchoalveolar lavage, performed in 27 patients, was hemorrhagic in 25 (93%), and contained numerous siderophages in others. Most patients were severely anemic (mean hemoglobin, 8.1 +/- 1.8 g/dL). ANCA, present in 27 (93%) patients, gave a perinuclear (14), cytoplasmic (11), or mixed (1) pattern. Mean serum creatinine level was 407 +/- 415 mumol/L. Renal biopsy confirmed the presence of necrotizing glomerulonephritis in 27 patients. Patients were treated with corticosteroids (100%), cyclophosphamide (79%), plasmapheresis (24%), dialysis (28%), and mechanical ventilation (10%). The overall mortality rate was 31% (9 patients). Deaths were related to vasculitis (5 patients) or side effects of treatment (4). Deaths were more frequent in aged or mechanically ventilated patients. The 5-year survival rate was 68%. The recovery of respiratory function among survivors was clinically considered complete in 20 (69%) patients. However, 7 patients (24%) had persistent alterations on pulmonary function tests. Of the 11 patients who had relapses, 2 died from AH.

Microscopic polyangiitis (microscopic polyarteritis) with late emergence of generalised Wegener's granulomatosis. Ann Rheum Dis. 1999 Oct;58(10): 644-7.

OBJECTIVES: Recent proposals for the nomenclature of systemic vasculitis have focused on a distinction between (classic) polyarteritis nodosa (PAN) and microscopic polyangiitis or polyarteritis (MPA). Thus, MPA may cause necrotising vasculitis of medium sized or small arteries but, unlike PAN, involvement of "microscopic" vessels must always be present in the former. This study aimed to show that the term "MPA" may represent a source of misinterpretation and to help illustrate difficulties of applying diagnostic criteria/definitions for conditions of unknown aetiology or variable clinical presentation and course. METHODS: Among 1250 consecutive patients screened for antineutrophil cytoplasmic antibodies (ANCA), 59 had been found to have idiopathic necrotising and crescentic glomerulonephritis plus ANCA while five had been found to have isolated pulmonary haemorrhage with biopsy verified necrotising alveolar capillaritis plus ANCA. None of these patients had clinical or histological evidence of Wegener's granulomatosis (WG) or evidence of biopsy verified vasculitis involving vessels other than glomerular or pulmonary capillaries at the time of presentation. RESULTS: Six of the 64 patients who met definition criteria for MPA at the time of initial diagnoses had entered into complete clinical remission upon appropriate corticosteroid and cyclophosphamide treatment between two weeks and three months, though subsequently (20 to 72 months; mean time: 42.3 months) developed characteristic clinical and histological features of overt WG. CONCLUSIONS: Microscopic polyangiitis/polyarteritis may be a dynamic condition with clinical and histopathological features evolving over time to other forms of small vessel vasculitis, mainly WG, thereby meaning that follow up would be necessary not only to control a given patient but also to make a final diagnosis. This follow up should be for a long time as there may be a long interval between initial presentation and subsequent development of WG lesions.

An autopsy case of MPO-ANCA-positive microscopic polyangiitis with manifestations of pulmonary hemorrhage and diffuse alveolar damage.Nihon Kokyuki Gakkai Zasshi. 1999 Oct;37(10):807-11.

A 68-year-old woman was admitted to our hospital because of fever of unknown origin and pain in the lower extremities. Six weeks after onset, diffuse infiltrative shadows were observed on chest X-ray films, and marked hypoxemia and progressive renal dysfunction suddenly developed. Corticosteroid therapy (2 courses of pulse therapy, each consisting of methylprednisolone at 500 mg/day for 3 days) was not effective, and the patient died 9 weeks after onset because of respiratory failure. Serologic tests were positive for MPO-ANCA. Histopathologic findings at autopsy disclosed arteriolar fibrinoid necrosis in tissues of the liver, spleen, lungs, and kidneys, thus yielding a diagnosis of microscopic polyangiitis. Lung specimens also demonstrated massive alveolar hemorrhaging in the mid-lung fields and diffuse alveolar damage (DAD) in all lobes. Pulmonary hemorrhage coexistent with DAD worsens the prognosis for microscopic polyangiitis in patients positive for MPO-ANCA.

Necrotizing alveolar capillaritis in autopsy cases of microscopic polyangiitis. Incidence, histopathogenesis, and relationship with systemic vasculitis.Arch Pathol Lab Med. 1997 Feb;121(2):144-9.

OBJECTIVES: To determine the incidence of necrotizing alveolar capillaritis, to elucidate its histopathogenesis and the most reliable histopathologic features for its detection, and to explore its relationship with systemic vasculitis in microscopic polyangiitis. METHODS: Twenty-five autopsy cases of microscopic polyangiitis were examined. Double staining with periodic acid-silver methenamine and trichrome was used. RESULTS: Periodic acid-silver methenamine and trichrome staining proved to be a useful and convenient method for the detection of necrotizing alveolar capillaritis. Capillaritis was detected in 10 (40%) of the 25 cases studied. Of 18 cases that exhibited the early degenerative stage of systemic vasculitis, capillaritis was seen in 10 (56%). Fibrinoid necrosis of the alveolar wall was the most reliable histopathologic feature for detecting necrotizing alveolar capillaritis in microscopic polyangiitis. The early stage of capillaritis displayed very little neutrophil exudation, and conspicuous accumulation of neutrophils developed after fibrinoid necrosis. Statistical analysis revealed that alveolar capillaritis had a statistically significant correlation (P < .05) with necrotizing vasculitis of the pulmonary circulatory system. Capillaritis tended to occur when systemic vasculitis of microscopic polyangiitis was in its early degenerative stage. CONCLUSION: Necrotizing alveolar capillaritis was detected in about half of the microscopic polyangiitis autopsy cases that exhibited the early degenerative stage of systemic vasculitis, and results based on earlier reports of clinical observations may have been too conservative.

Microscopic polyangiitis and pulmonary fibrosis in a patient who died of Candida pneumonia and intra-alveolar hemorrhage.Nihon Kyobu Shikkan Gakkai Zasshi. 1997 Aug;35(8):915-20.

A 74-year-old man was admitted to our hospital because of edema of the lower legs, fever, and increasing fatigue. Laboratory evaluation revealed proteinuria, microhematuria, leukocytosis, thrombocytosis, anemia, a high level of C-reactive protein. A test for myeloperoxidase-antineutrophil cytoplasmic antibodies was highly positive. Microscopic polyarteritis nodosa was diagnosed and therapy with prednisolone was begun. Examination of a renal biopsy sample showed necrotizing crescentic glomerulonephritis. A chest roentgenogram and CT scan disclosed bilateral basilar interstitial changes. Six months later, the patient was admitted again because of disturbance of consciousness, malnutrition, and hyponatremia. After admission, alveolar infiltrates developed in the right lung and the patient died on the 5th hospital day as a result of respiratory failure. An autopsy revealed Candida pneumonia of the right lung and massive intra-alveolar hemorrhage, which was believed to have caused the respiratory failure. Other findings were usual interstitial pneumonia, cellular small-vessel angiitis in the lungs, and healed angiitis in the kidneys and liver. In this case of microscopic polyangiitis and chronic interstitial pneumonia, steroid therapy was effective against the angiitis, but the patient died of an opportunistic infection and alveolar hemorrhage.

Progressive obstructive lung disease associated with microscopic polyangiitis.Am J Respir Crit Care Med. 1997 Feb;155(2):739-42.

Small airway involvement and progressive severe airflow obstruction are unexpected features in patients with microscopic polyangiitis. We report the case of a patient with microscopic polyangiitis and circulating anti-neutrophil cytoplasmic antibodies (ANCA), who developed pulmonary hyperinflation and airflow obstruction over a 7-yr period. Systemic manifestations of this vasculitis improved under corticosteriods and cyclophosphamid therapy, a treatment that did not influence either the very high level of anti-myeloperoxidase antibodies or the ventilatory impairment. Small airway involvement was suspected on the basis of pathologic small airway lesions and a mild emphysematous pattern on computed tomography (CT) scan, which was out of proportion with the severity of the obstructive lung disease.

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