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The average age of onset in this disorder is approximately 50 years. The course may be indolent before the diagnosis is made. Savage et al noted general symptoms including arthralgias or hemoptysis several months or years before the explosive phase of the disease microscopic polyangiitis, polyangitis, poliangitis. Most patients experienced some systemic symptoms before diagnosis of

Renal Involvement

Renal involvement is a major feature of MPA and is characterized by RPGN. Renal angiography results are usually normal, and the coexistence of vascular and glomerular nephropathy is

Pulmonary Involvement

Lung hemorrhage can also be observed in MPA: Hemoptysis may be the first sign of severe lung hemorrhage, which is characterized by dyspnea and anemia and may precede diffuse alveolar damage owing partially or completely to capillaritis. Diffuse alveolar damage and interstitial lung fibrosis can be present and should be considered a complication of the

Other Clinical Features

These are similar to those observed in PAN. Peripheral neuropathy, found in only 14% to 36% of the cases, is less frequent than in

Laboratory Findings

Nonspecific tests reflect the systemic inflammatory nature of the disease. HBsAg is negative in almost all patients. Impaired renal function with creatininemia greater than 120 mumol/L was present in all the patients reported by Savage et al. Microscopic hematuria is constant and proteinuria occurs in more than 90% of patients, often greater than 3 g per 24 hours. Renal histology is characterized by the presence of focal segmental thrombosing and necrotizing glomerulonephritis. Extracapillary proliferation forming crescents is present in nearly all renal biopsies and often affects more than 60% of the glomeruli. ANCA are detected in the majority of MPA patients, and most of these ANCA are p-ANCA (perinuclear staining pattern) antimyeloperoxidase, although c-ANCA (cytoplasmic staining patternanti-proteinase 3 can also be detected. Visceral angiography is usually normal and does not reveal