Presentation of MPO-ANCA positive microscopic polyangiitis with usual interstitial pneumonia.

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Conference Proceeding

Publication Date


Publication Title

Am J Respir Crit Care Med


Microscopic polyangiitis (MPA), commonly associated with the myeloperoxidase (MPO) subtype, is a pauci-immune vasculitis of small vessels. Common manifestations include renal impairment, rash, mononeuritis multiplex, polyarticular arthritis, and diffuse alveolar hemorrhage. The incidence of interstitial lung disease (ILD) in MPO-anti-neutrophilic cytoplasmic antibody (ANCA) vasculitis is reported from 2.7% to 43%. We share a rare case of Usual Interstitial Pneumonia (UIP) preceding development of extra-pulmonary manifestations of MPA to emphasize the need for surveillance of extrapulmonary rheumatologic manifestations in patients with UIP radiologic pattern and positive autoantibodies. Case:A 75 year old female from Mexico, never smoker, was referred to pulmonology for a 6 week history of cough, 23 pound weight loss and interstitial infiltrates on chest x-ray. She denied dyspnea, Raynaud, joint pain or swelling, or rash. Pulmonary evaluation was remarkable for lack of hypoxia, presence of bibasilar crackles, normal forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1) and FEV1/FVC, and diffusion capacity (DLCO) 56% of predicted. Serology exposed an antinuclear antibody (ANA) 1:640 (speckled), rheumatoid factor 1230 with negative cyclic citrullinated peptide (CCP). High resolution CT showed peripheral reticulation and honeycombing (definite UIP pattern). The patient deferred rheumatologic evaluation. She presented 8 months later with livedo reticularis and bilateral foot numbness. DLCO decreased to 37% predicted. Perinuclear (P-) ANCA was positive, confirmed with MPO. Repeat CT chest exhibited areas of superimposed consolidation. Bronchoscopy revealed chronic inflammation consistent with focal organizing pneumonia without evidence of infection.EMG showed axonal sensorimotor peripheral neuropathy with muscle denervation. Sural nerve biopsy exhibited vasculitic neuropathy. The patient was diagnosed with MPA, MPO-ANCA subtype with vasculitic polyneuropathy and UIP. She was treated with systemic steroids and cyclophosphamide with improvement in her symptoms and stabilization of DLCO. Discussion:The incidence of rheumatologic disease developing in patients initially diagnosed with idiopathic pulmonary fibrosis (IPF) is up to 15.5% at 10 years. The addition of ANCA to the screening serology panel of ANA, CCP and rheumatoid factor, in patients with suspected IPF, has been suggested to identify patients with vasculitis. Early diagnosis may lead t0 closer monitoring and earlier treatment. Proposed mechanisms of development of ILD in MPA include 1) recurrent subclinical alveolar hemorrhage causing fibrosis and 2) oxidative stress caused by MPO-ANCA stimulating myeloperoxidase and producing hypochlorous acid damaging lung tissue. Response to treatment is variable in MPA with UIP, though prognosis and treatment response is better than in patients with IPF.



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