Microscopic polyangiitis with isolated cardiopulmonary involvement: A case report

Microscopic polyangiitis (MPA), a subtype of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis, is typically characterized by renal impairment but can present in atypical forms. This case underscores an unusual manifestation of MPA, involving solely cardiopulmonary pathology, thereby highlighting the necessity for increased clinical vigilance even in the absence of renal involvement.

An 87-year-old female patient with atrial fibrillation, hypertension, and type 2 diabetes presented with progressive chest tightness, bilateral limb and facial edema, and fatigue over 3 months. Initial evaluations suggested pneumonia accompanied by heart failure. However, standard treatment provided only temporary symptomatic relief.

Laboratory tests indicated that the level of myeloperoxidase ANCA reached 122 RU/mL. High-resolution computed tomography of the chest revealed characteristic findings of interstitial pneumonia, including thickening of lung lobular septa, bilateral ground-glass opacities, and pleural effusion, while other indicators did not suggest renal impairment. As a result, based on the 2022 American College of Rheumatology/European League Against Rheumatism standards, the final diagnosis was MPA.

The patient was given 80 mg of intravenous methylprednisolone daily for 3 days, then the dose was reduced to 60 mg daily for another 3 days. Afterwards, the patient was switched to oral prednisone 40 mg daily combined with 0.5 g of mycophenolate mofetil twice daily, and responded well to the treatment.

On the 6th day of hospitalization, the patient was discharged without complications. Follow-up blood tests that conducted 3 weeks post-discharge indicated normal liver and kidney function. A chest computed tomography scan revealed substantial resolution of bilateral pleural effusion. The majority of ground-glass opacities had resolved, with only a few persisting, primarily in the peripheries of the lobes.

This case suggests that MPA may present with isolated cardiopulmonary involvement as the initial manifestation without typical renal damage. Clinicians should consider MPA in patients with refractory interstitial pneumonia, pleural effusion, and myeloperoxidase ANCA positivity. Early immunosuppressive therapy may reverse organ damage and improve outcomes.