Microscopic polyangiitis initially presenting with idiopathic pulmonary fibrosis: a case report

Area of Science:

• Rheumatology
• Pulmonology
• Nephrology

Background:

• Microscopic polyangiitis (MPA) frequently involves the lungs, presenting as interstitial lung disease (ILD).
• Usual interstitial pneumonia is a common manifestation of MPA-associated ILD.
• Patients may initially present with pulmonary fibrosis, mimicking idiopathic pulmonary fibrosis (IPF).

Observation:

• A patient presented with fever of unknown origin, microscopic hematuria, and renal insufficiency.
• The patient had been treated for presumed idiopathic pulmonary fibrosis (IPF) with antifibrotic medication for nearly a decade.
• Antineutrophil cytoplasmic antibody (ANCA) testing was positive.

Findings:

• The patient was diagnosed with microscopic polyangiitis (MPA) based on clinical presentation and positive ANCA.
• Delayed diagnosis of MPA occurred due to initial misdiagnosis as IPF.
• Treatment with glucocorticoids and immunosuppressants led to symptom improvement.

Implications:

• This case underscores the importance of considering ANCA-associated vasculitis in patients with unexplained pulmonary fibrosis and systemic symptoms.
• Early and accurate diagnosis of MPA is crucial to prevent irreversible organ damage.
• Comprehensive diagnostic workup, including serological testing, is essential for differentiating MPA-ILD from IPF.