Monitoring with serum SP-A, SP-D, and KL-6 in a patient with interstitial pneumonia complicated with ANCA-associated glomerulonephritis

A 69-year-old woman was admitted to hospital, complaining of fatigue and dry cough. Her renal function deteriorated rapidly, and the laboratory findings showed elevated myeloperoxidase-specific anti-neutrophil cytoplasmic antibody (ANCA). Renal biopsy examination revealed crescentic glomerulonephritis (pauci-immune type), and linear opacities and a honeycomb appearance in both lower lobes was evident on the chest computed tomography scan. The patient was diagnosed as having ANCA-associated glomerulonephritis complicated with mild interstitial pneumonia (IP). Treatment with methylprednisolone pulse therapy improved both her renal function and IP, but her lung lesions worsened during the course of tapering the prednisolone doses. After careful observation, her IP improved gradually without specific treatment. Worsening or improvement of her lung lesions was accompanied by changes in the serological markers of IP, namely, surfactant protein-A, surfactant protein-D, and KL-6. We found that monitoring these markers was helpful in diagnosing and managing IP in our patient with ANCA-associated vasculitis.