OBJECTIVE: KL-6 is reported to be excreted from the lung alveolar and bronchial epithelial cells and may be a good marker for monitoring disease activity of interstitial pneumonia. This study was designed to ascertain the clinical significance of serum KL-6 levels in interstitial pneumonia associated with anti-neutrophil cytoplasmic antibody (ANCA)-related vasculitis.

METHODS: Serum KL-6 levels were determined by an enzyme-linked immunosorbent assay.

PATIENTS: We examined 20 healthy subjects, 13 patients with perinuclear (myeloperoxidase, MPO) ANCA-related vasculitis and 12 dermatomyositis (DM)/polymyositis (PM) patients as disease controls in this study. Six out of 13 patients with ANCA-related vasculitis had interstitial pneumonia.

RESULTS: Serum levels of KL-6 in ANCA-positive patients with interstitial pneumonia were significantly elevated, while they remained as low as those of healthy subjects in ANCA-positive patients without interstitial pneumonia. Similarly, KL-6 levels in sera were higher in 12 dermatomyositis/polymyositis patients with interstitial pneumonia, while they remained low in DM/PM patients without interstitial pneumonia. Moreover, the elevated serum KL-6 level was reduced during the convalescence induced by glucocorticoid therapy and reflected the disease activity of interstitial pneumonia associated with ANCA-related vasculitis.

CONCLUSION: These data suggest that the measurement of serum KL-6 levels may be a good monitoring system for the diagnosis and follow-up of interstitial pneumonia of patients with ANCA-related vasculitis.

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