A 44-year-old man was hospitalized because of exertional
dyspnea that had progressed for one month. A chest
X-ray film showed bilateral small nodular and reticular shadows. The patient presented with a positive inflammatory reaction and
hypoxemia. Bronchoalveolar davage fluid had a high lymphocyte fraction and a low CD4/CD8 ratio. Trichosporon cutaneum
antibodies were detected, and a specimen obtained by transbronchial lung biopsy showed alveolitis with
granuloma formation. The patient reacted positively on a provocation test that was done by having him stay home for 5 days.
Summer-type hypersensitivity pneumonitis was diagnosed, and a
steroid was administered because of the prolonged abnormal chest roentgenographic findings. KL-6, a mucinous high-molecular-weight
glycoprotein that is expressed on Type II pneumonocytes, was retrospectively used as a marker of
pneumonitis. A new kit for
enzyme-linked immunoassay (ED046) was used to measure the serum KL-6 level. The serum KL-6 level peaked approximately 10 days after the patient was admitted to the hospital and was thus kept away from
antigens, and also after the provocation test. The
steroid treatment was started, the KL-6 level decreased gradually. Within 2 months after
steroid treatment began, the dose of the
steroid was reduced and the KL-6 level decreased below the upper limit of normal. The KL-6 level remained low thereafter; it was not influenced by
liver dysfunction or other inflammatory processes. However, the
C-reactive protein level decreased rapidly after provocation and thereafter immediately returned to almost zero. The
lactate dehydrogenose level peaked 8 days after provocation and decreased rapidly after
steroid treatment. These results suggest that the serum KL-6 level provides new information regarding the
clinical course and treatment of
interstitial pneumonia. In addition KL-6 may be useful form monitoring disease activity, especially while tapering the dose of
steroids in patients with
interstitial pneumonia.