before initiation of UST treatment. Although the serum level of KL-6 as a marker of IP was high (2149 U/mL; normal range, 0-499), the patient had no clinical symptoms of respiratory disease. In addition, chest computed tomography (CT) (Fig. 1) showed no interstitial shadows such as shown in usual IP or a non-specific IP, and there was no consolidation in the lobe. After two administrations of UST, she developed a clinical symptom of a cough and the serum KL-6 was elevated to 6809 U/mL. The b-D-glucan was normal and systemic CT showed no malignancy in the internal body. A chest CT revealed consolidation shadows in both lobes. Respiratory physicians consulted about the symptom diagnosed IP. After discontinuation of UST, the consolidation shadows on the lung had diminished and KL-6 had decreased to the initial level. From these findings, we concluded the respiratory phenomenon was UST-induced IP.In case 2, a 60-year-old man had a 10-year history of psoriasis. Before administration of UST, IFX and cyclosporin had been used, however, they had been discontinued due to infusion reaction or insufficient efficacy. UST was then begun, and the initial serum KL-6 level was 1046 U/mL. He had no risk factor such as elderliness, diabetes mellitus or low albumin. After 2 years of treatment with UST, the serum KL-6 was elevated to 2149 U/mL. Systemic CT showed no malignancy in the internal body and chest CT showed consolidation shadows in the left lobe which a respiratory physician diagnosed as IP. Since the use of UST has been discontinued, the shadows have diminished and KL-6 has decreased to the initial level.Little is known regarding the mechanism of UST-induced IP. Although there are some reports of anti-TNF-a agent-induced IP, 3,4 it is difficult to prove that these agents actually cause this condition. In both cases, there were similar points of a high KL-6 level at the initiation of treatment with UST. We have treated approximately 200 patients who received UST. There were three patients showing KL-6 of more than 1000 ng/mL in patients who were treated within our institution. IP developed in two of them. After discontinuation of UST, at least a period of 6 months was needed to return to baseline in the level of KL-6. To detect the increase of KL-6, blood examination should be performed every 3 months during treatment.

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