Subclinical interstitial lung abnormalities in stable renal allograft recipients in the era of modern immunosuppression

BACKGROUND: Interstitial lung abnormalities have been detected in up to 24% of kidney transplant patients receiving traditional immunosuppressive therapies (eg, cyclosporine, azathioprine); they usually occur early after transplantation and tend to resolve over time. Newer immunosuppressants such as mycophenolic acid and, particularly, mammalian target of rapamycin (mTOR) inhibitors (eg, sirolimus) may cause significant lung toxicity. However, the prevalence and severity of interstitial lung lesions in long-term, stable kidney transplant patients receiving either traditional or newer immunosuppressants is not known. METHODS: We conducted a prospective, cross-sectional study examining high-resolution lung computed tomography (CT) scans in 63 stable kidney transplant recipients whose immunosuppressive therapy had remained unchanged for over 24 months. We compared CT findings of patients taking newer (mycophenolic acid and mTOR inhibitors) and traditional (calcineurin inhibitors and azathioprine) immunosuppressive drugs. RESULTS: Interstitial lung alterations were observed in only 3/63 patients (4.8%); the prevalence was 11.5% (3/26) versus 0% (0/37) among the newer versus traditional immunosuppressive therapy groups, respectively (P = .065). The CT patterns were usual interstitial pneumonia and nonspecific interstitial pneumonia-like. The median time between transplant and CT was 49 months in the three patients with CT alterations and 95 months in the remaining 23 patients on newer immunosuppressants. It was 75 months for all patients on newer immunosuppressive drugs and 133 months for those on traditional therapies (P = .0015). A follow-up CT, performed in 2/3 patients with interstitial abnormalities, showed that the lesions were stable in one, while they had disappeared in the other. CONCLUSIONS: Interstitial lung abnormalities are infrequent and mild in stable kidney transplant patients treated with newer as well as traditional immunosuppressive drugs. As such abnormalities were detected in patients screened earlier after transplantation, the time since transplantation rather than the drug type is probably the major determinant.