Clinical features of interstitial pneumonia associated with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) commonly affects the lungs. However, the incidence of interstitial pneumonia (IP) related to SLE was reported to be about 10%, less than in the case of other connective tissue diseases, and the mechanism via which IP is related to SLE remains to be elucidated.

We retrospectively reviewed the medical records and high-resolution computed tomography (HRCT) images of 69 SLE patients who were admitted to our hospital between January 2011 and December 2015.

Fifty-five of the patients were female (80%), and the mean age at the onset of SLE was 42.4 years. IP developed in 20 patients (29%), 14 of whom were female (70%), and the mean age at SLE onset was 53.4 years, significantly older than those without IP (38.0 years) (p = 0.003). Half of the patients were found to have IP during the initial diagnosis of SLE. The IP pattern on the HRCT images was consistent with that of usual interstitial pneumonia (UIP) in 25% of the patients and of nonspecific interstitial pneumonia (NSIP) in 55%. One patient exhibited acute exacerbation but survived. The radiological findings revealed that the disease progressed slowly in most of the patients; however, pulmonary function was retained. No significant differences were observed in the survival rates between patients with and without IP.

In SLE cases, IP primarily occurred in male and elderly patients. In addition to the NSIP pattern, the UIP pattern was evident on HRCT scans of IP-related SLE. The survival of SLE patients was unrelated to IP.