The Difference in the Clinical Features of Acute Interstitial Pneumonitis and Severe Acute Respiratory Syndrome

Abstract

Purpose: In the early stages, the clinical and chest radiographic findings of acute interstitial pneumonitis (AIP) are often similar to those of severe acute respiratory syndrome (SARS). However, patients with AIP have a poor prognosis, while those with SARS can achieve a fair outcome. The objective of this study was to identify the differences in the early clinical features of these 2 diseases. Methods: The AIP group in our study included 5 patients with AIP who were histologically diagnosed at our hospital, and patients selected from a review of previously reported AIP cases. The SARS group included 76 patients with SARS who were treated at our hospital. The clinical symptoms, illness duration, laboratory data, and initial chest radiographic findings for each disease were evaluated. Results: A total of 69 patients with AIP were included in this study. The mean illness duration was significantly longer in the AIP group (16.3±18.3 days) than in the SARS group (3.4±2.5 days) (p＜0.001), and fever, myalgia, and diarrhea were significantly more prevalent in the SARS group (100%, 48.7% and 31.6%, respectively) than in the AIP group (50%, 1.6% and 0%, respectively) (p＜0.001). The white blood cell count was significantly higher among the AIP patients (15440±7835/mm^3) than the SARS patients (6000±2900/mm^3) (p＜0.001). No lesions were noted, and the involvement of 1 lobe in the initial chest radiographic presentation was significantly more prevalent among the SARS patients (26.3% and 43.4%) than the AIP patients (0% and 0%)(p＜0.001). The intubation rate and mortality rate were significantly higher in the AIP group (92.5% and 47.8%) than the SARS group (30.3% and 19.7%)(p＜0.001). Conclusion: For a differential diagnosis of AIP and SARS, special attention should be given to the following clinical findings: shorter illness duration, fever, myalgia, diarrhea, and a normal leukocyte count. Initial chest radiographic findings with no lesions, or the involvement of 1 lobe, were more common among the SARS patients than the AIP patients.