Clinical Features and Outcome of Acute Exacerbation of Interstitial Pneumonia: Collagen Vascular Diseases-Related versus Idiopathic

<i>Background:</i> Relatively little is known about acute exacerbation (AE) of interstitial pneumonia associated with collagen vascular diseases (CVD-IPs). <i>Objectives:</i> This study was aimed at clarifying clinical characteristics and outcome in AE of CVD-IPs, compared with those of idiopathic interstitial pneumonias (IIPs). <i>Methods:</i> We retrospectively reviewed 112 admission cases with suspected AE of CVD-IPs or IIPs during 2003–2009. IIPs were diagnosed with idiopathic pulmonary fibrosis (IPF) or non-IPF, mostly based on radiologic findings. Of these, 15 AEs of CVD-IPs (6 rheumatoid arthritis, 6 dermatomyositis and 3 systemic sclerosis) and 47 AEs of IIPs (13 IPF and 34 non-IPF) were included. <i>Results:</i> The clinical characteristics in AE of CVD-IPs were similar to those of IIPs, except for younger age (63.3 ± 6.8 vs. 73.8 ± 9.1 years; p = 0.0001) and higher PaO₂/FiO₂ at the onset of AE (205 ± 81.2 vs. 145 ± 53.8 mm Hg; p = 0.002) in the former. Dermatomyositis-related interstitial pneumonia (IP) showed a relatively indolent onset and was often associated with worsening control of the underlying disease, whereas AE of other CVD-IPs resembled that of IIPs. 90-day mortality of 33% in AE of CVD-IPs was similar to that of IIPs (44%; p = 0.44) or non-IPF (34%; p = 0.94), but was significantly better than that of IPF (69%; p = 0.04). <i>Conclusion:</i> Clinical features and outcome in AE of CVD-IPs were similar, if not identical, to those of IIPs, having a significant impact on the clinical course. AE of advanced IPF with typical radiologic features seems to have higher mortality compared with other forms of IP.