Acute exacerbation (AE) is currently established as a distinct condition with acute deterioration of respiratory status in idiopathic pulmonary fibrosis (IPF). Recently, several studies have reported that AE also occurred in interstitial pneumonias other than IPF, such as collagen vascular disease-associated interstitial pneumonia (CVD-IP). However, the incidence of AE in CVD-IP and its clinical characteristics remain to be fully determined. This study was conducted to elucidate cumulative incidence of AE in CVD-IP and its clinical features.

We reviewed 83 biopsy-proven CVD-IP patients, estimated cumulative incidence of AE, and examined its clinical characteristics.

Among 83 CVD-IP patients, six patients with a mean age of 65.7 years developed AE (overall incidence, 7.2%; 1-year incidence, 1.25%). Underlying CVDs included rheumatoid arthritis (RA) (n=5; overall incidence, 20.0%) and primary Sjögren syndrome (n=1; overall incidence, 5.9%). Patients with AE showed acute respiratory deterioration with severe hypoxemia (mean PaO₂/FiO₂ ratio, 131). Radiologically, ground-glass opacity was superimposed on the underlying reticular abnormalities. Preexisting histological patterns included three usual interstitial pneumonia (UIP) and two non-specific interstitial pneumonia (NSIP). Five (83.3%) of six patients died of respiratory failure despite intensive therapy. Univariate Cox's proportional hazards analysis showed that age and RA diagnosis were significantly associated with AE. Multivariate Cox's proportional hazards analysis indicated that age was an independent significant factor predicting AE.

These data suggest that AE can occur in CVD-IP, and this condition is closely similar to that of IPF with poor prognosis. AE is most common in RA, and associated with higher ages.