Platythorax progresses with lung involvement in pleuroparenchymal fibroelastosis

Background: Patients diagnosed with pleuroparenchymal fibroelastosis (PPFE) exhibit unique clinical features, including upper lobe-dominant lung involvement and platythorax (or flattened thoracic cage). Although platythorax have been shown to be a sign of disease progression, the temporal relationship between the progression of platythorax and the extent of lung involvement has not been closely investigated.

Methods: We retrospectively investigated patients diagnosed with PPFE, who did not exhibit fibrotic lesions other than PPFE in the lower lobes. We estimated the fibrosis score, which is a visual score indicating the percentage of lung parenchyma occupied by the disease on computed tomography images selected every 2 cm from the lung apex to the lung base, and the flat chest index (the ratio of the anteroposterior diameter of the thoracic cage to the transverse diameter of the thoracic cage). Additionally, we investigated serial changes in the flat chest index and fibrosis score.

Results: A total of 29 patients were included in this study. The fibrosis score was found to be weakly and inversely correlated with forced vital capacity %predicted at the diagnosis (r = -0.40, p = 0.038). Furthermore, the annual changes in the flat chest index and fibrosis score was found to be moderately and inversely correlated (r = -0.663, p = 0.0037).

Conclusions: These results indicate that there is a causal relationship between the progression of fibroelastosis and that of platythorax in patients with PPFE.