Idiopathic pleuroparenchymal fibroelastosis (IPPFE) is a rare idiopathic interstitial pneumonia characterized by an upper lobe-dominant interstitial increase in predominantly elastic fibers. The accumulation of cases has resulted in a refinement of the disease concept, but there are no blood biomarkers to aid in the diagnosis or prediction of a progressive phenotype among PPFE patients. Several organizers, including latent transforming growth factor-β binding protein 4 (LTBP-4), are known to be involved in elastogenesis. However, the potential of LTBP-4 as a blood biomarker for PPFE has not been investigated.

We selected cases of clinically or histologically diagnosed IPPFE (n = 20) along with idiopathic pulmonary fibrosis (IPF) patients (n = 39) and healthy controls (n = 10). We quantified the protein levels of LTBP-4 in lung tissues and serum samples.

The LTBP-4 levels in lung tissue of PPFE patients were 2.16 times higher than those of IPF patients (p = 0.032). The serum concentration of LTBP-4 (pg/ml) in IPPFE was higher than that in healthy controls (1429 [154–3620] vs. 187 [56.4–490], p = 0.013). The serum concentration of LTBP-4 in IPPFE was markedly higher than that in IPF without a significant difference (1429 [154–3620] vs. 915 [491–1967], p = 0.671). In addition, a higher concentration of LTBP-4 was associated with a poor prognosis in IPPFE patients.

The serum concentration of LTBP-4 may aid in the diagnosis of IPPFE or the prediction of an aggressive phenotype.