Elevated Serum Procollagen III Aminopeptide Levels in Sarcoidosis

Procollagen III aminopeptide (P-III-P), a peptide released during the conversion of type III procollagen to type III collagen, is considered a potential marker of fibroblast activity in a variety of pulmonary and extrapulmonary diseases. The aim of the present article was to investigate the levels of P-III-P in serum samples (sP-III-P) from a large number of sarcoid patients, in particular looking at its relationship with other markers of disease activity and its presumed role as a marker of pulmonary fibrosis. sP-III-P has been radioimmunoassayed in an overall series of 57 patients and the levels were higher (19.18±9.17 ng/ml) than in 25 age- and sex-matched controls (11.32±2.15 ng/ml; p 67 Ga uptake, bronchoalveolar lavage [BAL] lymphocyte percent, vital capacity, and lung diffusing capacity). The relationship with S-ACE was confirmed in a longitudinal follow-up study, where sP-III-P strictly paralleled the S-ACE behavior. Finally, the initial sP-III-P levels did not predict cases either with disease relapse or resistance to corticosteroid treatment. We conclude that, in our study, sP-III-P levels failed to characterize sarcoid patients with radiologic fibrotic pattern (stage III), and, in addition, were unable to predict which patients would have a poor prognosis. Rather, they reflect a metabolic activity of sarcoid granuloma cells. Thus, the usefulness of sP-III-P in the treatment of patients with sarcoid may be considered similar to that of S-ACE.