Kodera M et al. (2005) Serum pulmonary and activation-regulated chemokine/CCL18 levels in patients with systemic sclerosis. Arthritis Rheum 52: 2889–2896

Pulmonary fibrosis (PF) is a common complication of systemic sclerosis (SSc) and is a major cause of death. At present, KL-6 antigen and surfactant protein D (SP-D) are the most reliable serum markers for monitoring PF; however, they do not always accurately reflect underlying disease or improvements following immunosuppressive therapy.

Pulmonary and activation-regulated chemokine (PARC) levels are known to be raised in the lungs of patients with interstitial lung diseases. In this retrospective, longitudinal study of 21 SSc patients, PARC levels were found to correlate with PF and were a more sensitive reflection of PF activity than KL-6 and SP-D, levels. Increased PARC levels were associated with decreased diffusing capacity for carbon monoxide and decreased vital capacity. Serum PARC levels decreased more rapidly than KL-6 and SP-D levels in patients responding to immunosuppressive therapy. This probably reflects the fact that PARC is a product of activated alveolar macrophages and therefore parallels lung inflammation more closely than KL-6 and SP-D, which are released in response to alveolar damage and regeneration.

These results need to be confirmed in a larger group of patients, but based on these findings, serum PARC shows promise as a marker of PF in patients with SSc, although the authors caution that PARC levels should be interpreted alongside other clinical parameters and radiologic assessment to fully evaluate PF activity.