CCP antibody and Interstitial Lung Disease in Rheumatoid Arthritis
In general, rates of interstitial lung disease are high in rheumatoid arthritis. Case series have reported that 30 to 50% of patients with rheumatoid arthritis develop interstitial lung disease. Autopsy studies have shown a prevalence of nearly 80%, although many cases may have represented subclinical disease.
Patients who test positive for anti-cyclic citrullinated peptide antibody (anti-CCP) have the highest risk for developing interstitial lung disease. The level of anti-CCP antibody in the serum correlates with the severity of disease. Patients with levels greater than 125 units are more likely to have pulmonary fibrosis with honeycomb changes.
The reason for this correlation of anti-CCP antibody with interstitial lung disease is probably related to environmental exposures or smoking history. Inhalation of smoke and diesel fumes increase the activity of peptidylarginase, which is an enzyme in the lungs. Peptidylarginase cleaves arginine in proteins, converting it into citrulline, which is a foreign amino acid in humans. Consequently, patients develop anti-CCP antibodies against these citrullinated pulmonary proteins. Approximately 20% of patients with rheumatoid interstitial lung disease have detectable anti-CCP antibodies in bronchoalveolar lavage fluid approximately one year before they are detectable in serum.
Patients who continue to have active rheumatoid arthritis are much more likely to develop interstitial lung disease within 10 years after their initial diagnosis. Current dogma supports aggressive and complete control of arthritis manifestations in order to minimize the risk of progression of the interstitial lung disease.
Reference
Correia CS et al. Elevated anti-cyclic citrullinated peptide antibody titer is associated with increased risk for interstitial lung disease. Clin Rheumatol. 2019;38(4):1201-1206.
