Background/Purpose: Relapsing polychondritis (RP) is a highly heterogenous systemic inflammatory disorder that affects many organ systems, in particular, cartilaginous structures. Clinical presentations in RP are variable, making recognition and diagnosis of the disease challenging. Testing for anti-collagen II (CII) antibodies is sometimes used to confirm the diagnosis of RP; however, the data remains inconclusive as to what percentage of RP patients have anti-CII antibodies in their serum. Our objectives were to evaluate the utility of anti-CII antibody as a diagnostic tool and as a possible objective measure of disease activity in a large cohort of patients with RP.

Methods: Patients 18 years and older were recruited into a prospective observational cohort of RP. All patients met McAdams or Damiani’s diagnostic criteria for RP.  Anti-Cll antibodies were assayed via a clinically certified ELISA test (Mayo Clinic, Rochester, MN) in all patients evaluated from July 2019 to March 2020. Clinical features were compared between patients with RP stratified by presence of anti-CII antibody results using Fisher’s exact test or Wilcoxon rank sum test as appropriate. Linear regression was used to determine if antibody titer correlated to Physician Global Assessment (PGA) score of disease activity. Clinical ELISA test results were compared to results using a different ELISA test platform (cat. no. 2065, Chondrex Inc., Redmond, WA, USA).

Results: Forty-six patients were tested, and six patients (13%) had elevated levels of anti-CII antibodies. Of four patients (8%) who had repeat testing, anti-CII antibodies were persistently negative in 3 patients and discordant positive/negative in 1 patient.  Patients with elevated anti-CII antibodies compared to those without elevated antibodies were female (100 vs 63%, p = 0.02) with a significantly higher prevalence of oral ulcers (50 vs 15%, p = 0.04), genital ulcers (33 vs 5%, p = 0.02), costochondritis (66 vs 25%, p = 0.048), and Sicca symptoms (83 vs 33%, p = 0.03) and with a significantly lower prevalence of eye inflammation (0 vs 40%, p = 0.018), as well as lower absolute monocyte (median 0.33 vs 0.51 K/uL, p = 0.02) and white blood cell counts (median 4.54 vs 6.95 K/ul, p = 0.049).  There was no correlation between antibody titer and PGA (r= 0.18; p = 0.33). A total of 24 patients were tested on both ELISA platforms. Twenty-three patients tested negative on both platforms, but 1 patient that tested positive by the Mayo Clinic ELISA tested negative by the Chondrex ELISA. Thus, there was little concordance between platforms.

Conclusion: Anti-CII antibodies likely have a limited role as a diagnostic test or biomarker of disease activity in RP.  Few patients with RP have detectable anti-CII antibodies, and detection of these antibodies is dependent on testing platform. Presence of anti-CII antibodies may be associated with specific clinical symptoms and may be enriched in a subset of patients with RP who have mucocutaneous disease.  This subset is commonly referred to as MAGIC syndrome (mouth and genital ulcers with inflamed cartilage).  Whether anti-CII antibodies provide pathogenic insight for a smaller subset of patients with RP remains to be determined.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/anti-collagen-ii-antibodies-in-patients-with-relapsing-polychondritis/