Anti-keratin and anti-cyclic citrullinated peptide autoantibodies in patients with juvenile idiopathic arthritis

Objective

We discuss the presence of anti-keratin antibodies (AKA) and anti-cyclic citrullinated peptide (anti-CCP) antibodies of the IgG class in sera of patients with defined juvenile idiopathic arthritis (JIA) of various subgroups with more than one year duration of the disease.

Methods

An indirect immunofluorescence test on rat oesophagus substrate (ImmuGloTM, Immco Diagnostics, Buffalo, USA) and enzyme-linked immunosorbent assay (Immunoscan RA, Eurodiagnostica, The Netherlands) were used for the detection and quantification of AKA and anti-CCP antibodies in 140 patients with JIA (64 male and 76 female) aged 2–47 years (median 16.5 years).

Results

Overall, AKA were found in 40/140 patients (28.6%, P = 0.04) including 2/11 systemic arthritis (18.2%), 2/32 oligoarthritis (6.3%), 18/52 RF negative polyarthritis (34.6%, P = 0.01), 14/18 RF positive polyarthritis (77.8%, P = 0.000002), 2/15 enthesitis related arthritis (13.3%) and 2/3 psoriatic arthritis patients. AKA were not found in a very small cohort of patients with extended oligoarthritis (n = 4) and unclassifiable arthritis (n = 5). Only 7/122 (5.7%) patients were positive for anti-CCP. The correlation between AKA and anti-CCP was 77.1% (P = 0.05).

Conclusion

We conclude that while AKA antibodies measured using IIF on rat oesophagus can be detected in patients with definite JIA with more than 1 year duration of the disease, only rare occurrence of anti-CCP was observed. We conclude that AKA occurred in any JIA patient category, however when statistically compared with healthy controls significantly higher frequencies were found only in a cohort of RF positive and RF negative polyarthritis.