Clinical significance of anti-filaggrin antibody recognizing uncitrullinated filaggrin in rheumatoid arthritis.

Filaggrin is expressed in the cornified layer of epidermis and known to be one of the antigenic targets in rheumatoid arthritis. Although the citrulline residue in filaggrin is thought to be an antigenic determinant recognized by autoantibodies, the diagnostic sensitivity of synthetic citrullinated peptide is variable. To investigate the implication of anti-filaggrin antibodies recognizing uncitrullinated filaggrin in rheumatoid arthritis, we assayed antibody titers using unmodified recombinant filaggrin in the sera from 73 patients with rheumatoid arthritis, 150 patients with other connective tissue diseases and 70 normal controls. We also performed the correlation analysis between antibody titers and the clinical variables in patients with rheumatoid arthritis. Titers of IgG anti-filaggrin antibodies were significantly higher in rheumatoid arthritis patients compared to normal controls (P=0.02), but not in patients with osteoarthritis, ankylosing spondylitis or systemic lupus erythematosus. IgG anti-filaggrin antibodies were more frequently found in patients with rheumatoid arthritis compared to normal controls (12.3% vs 1.4% respectively, P=0.04). An anti-filaggrin antibody titer was correlated with visual analogue scale of pain, tender joint count, Ritchie articular index or C-reactive protein, but not with anti-nuclear antibody or rheumatoid factor. These results suggest that anti-filaggrin antibody recognizes the uncitrullinated filaggrin as an antigen and its titer correlates with clinical parameters, explaining the variable sensitivity of anti-filaggrin antibody test.

Juvenile onset ankylosing spondylitis (JAS) has less severe spinal disease course than adult onset ankylosing spondylitis (AAS): clinical comparison between JAS and AAS in Korea.

OBJECTIVE: To assess the frequency of juvenile onset ankylosing spondylitis (JAS) in Korean patients with AS and to differentiate the clinical characteristics of JAS from adult onset ankylosing spondylitis (AAS). METHODS: We studied 98 consecutive patients with AS who visited the rheumatology clinic of a tertiary referral center and compared clinical and radiographic features of JAS (n = 41) with those of AAS (n = 57). RESULTS: Median age at onset in JAS was 14 years (range 7-16) and in AAS 22 years (range 17-38) (p < 0.01). Patients with JAS at presentation showed fewer spinal symptoms and more frequent peripheral joint symptoms than those with AAS (41.5% vs 80.7% and 73.2% vs 36.8%, respectively; p < 0.01). Current cervical spine disease was more frequent in AAS (66.7% vs 43.9%; p = 0.02) and current knee disease in JAS (26.8% vs 8.8%; p = 0.02). Patients with JAS showed a shorter tragus-wall distance (mean +/- SD 10.6 +/- 1.7 vs 13.1 +/- 6.9 cm; p < 0.01), more mobility on the modified Schober test (5.7 +/- 2.0 vs 4.0 +/- 2.6 cm; p < 0.01) and chest expansion (4.4 +/- 1.7 vs 3.2 +/- 1.8 cm; p < 0.01), and a better forced vital capacity (75.1 +/- 14.1% vs 82.1 +/- 16.1% of predicted value; p = 0.03) than those with AAS. Totally ankylosed sacroiliitis and spinal syndesmophyte on radiographs were less frequent in JAS patients than in AAS (19.5% vs 47.4% and 17.1% vs 54.4%, respectively; p < 0.01). CONCLUSION: The frequency of JAS (41.3%) among Koreans was higher than that reported for Caucasians. General joint involvement pattern at disease onset in JAS was similar to previous reports. Our data suggest that clinically and radiographically JAS has a less severe spinal disease course than AAS.