Lack of anti-citrullinated fibrinogen and anti-CCP antibodies in adult patients with Down syndrome

摘要

In a previous study by Nisihara et al. [1], ACPA measured by an ELISA for anti-CCP detection (INOVA Diagnostics, San Diego, CA, USA) and the IgM-rheumatoid factor (RF) measured by tur-bidimetry, were frequently found in the sera of young patients with Down's syndrome (up to 50% of the cases): 42 out of a first set of 150 patients were positive for IgM-RF (cut-off values of 40 UI/mL) versus 7/105 control children. Similarly, in a second set of 86 other sera, whilst 42 were positive for IgM-RF, 45 were also positive for anti-CCP, among which 16 weekly positive, and 29 moderately positive (above 40 units) [ 1 ], 25/86 (29%) being positive for both RF and anti-CCP [1]. None of these children (median of 4 years), was suffering from rheumatoid arthritis (RA), or juvenile arthritis [1 ]. Periodonti-tis, which favors the occurrence of anti-CCP [2], was not mentioned, and no precisions were given on other risk factors for citrullina-tion (HLA DR4, tobacco, and so on...). As a positivity for both FR and anti-CCP antibodies is highly specific for RA [3], we wished to replicate this puzzling observation. Indeed, there is an association of Down's syndrome with autoimmune diseases (thyroiditis, vitiligo, type I diabete mellitus, celiac disease) [4], and alterations of thymic medulla have been described in Down's syndrome, which could also deserve interest in RA [5].