Autoantibodies in patients with Down Syndrome: Early senescence of the immune system or precocious markers for immunological diseases?

Down syndrome (DS) patients present several immunological disturbances, with high rates of infections, malignancies and autoimmune phenomena. The present study aims to evaluate the prevalence of autoantibodies in children and adolescents with DS that are not usually investigated, and to establish possible clinical and laboratory associations. One hundred and fifty Caucasoid DS patients from southern Brazil (93M, 57F; median age 4 years) and 105 healthy children (58M, 47F; median age 8 years) were evaluated for the presence of anti-mitochondrial (AMA), smooth-muscle (SMA), liver-kidney microsomal (LKM), nuclear (ANA), gastric parietal cell (GPC) and neutrophil cytoplasmic (ANCA) antibodies, by indirect immunofluorescence, and rheumatoid factor (RF), by turbidimetry. Forty-three DS patients (28.6%) showed positivity to at least one autoantibody, in comparison with eight of the controls (7.6%; P < 0.001). RF was detected in 28% of the patients and 6.7% of the controls (P < 0.001). ANCA, SMA and ANA were positive in 0.66% of the patients, while AMA, GPC and LKM were negative in all the samples. Currently, none of the RF positive patients has clinical evidence of rheumatic disease. Data from the present study suggest that the high incidence of positive RF observed in DS patients might be related to the senescence of the immune system or could be an earlier marker of rheumatic diseases in these patients.