Anti-centromere antibodies (ACA) are an immunological marker for diagnosis of CREST syndrome, a limited form of systemic sclerosis. At least 9 proteins are known to be associated with the centromere complex, but CENP-B is normally considered to be the major centromere antigen. CENP-B has a molecular weight of approximately 66 kDa and plays an important role in the formation of the centromeric chromatin. CENP-B antibodies are present in the sera of up to 80% of patients with CREST syndrome. These autoantibodies are also often detected in sera from patients with Raynaud's phenomenon and occasionally in other rheumatic diseases such as systemic lupus erythematosus, Sjögren’s syndrome, and rheumatoid arthritis. ACA have also been reported to occur with high prevalence in patients with primary biliary cirrhosis, in patients with malignancies and occasionally in normal individuals.