Myositis specific antibodies: frequency in different populations

Myositis specific autoantibodies (MSA) are the most specific markers of idiopathic inflammatory myopathies (IIM). There is no evidence of presence MSA in patients with other neuromuscular or connective tissue diseases. We compared the frequency of MSA in two groups of IIM patients, one from Poland and one from North America and found no significant statistical differences (21% and 25% respectively). There was a significant difference between the occurrence of immunological marker PM-Sci in scleromyositis patients (22.85% in group I and 7.1% in group II). This figure was also greater than those previously reported in North Americans (2-10%) and Japanese (extremely seldom). These findings confirm the association between MSA and several homogenous clinical syndromes: antisynthetases with the antisynthetase syndrome, anti-SRP with severe, resistant to treatment myositis, anti-Mi-2 with classic, benign dermatomyositis. They underscore the importance of including MSA in the routine diagnostic workup of IIM.