A Case of Dermatomyositis Coexisting with Both Anti-Mi-2 and Anti-NXP-2 Antibodies.

Myositis-specific autoantibodies (MSAs) including anti-Mi-2 and anti-nuclear matrix protein 2 (NXP-2) antibodies have been detected in the patients with dermatomyositis (DM), and are useful tools for identifying clinical subsets of DM. MSAs are exclusively found in DM patients. Anti-Mi-2 antibody-positive DM patients show the typical skin lesions and myositis and are rarely associated with internal malignancy and interstitial lung disease (ILD). On the other hand, adult DM patients with anti-NXP-2 antibody often show calcinosis and internal malignancy, but rarely ILD. In addition, anti-NXP-2 antibody-positive DM patients have severe phenotype with myalgia, peripheral edema, and significant dysphagia, but with mild skin lesions. Herein, we report a rare case of classic DM coexisting with both anti-Mi-2 and anti-NXP-2 antibodies, clinically, without ILD or internal malignancy. Our patient had typical skin manifestations, muscle weakness, muscle pain, and general fatigue without calcinosis, peripheral edema, or dysphagia. Thus, the clinical phenotype was similar to anti-Mi-2 antibody-positive DM.