Dermatomyositis Gottron’s sign is characterized by a flat purplish papule on the extensor aspect of the digits and metacarpophalangeal joints with bran-like scales and well-defined borders. How to check Gottron’s sign of dermatomyositis: Routine laboratory tests: normal or lower white blood cell count, 2/3 may have increased blood sedimentation. Blood IgG, IgA, IgM, immune complexes, and a2 and Y globulins may be increased. Complement C3 and C4 may be reduced. Measurement of myoglobin: Myoglobin is present only in cardiac muscle and transverse muscle. Most patients with myositis have elevated serum myoglobin, and its fluctuations parallel the disease, sometimes its changes appear before CK changes, but the specificity is poor. Autoantibodies: Autoantibodies can be detected in the serum of most patients. These antibodies can be divided into: (1) myositis-specific autoantibodies (myositis-specificautoantibodies) that are only found in inflammatory myopathies; (2) autoantibodies that are often found in inflammatory myopathies but are not specific for myositis; and (3) autoantibodies that are found in syndromes in which myositis and other diseases overlap. autoantibodies. For example, anti-rRNP and anti-Sm antibodies can be detected in cases with SLE, anti-Scl-70 antibodies in cases with systemic sclerosis, and anti-SSA and anti-SSB antibodies in cases with dry syndrome. Non-specific antibodies such as anti-myoglobin antibodies, rheumatoid factor, anti-myosin antibodies, anti-troponin, and pro-myosin antibodies may also be detected. The blood picture usually has no significant changes, sometimes there is mild anemia and leukocytosis, about 1/3 cases have increased eosinophilia, moderate increase in erythrocyte sedimentation rate, unchanged or decreased total serum protein, decreased albumin ratio, decreased albumin, and increased α2 and γ globulin. Immunological testing: Two types of autoantibodies can be detected in the serum of DM/PM patients. 1, direct antibodies against muscle and its components as well as anti-nuclear and cytoplasmic antibodies. 2, other immunological tests about 1/3 of patients have mild to moderate reduction in C4 and occasional reduction in C3, and hereditary C2 defects in DM have been reported. In some cases, CIC is increased. Direct immunofluorescence assay of hair cell vessel walls in lesioned muscles especially in pediatric cases showed IgG, IgM and complement deposition, but focal Ig and C deposition was seen at the focal dermal epidermal junction of lesioned skin lesions. However, there was no continuous deposition, unlike SLE.