What tests are required when suffering from Gottron’s sign? The rash occurs on the extensor side of the metacarpophalangeal, phalangeal, and metatarsophalangeal joints, and can also be seen on the inner ankle joint. The rash is a purplish papule that may fuse into a plaque with fine scales on the surface, with central depression atrophy and hypopigmentation over time, and also often with capillary dilation. Electromyography: is the insertion of a needle electrode into skeletal muscle to record, amplify, and display the electrical activity of the muscle fibers extracellularly by means of an oscilloscope. Typical changes include triadic signs: (1) enhanced insertion potential activity, fibrillation potentials and positive sharp waves; (2) spontaneous odd high frequency discharges; and (3) low amplitude, short time frame, multi-phase motor unit potentials. Anti-ENA antibodies: Anti-ENA antibodies are called antibodies to saline-extractable nuclear antigens. They are autoantibodies against small molecule nuclear ribonucleoproteins (snRNPs) and small molecule cytoplasmic ribonucleoproteins (scRNPs), which do not contain histones. There are seven main anti-Sm antibodies , anti-SS-A/Ro antibodies, anti-SS-B/La antibodies, anti-Scl-70 antibodies, anti-Jo-1 antibodies, anti-U1-RNP antibodies, and anti-r-RNP antibodies. It is important for the diagnosis and differential diagnosis of connective tissue diseases and does not correlate significantly with disease severity and activity. determination of T lymphocyte subsets is an important indicator of the body’s cellular immune function and is important for the auxiliary diagnosis of certain diseases (such as autoimmune diseases, immunodeficiency diseases, malignancies, hematological diseases, allergic diseases, etc.), analysis of pathogenesis, observation of efficacy and monitoring of prognosis. Anti-PM-l antibody: Anti-PM-l antibody (Anti-PM-1 antibody) is a meaningful indicator for the diagnosis of myositis and the observation of its efficacy. Anti-PM-l antibody should be tested by fasting and drawing blood on an empty stomach after 8 pm the day before the test. The test result should be negative under normal conditions, but if there is a positive reaction, the patient may have a disease such as myositis. Extractable nuclear antigen (ENA) autoantibody spectrum band analysis: ENA is a non-histone acidic nuclear protein particle composed of many small molecules of RNA and peptides in cells. ENA mainly includes Sm, RNP, SSA, SSB, Jo-1, Scb-70 and other antigens. Different autoimmune diseases can produce different anti-ENA antibodies. the detection of ENA antibodies is important for the diagnosis and differential diagnosis of autoimmune diseases.