Gottron’s sign is caused by dermatomyositis and is its clinical skin symptom. It presents as a reddish-purple maculopapular rash on the skin at the metacarpophalangeal and proximal phalangeal joints, flattened on the top surface with a little desquamation, with skin atrophy and hypopigmentation over time. Stiff capillary dilatation and petechiae are seen in the nail root crease, which helps in the diagnosis. What are the causes of dermatomyositis Gottron’s sign? Dermatomyositis 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 and atrophy and hypopigmentation over time, and also often with capillary dilation. The exact etiology of the disease is unknown and is generally believed to be related to genetics and viral infections. There are significant racial differences in the onset of polymyositis and dermatomyositis. The presence of this disease in identical twins and first-degree relatives also suggests a genetic predisposition. It usually starts insidiously and progresses slowly over weeks, months, and years. Very few patients have an acute onset, with severe muscle weakness, or even rhabdomyolysis, myoglobulinuria and renal failure within days. Patients may have morning stiffness, fatigue, loss of appetite, weight loss, fever (low to moderate fever or even high fever), joint pain, and in a few patients, Raynaud’s phenomenon. Muscle involvement is usually bilateral and symmetrical, with scapular and pelvic girdle muscles most commonly involved, followed by cervical and pharyngeal muscles, respiratory muscles are rarely involved, and orbicularis oculi and facial muscles are rare. About half of the patients have myalgia and/or muscle pressure. Myasthenia gravis initially affects the scapular girdle and pelvic girdle muscles, while distal myasthenia gravis is rare. About half of the patients have involvement of the cervical muscles, especially the cervical flexors, which manifests as difficulty in raising the head when lying down and inability to tilt the head when sitting; involvement of the pharyngeal or upper transverse esophageal muscles may present with difficulty in swallowing, hoarseness, difficulty in pronunciation, and choking and coughing when ingesting liquid food through the nostrils. Involvement of the smooth muscle of the digestive tract is rare. Weakness of the lower esophageal sphincter can lead to acid reflux, esophagitis, and in chronic cases, esophageal stricture. When the scapular girdle is involved, there can be difficulty in raising the arm, and inability to comb the hair and dress; respiratory muscle weakness can cause chest tightness and difficulty in breathing, and in severe cases, a ventilator is needed to assist breathing; when the patient has pelvic girdle muscle weakness, it can manifest as difficulty in getting up and down steps, inability to stand on its own after squatting or difficulty in standing up from the seat, gait staggering, and difficulty in walking. Rheumatism: It is a group of diseases that mainly affect joints, bones, muscles, blood vessels and related soft tissues or connective tissues, most of which are autoimmune diseases. The onset of the disease is more insidious and slow, with a long course, and most of them have a genetic predisposition. Diagnosis and treatment are difficult; different autoantibodies can be detected in the blood, which may be related to different HLA subtypes; good short-term or long-term palliative response to non-steroidal anti-inflammatory drugs (NSAID), glucocorticoids and immunosuppressive drugs. Dermatomyositis without myositis: It is a new type of dermatomyositis with characteristic dermatomyositis skin changes without myositis that lasts for 24 months; it has the same high rate of concomitant malignancy as dermatomyositis and is a concomitant neoplastic connective tissue disease.