Dermatomyositis Gottron’s sign: This sign is present in about 70% of cases of dermatomyositis. It presents as a reddish-purple maculopapular rash on the skin over the metacarpophalangeal and proximal phalangeal joints with a flattened apex and a little desquamation, which becomes atrophic and hypopigmented over time. Stiff capillary dilatation and petechiae are seen in the nail root folds, which aid in the diagnosis. This sign was first depicted by Gottron in 1930 and is considered a specific rash for DM. Flattened purplish-red papules with furfuraceous scales on the extensor aspect of the phalanges, metacarpophalangeal joints, well defined, are seen in 30% of patients, and the lesions subside leaving atrophy, hypopigmentation, and capillary dilatation. Differential diagnosis of dermatomyositis Gottron’s sign: dermatomyositis (DM), also known as cutaneous heterochromatic dermatomyositis (poikilodermatomyositis), is an autoimmune connective tissue disease, mainly affecting the transverse striated muscle, presenting a non-suppurative inflammatory lesion mainly infiltrated by lymphocytes, which may be accompanied by or not accompanied by a variety of skin lesions, and may be accompanied by a variety of internal organs. It may or may not be accompanied by various skin lesions, and may also be accompanied by various visceral lesions. Polymyositis (PM) refers to this group of diseases without skin damage, the exact etiology is not clear enough, it may be viral infection, the body’s immune abnormality of abnormal self-recognition and vascular lesions, which may also be interrelated, for example, lentiviral infection of rhabdomyosin fibers can lead to changes in antigenicity of the myofibers, which are mistaken for “foreigners” by the immune system, thus leading to the formation of a “foreigner”, which may lead to the development of a “foreigner”. For example, lentiviral infection of the transverse muscle fibers can lead to antigenic changes in the muscle fibers, which are mistaken by the immune system as “foreign”, resulting in vasculitis and the development of the disease. The rash occurs on the extensor aspects of the metacarpophalangeal, phalangeal, and metatarsophalangeal joints, and can also be seen on the medial ankle joints. The rash is a purplish-red papule, which may fuse to form a plaque, with a finely scaled surface, and a central depression of atrophy and hypopigmentation over time, as well as often with capillary dilatation. According to the patient’s symmetrical proximal muscle weakness, pain and tenderness, accompanied by characteristic skin lesions such as periorbital-centered purplish-red edematous plaques, Gottron’s sign, and nail root fold stiffness and dilated capillary erythema, the diagnosis is generally not difficult to make, combined with the serum muscle plasma enzymes and CPK, LDH, AST, ALT, and aldolase elevation, and, if necessary, combined with the changes in electromyography and the biopsy of the diseased muscle, the diagnosis can be confirmed. examination, the diagnosis of dermatomyositis can be confirmed.