Dermatomyositis (Wagner’s disease) is a rare autoimmune disease characterized by polymorphic skin eruptions and the progressive weakness of the proximal muscle groups. Dermatomyositis refers to idiopathic inflammatory myopathies, a broad group of autoimmune diseases affecting both children and adults. The incidence of dermatomyositis is 1.8 cases per 100.000 population. It is worth noting the possible association of this disease with oncological conditions and some systemic connective tissue disorders. Although the disease has long been known to the medical community, the disease etiology is unclear, and the pathogenesis mechanisms are still being studied. An important feature of dermatomyositis is the variety of clinical manifestations. The clinical presentation includes muscle, skin, and general symptoms, but the severity of each symptom group varies. Cutaneous symptoms in dermatomyositis are highly varied and non-specific. In addition, it is important to consider that skin lesions may precede muscle symptoms. The listed features of dermatomyositis clinical presentation may lead to diagnostic errors and inadequate therapy. Laboratory and instrumental studies play a crucial role in the diagnosis of dermatomyositis. Muscle tissue biopsy is necessary as it contributes to the timely diagnosis of the disease. The article addresses clinical presentation and diagnosis of dermatomyositis and describes clinical cases with significant differences in the clinical presentation. Also, the causes of diagnostic errors are analyzed. The article is of interest to rheumatologists, dermatovenerologists, and primary care physicians.