Systemic scleroderma is an autoimmune disease of the connective tissue of unknown etiology. It is characterized by skin induration, lesions in the musculoskeletal system and the internal organs, and the Raynaud syndrome. An important component in pathogenesis of systemic scleroderma is disturbance of microcirculation involving endothelial proliferation and destruction, wall thickening and narrowing of the microvessel lumen, vasospasm, hemocyte aggregation, stasis, deformation and reduction of the capillary network (obliterating microangiopathy). Two main forms of the disease are distinguished: the diffuse and localized ones. The systemic nature of the diffuse form of systemic scleroderma is most obvious in the skin, but the digestive tract, respiratory organs, kidneys and the cardiovascular, endocrine, musculoskeletal and genitourinary systems are also affected. The incidence rate of systemic scleroderma is 6.3—12 cases per million population. Single case reports on scleroderma combined with other autoimmune diseases, including type 1 diabetes mellitus, in children and adolescents are available in literature. A rare case of a combination of two autoimmune diseases, type 1 diabetes mellitus and systemic scleroderma, in a 13-year-old girl is reported in this paper.