Difficult patient: overlap-syndrome, paraneoplastic syndrome or random polymorbidity?

Objective: to describe a clinical case of CRST syndrome in combination with an oncological disease. Materials and methods. Patient S., 64 years old, complained of dizziness, stiffness in the hands, numbness of fingers, loss of appetite. After a thorough questioning and examination, systemic scleroderma was suspected and an additional examination was prescribed, which included routine clinical and biochemical tests, a "thyroid panel", rheumatological parameters, tumor markers, chest x-ray, ultrasound of the abdominal cavity, thyroid ultrasound, electrocardiography, echo gastroscopy. Results: Based on the examination data, the diagnosis was made of adenocarcinoma of the antrum of the stomach, as well as limited scleroderma (CREST syndrome) in combination with chronic autoimmune thyroiditis (СAIT). The course of the disease almost completely fits into the CREST syndrome, but there was no confirmation of esophageal dysfunction or esophagitis (in this case, the term CRST syndrome is sometimes used). The rest of the limited version of scleroderma was beyond doubt. Cases when CAIT accompanied systemic lupus erythematosus, systemic scleroderma, Sjogren's syndrome, mixed connective tissue diseases, etc., have not only been described, but also studied for overlap conditions - overlap syndromes. Conclusion. The pathogenetic mechanisms of the association of various autoimmune diseases are not completely clear; it is assumed that the key role in the formation of polyautoimmunity is played by defects of the immune system associated with polymorphism of various genes, in combination with environmental factors and hormonal disorders. And the detection of an oncological process does not look random: because of autoimmunity, an aberrant immune response, or the use of immunomodulatory drugs, many of the rheumatic diseases seem to increase the risk of neoplasia Key words: gastric adenocarcinoma, CREST-syndrome, limited scleroderma, chronic autoimmune thyroiditis, overlap-syndrome, rare disease, etiology, diagnostic research, paraneoplastic syndrome, methodology of diagnosis.