Purpose: using the example of our own clinical case to demonstrate the complexity of diagnostics at the outpatient stage of multiple myeloma, occurring against the background of comorbid pathologies and the new coronavirus disease 2019 associated with pneumonia. Materials and methods. Based on the data from the medical record of an outpatient patient, a diagnostic search in a 70-year-old patient with pain in the thoracic spine was analyzed. Results. The article describes a case of multiple myeloma proceeding under the guise of thoracalgia against the background of concomitant cardiovascular diseases, as well as comorbid pathologies. During the examination, computed tomography of the chest organs for the addition of infectious complications in the form of pneumonia (COVID-19) showed characteristic bone changes in multiple myeloma. In all bones of the chest at the level of the thoracic spine, multiple solid formations with irregular contours were found, causing destruction of bone tissue. Biochemical examination revealed anemia, hypercalcemia, hypercreatininemia. In the patient, the M-gradient (Bens-Jones protein) in the urine is represented by kappa light chains in the monoclonal component and free kappa light chains. According to the results of the study, the clinical diagnosis was established: multiple myeloma stage III B, first diagnosed, with lesions of the ribs and thoracic spine. Conclusion. Diagnosis of multiple myeloma is a difficult task for a practicing therapist due to the lack of alertness and heterogeneity of the clinical picture. In elderly people, the diagnosis of multiple myeloma is much more difficult due to the presence of a significant number of comorbid pathologies.