["When it rains, it pours" - de novo diagnosed multiple myeloma with invasive Streptococcus pneumoniae infection in severe COVID-19 complicated with cytokine storm].

With the appearance of SARS-CoV-2, the range of infections, considered the most common cause of death for people with multiple myeloma, has expanded. Although the omicron variant (PANGO B.1.1.529) of SARS-CoV-2, that dominates the world at the time of manuscript writing, is less likely to cause fatal infection in immunocompetent patients compared to the delta variant (PANGO B.1.617.2), its transmissibility did not decrease. The likelihood of a severe or critical course of COVID-19 in patients with multiple myeloma is increased by the humoral and cellular immunosuppression caused by the malignancy itself, its targeted hematological treatment, and other comorbidities associated with the disease (e.g., chronic kidney failure). Antiviral therapies, monoclonal antibody preparations used as pre- or post-exposure prophylaxis, and possibly convalescent plasma therapy, started as early as possible might prevent the clinical progression of COVID-19. While the incidence of community-acquired co-infections accompanying COVID-19 in the average population is not exceptionally high, in people with multiple myeloma, Streptococcus pneumoniae infection that follows respiratory viral diseases is approximately 150 times more likely to cause invasive disease. As a result of modern oncohematological treatment, multiple myeloma has now become a chronic disease accompanied by relapses, and those affected should be immunized against the above two pathogens. In our manuscript, we describe the case of an adult patient with severe COVID-19 complicated by cytokine storm and invasive Streptococcus pneumoniae infection who was diagnosed with de novo multiple myeloma during hospital care, and, finally, we briefly review the related literature data. Orv Hetil. 2023; 164(20): 763-769.