Case Series Evaluating Lymphocyte Subgroups at Diagnosis and After Treatment in Multisystem Inflammatory Syndrome Associated with COVID-19 in Children

Objective: In this case series, we aimed to examine the changes in lymphocyte subgroups in children diagnosed with the multisystem inflammatory syndrome (MIS-C) during the acute phase and in the first month after treatment. Material and Methods: Ethics committee approval was received for the study from the Ethics Committee of Ondokuz Mayis University patient data were analyzed from medical records in an electronic database. Initial immunological evaluations of our first five patients diagnosed with MIS-C were made, steroid and IVIG treatments were given to the patients, and lymphocyte subgroups were evaluated for the second time in the first month for control purposes. Results: In MIS-C cases, it was observed that lymphopenia was severe in the acute period, CD3 T cells decreased, the ratio of 2:1 between cytotoxic T cells and helper T cells was impaired, B cells increased proportionally, and NK cells were normal or decreased. When we evaluated MIS-C cases with the control lymphocyte subgroup in the first month, it was observed that lymphopenia improved and CD3 T cells increased proportionally, and active T cells decreased to normal values in the first month after treatment. On the other hand, while naive B cells decreased, non-switching and switching B cells increased and NK cells decreased. Conclusion: While COVID-19 is an acute infection, MIS-C is associated with cytokine storm induced by the acute infection. Immunologic assessment of MIS-C cases is considered important since the condition causes immune dysregulation in the host immune system. Lymphopenia, increased B cell count, reversal of the CD4/CD8 ratio, and increased active T cell count may be beneficial in the early diagnosis of MIS-C. Since it is thought that the cytokine storm causes complications in MIS-C, immediate administration of IVIG treatment is considered essential. Although it was demonstrated that the disease manifests with marked cellular changes, there is still a need for further studies.