This study aimed to investigate the characteristics of COVID-19-associated multisystem inflammatory syndrome in children (MIS-C) and Kawasaki disease shock syndrome (KDSS) and to compare the similarities and differences between the two diseases. The incidence of KDSS and MIS-C was also estimated. Medical records of patients diagnosed with MIS-C or KDSS at four hospitals from January 2013 to December 2022 were retrospectively reviewed. Thirty-one patients were enrolled in the study in either an MIS-C group (n = 22) or a KDSS group (n = 9). The incidence of KDSS in KD was 0.8% (9/1095) and the incidence of MIS-C versus KD was 10.2% (22/216). Compared with the MIS-C group, the KDSS group had longer hospital stays and more severe systemic inflammation (e.g., anemia, elevated C-reactive protein, hypoalbuminemia, and pyuria) and organ dysfunction (e.g., number of involved organs, shock, vasoactive infusion, and intensive care unit admission). All patients in the MIS-C group, but none in the KDSS group, including two patients during the COVID-19 pandemic, had laboratory evidence of SARS-CoV-2 infection. MIS-C and KDSS shared demographic, clinical, and laboratory characteristics; organ dysfunction; treatment; and outcomes. Overall severity was more severe in patients with KDSS than in those with MIS-C. The most important difference between MIS-C and KDSS was whether SARS-CoV-2 was identified as an infectious trigger.

Kim BJ, et al. J Korean Med Sci. 2022 May;37(20):e141. https://doi.org/10.3346/jkms.2022.37.e141

Songmi Lee, M.D., Danbi Kim, M.D., Beom Joon Kim, M.D., Ph.D., Jung Woo Rhim, M.D., Ph.D., Soo-Young Lee, M.D. Ph.D., Dae Chul Jeong, M.D., Ph.D.. J Rheum Dis 2023;30:272-7. https://doi.org/10.4078/jrd.2023.0022

Choi YH, et al. J Korean Med Sci. 2024 Jan;39(3):e33. https://doi.org/10.3346/jkms.2024.39.e33

As a major organ dysfunction, some patients with Kawasaki disease (KD) present with hypotension or shock, known as KD shock syndrome (KDSS). Organ dysfunction is also seen in macrophage activation syndrome (MAS), complicating KD (MAS-KD). Both KDSS and MAS are rare but potentially life-threatening complications of KD that require early recognition. In practice, however, KDSS and MAS can sometimes be overlooked in patients with KD. Here, we describe a 13-year-old boy who presented with prolonged fever, rash, and red eyes, and subsequently developed hypotension. He was diagnosed with KDSS and received inotropic agents and intravenous immunoglobulin (IVIG) treatment. However, his clinical and laboratory features deteriorated, and he met the diagnostic criteria for MAS. KDSS and MAS-KD share many overlapping features in terms of organ dysfunction. A diagnosis of KDSS is made when a patient with KD shows cardiac dysfunction, such as shock. If a KD patient displays multi-organ dysfunction, such as hematologic, hepatic, renal, or neurologic symptoms, they should be diagnosed with MAS-KD. As demonstrated in this case report, some KD patients may present with both cardiac and multi-organ dysfunction and require prompt and proper treatment for both.