Introduction:
To describe cases meeting the criteria of Kawasaki disease (KD), with particular consideration of the first 2 cases of paediatric inflammatory multisystem syndrome temporarily associated with SARS-CoV-2 infection (PIMS-TS) in patients in the Malopolska region in the first wave of the disease caused by SARS-CoV-2 infection (COVID-19) pandemic.

Material and methods:
From 4 March to 15 July 2020 a total of 11 children meeting KD criteria were hospitalised in the Department of Infectious Diseases and Paediatrics, S. Żeromski Specialist Hospital in Krakow and the Clinic of Children’s Diseases, Department of Paediatrics, Jagiellonian University Medical College in Krakow. This paper analyses the data collected and describes in detail the disease in 2 children with PIMS-TS.

Results:
None of the 11 children who met the criteria of KD had a positive SARS-CoV-2 PCR test on admission. SARS-CoV-2 IgG test results were positive in 2 patients. All children presented with fever, rash, and conjunctivitis; 9 with swollen hands and feet; 8 with mucous membrane changes; 5 with abdominal symptoms; 5 with respiratory symptoms; and 1 with neurological signs. As regards laboratory tests, C-reactive protein (CRP), procalcitonin, lymphocytes, platelets, All were assessed in all patients, albumin in 10/11, lactate dehydrogenase (LDH), fibrinogen in 9/11, troponin and ferritin in 6/11, pro-BNP, D-dimers in 8/11. Echocardiography was performed in all patients and showed coronary artery abnormalities in 4 children. In PIMS-TS significant elevation of procalcitonin, CRP, D-dimers, N-terminal prohormone of brain natriuretic peptide (NT-pro-BNP), and thrombocytopaenia were observed.

Conclusions:
1. Because of the asymptomatic course of SARS-CoV-2 infection in children who subsequently developed PIMS-TS and the absence of any viral genetic material in a sample collected from the upper airways upon PIMS-TS diagnosis, a detailed epidemiological interview and a reliable serology testing for SARS-CoV-2 infection are necessary in each case meeting KD or PIMS-TS criteria. 2. There is a need to look for new factors differentiating PIMS-TS and KD, other than polymerase chain reaction (PCR) and serology tests.