Distinct characteristics of multisystem inflammatory syndrome in children in Poland

Abstract

During the winter months of 2020/2021 a wave of multisystem inflammatory syndrome in children (MIS-C) emerged in Poland. We present the results of a nationwide register aiming to capture and characterise MIS-C with a focus on severity determinants. The first MIS-C wave in Poland was notably high, hence our analysis involved 274 children. The group was 62.8% boys, with a median age of 8.8 years. Besides one Asian, all were White. Overall, the disease course was not as severe as in previous reports, however. Pediatric intensive care treatment was required for merely 23 (8.4%) of children, who were older and exhibited a distinguished clinical picture at hospital admission. We have also identified sex-dependent differences; teenage boys more often had cardiac involvement (decreased ejection fraction in 25.9% vs. 14.7%) and fulfilled macrophage activation syndrome definition (31.0% vs. 15.2%). Among all boys, those hospitalized in pediatric intensive care unit were significantly older (median 11.2 vs. 9.1 years). Henceforth, while ethnicity and sex may affect MIS-C phenotype, management protocols might be not universally applicable, and should rather be adjusted to the specific population.

Figure 1

Geospatial and temporal distribution of analyzed cases. (a) Shows locations of analyzed cases and reporting sentinel sites. (b) Shows the counts MIS-C hospitalisations in respective days in the analyzed period, between 4th March 2020 and 20th February 2021. Bars indicate daily counts, while the black line presents the 7-day moving average.

Figure 2

Incidence of reported MIS-C cases within the Polish population of children aged 0–18 years, according to age and sex.

Figure 3

Incidence of the selected events within the study group, according to age and sex. KD/aKD, Kawasaki disease/atypical Kawasaki disease; MAS, macrophage activation syndrome. Musculo-osteoarticular symptoms encompassed: muscle pain, arthralgia, or arthritis. Lower respiratory symptoms encompassed: chest pain, cough, or dyspnea. Cardiac involvement encompassed left ventricular ejection fraction < 55%, or coronary artery abnormalities (dilation or aneurysm), or pericardial effusion.