Multisystem Inflammatory Syndrome in Children vs Kawasaki Disease vs Macrophage Activating Syndrome Due to Systemic JIA

Children diagnosed with multisystem inflammatory syndrome (MIS-C) display some similarities and differences in clinical and laboratory features compared with those with Kawasaki disease (KD) and those with macrophage activating syndrome due to systemic juvenile idiopathic arthritis (sJIA-MAS), according to study results published in Rheumatology International.

Patients diagnosed with MIS-C, KD, or sJIA-MAS from 12 centers across Turkey and who were followed up for at least 6 months were included in the current analysis, and their demographic, clinical, and laboratory findings were compared.

Overall, 154 patients with MIS-C participated in the study, with a median age of 8.2 years. A total of 59 and 31 patients diagnosed with KD and sJIA-MAS were also included, with median ages of 3 years and 12 years, respectively.

Compared with KD and sJIA-MAS, MIS-C was more likely to include myalgia (39.6%), cardiac (50.6%), gastrointestinal (72.7%), and neurologic (22.1%) features.

Comparisons of laboratory findings between patients with MIS-C and with KD revealed lower levels of lymphocytes (950 vs 1700 cells/µL) and thrombocytes (173,000 vs 355,000 cells/µL) among patients MIS-C, along with higher pro-B-type natriuretic peptide (BNP) levels (1108 vs 55 pg/mL). Ferritin levels in patients with MIS-C, KD, and sJIA-MAS were 440, 170, and 10,442 ng/mL, respectively.

Compared with patients with sJIA-MAS, patients with MIS-C had shorter duration of hospitalization (P =.02), but more frequently required admission to intensive care (n=8 vs 55, respectively; P <.001).

A total of 28 of 154 patients with MIS-C met the MAS criteria and had a median MAS/sJIA (MS) score of -1.64 (-5.23 to 9.68) compared with a median MS score of -2.81 (-3.79 to -1.27) for those with sJIA-MAS.

Study limitations included different SARS-CoV-2 antibody testing methods across centers and limited data collection for certain parameters.

According to the researchers, “The improvement of the knowledge about this new disease and differentiation of it from already known mimickers may guide the clinicians to make timely and accurate diagnosis.”

Reference

Yener GO, Kisaarslan AP, Ulu K, et al. Differences and similarities of multisystem inflammatory syndrome in children, Kawasaki disease and macrophage activating syndrome due to systemic juvenile idiopathic arthritis: a comparative study. Rheumatol Int. Published online September 7, 2021. doi:10.1007/s00296-021-04980-7