Kawasaki Disease (KD) and Multisystem Inflammatory Syndrome in Children (MIS-C) are two related conditions that primarily affect pediatric patients. The overlap in clinical symptoms, physical findings, and laboratory results between MIS-C and KD complicates diagnosis and treatment, as children with MIS-C may fulfill the criteria for KD. Early recognition of distinguishing clinical, laboratory, and echocardiographic findings is crucial for timely diagnosis and appropriate treatment, which can mitigate the risk of severe cardiovascular, gastrointestinal, and neurological complications.

This study aims to compare the clinical profile, laboratory profile, 2-D echocardiographic findings, treatment, and outcome ofchildren with KD vs MIS-C at a tertiary hospital in the Philippines.

A retrospective, analytic cohort study was done to differentiate the clinical profiles, laboratory profile, treatments, and outcomesof pediatric patients aged less than 19 years old, admitted with a diagnosis of KD, from January 2016 to December 2019 (pre-COVID-19 pandemic), and MIS-C cases admitted from January 2020 to December 2023, in a private, urban, tertiary hospital. Descriptive statistics (frequency and proportion, mean and standard deviation, median and inter-quartile range) were used to summarize the general and clinical characteristics of the participants. Independent T-test, Mann-Whitney U test and Fisher’s Exact/Chi-square test were used to determine the difference of mean, median and frequency of laboratory parameters among groups.

The study included 87 patients, with 60 categorized in the KD group (13 diagnosed with complete KD and 47 with incomplete KD) and 27 in the MIS-C group. MIS-C patients were more likely to be older (p = 0.023), present with GI symptoms such as vomiting (48.2% in MIS-C vs. 12.8% in KD) and abdominal pain (40.7% vs. 6.4%), respiratory symptoms such as shortness of breath (29.6% vs 0%) and wheezing (14.8% vs 0%), have lower WBC (6.30 in MIS-C vs. 13.07 in complete KD and 10.18 in incomplete KD, p < 0.001), ANC (5,940 in MIS-C vs. 13,660 in complete KD and 10,432 in incomplete KD, p = 0.002), and platelet count (280 in MIS-C vs. 368 incomplete KD and 364 in incomplete KD, p = 0.13), and experience more complications such as myocarditis (14.81% vs. 0%), hypotension (18.52% vs. 0%), shock (14.81% vs. 0%), and pneumonia (40.74% vs. 17.02% for incomplete KD and 7.69% for complete KD). In contrast, key features of KD, including conjunctival injection (100% in KD vs. 25.9% in MIS-C), rash (100% vs 59.3%), oral changes (92.3% vs. 22.2%), and cervical lymphadenopathy (92.3% vs. 29.6%), elevated laboratory results of CRP (12.89 in MIS-C vs. 46.53 incomplete KD and 111.15 in incomplete KD, p < 0.001), ESR (41.91 in MIS-C vs. 61.73 in complete KD and 82.49 in incomplete KD, p= 0.003), and AST/ALT ratios (0.42 in MIS-C vs. 1.88 in complete KD and 0.62 in incomplete KD, p = 0.034) were more frequently observed in KD patients. Combination therapy involving intravenous immunoglobulin (IVIG), methylprednisolone, and acetylsalicylic acid (ASA) was more common in MIS-C patients than in KD patients (48.15% in MIS-C vs. 7.69% for complete KD and 2.13% forincomplete KD), who mainly received IVIG and ASA alone (84.62% in complete KD and 93.62% in incomplete KD vs 3.7% in MIS-C).

This study highlights key clinical and laboratory differences between MIS-C and KD in a private tertiary hospital setting. MIS-C patients were generally older, exhibited more GI and respiratory symptoms, and had a higher risk of serious complications. In contrast, KD cases more often presented with classic mucocutaneous signs and elevated inflammatory markers. These findings underscore the importance of early differentiation, as MIS-C often requires more intensive management. The study also identifies practical diagnostic indicators including CBC parameters such as WBC, ANC, and platelet count that may aid clinicians, particularly in resource-limited settings. Further multicenter research involving both public and private hospitals is needed to validate and enhance the diagnostic criteria.