Table 2. Comparison of characteristics between SJIA and KD

Variables	SJIA	KD
Demographic/etiology
Age	1–5 years & 10–14 years	< 5 years (mean 2.4)
Sex	M ≒ F (other JIAs, M < F)	M > F
Race/ethnicity	No differences	East Asia
Infectious triggers	NA, possible?	Important, but unknown
Distinct cytokines	IL-181)	IL-6
Clinical
Fever	Quotidian, spike ≥ 2 weeks	Persistent ≥ 5 days
Rash	Evanescent erythematous	Polymorphous
Arthritis	Symmetric (~80%)	Transient (~⅓)
Organ dysfunction1)	Possible	Possible (e.g., KDSS)
Laboratory
Neutrophilia	Common	Common
Thrombocytosis	Common	Common
CRP elevation	Common	Common
Anemia1)	Possible2)	Possible2)
Abnormal AST/ALT/albumin1)	Possible2)	Possible2)
Hyperferritinemia1)	Possible2)	Possible2)
D-dimer elevation1)	Possible2)	Possible2)
NT-proBNP elevation	Uncommon	Common
Treatment/outcomes
1st line	DMARDs, steroids	IVIG + aspirin
2nd line	Anakinra, tocilizumab	Steroids, infliximab
Cardiac complications	CAAs (possible), transient?Pericarditis (~40%)	CAAs (~25%), long-term sequelsPericarditis (common on ECHO)
Disease course	Polyphasic, chronic, recurrent	Monophasic, acute, self-limiting
Mortality	0.6% (6/962) [43,44]	0.02% (2/14,916) [23,42]

Principal features of MAS and can be seen in SJIA/MAS and KD/MAS.
Laboratory findings for severe or atypical forms of SJIA and KD (e.g., active SJIA, refractory KD, or incomplete KD).
SJIA: systemic juvenile idiopathic arthritis; KD: Kawasaki disease; M: male; F: female; NA: not available; IL: interleukin; KDSS: Kawasaki disease shock syndrome; CRP: C-reactive protein; AST: aspartate aminotransferase; ALT: alanine aminotransferase; NT-proBNP: N-terminal pro-brain natriuretic peptide; DMARDs: disease-modifying antirheumatic drugs; IVIG: intravenous immunoglobulin; CAAs: coronary artery abnormalities; ECHO: echocardiogram; SJIA/MAS: SJIA complicated with macrophage activation syndrome; KD/MAS: KD complicated with MAS.