Article in Japanese

An infantile case of suspected systemic juvenile idiopathic arthritis complicated by coronary arterial lesions mimicking Kawasaki disease

Miki MINAMI ^1,2）, Yuichiro IMAI ^1）, Hodaka KOBAYASHI ^1）, Hiroaki SUDO^1）,Tadafumi YOKOYAMA^3）, Taizo WADA^3）, Kazunari KANEKO^2）

Both Kawasaki disease (KD) and systemic juvenile idiopathic arthritis (sJIA) are inflammatory diseases with unknown causes. Because they show similar clinical symptoms, distinguishing between them can be difficult. Here, a case of sJIA is reported, which was first misdiagnosed as KD. The patient was a 19-month-old boy who was brought to this hospital 6 days after onset of fever. As he had leukocytosis and elevated C-reactive protein, he was diagnosed presumptively with occult bacteremia. Antibiotic therapy was initiated, but without defervescence. On the eighth day, echocardiographic images showed dilation of the left main trunk of the coronary artery. On the basis of this finding, he was diagnosed as having incomplete KD and high-dose immunoglobulin therapy was initiated. However, the remittent fever persisted, and a non-fixed or evanescent rash was observed. Therefore, the possibility of sJIA complicated by macrophage activation syndrome (MAS) was considered. This was confirmed by the extraordinarily elevated serum interleukin-18 level (44,000 pg/mL; reference value: <500). Steroid pulse therapy without efficacy was then started. He was referred to a pediatric rheumatologist and transferred to a tertiary hospital, where he received tocilizumab administration in addition to steroid pulse therapy, which led to complete remission. These observations suggest that, in cases of intractable KD, even if coronary artery lesions are observed, sJIA complicated by MAS in differential diagnosis should be considered.

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1）Department of Pediatrics, Nabari City Hospital
2）Department of Pediatrics, Kansai Medical University
3）Department of Pediatrics, Kanazawa University

Key words	systemic juvenile idiopathic arthritis, macrophage activation syndrome, coronary arterial lesion, Kawasaki disease, cytokine profile
Received	January 25, 2021
Accepted	April 16, 2021

33 (3)：224─232,2021