Letters to the Editor

22 April 2008 Dear Editor, COMMENT ON FAILURE TO DISTINGUISH SYSTEMIC-ONSET JUVENILE IDIOPATHIC ARTHRITIS FROM INCOMPLETE KAWASAKI DISEASE IN AN INFANT We read with interest the article ‘Failure to distinguish systemic-onset juvenile idiopathic arthritis from incomplete Kawasaki disease in an infant’ by Komatsu et al.1 They reported an infant who had initially been diagnosed as having incomplete Kawasaki disease (KD) according to the American Heart Association guidelines, but the diagnosis of systemic-onset juvenile idiopathic arthritis (JIA) was established later.1 It is very difficult to differentiate systemic JIA from incomplete KD at an early stage of the disease because of various similar symptoms between the two diseases. Regarding this issue, we believe that one recent study by Binstadt et al.2 would give important information on differential diagnoses or appropriate therapeutic approach. According to their study, coronary artery dilation was observed in 5 of the 12 patients with systemic JIA who had echocardiograms performed at the time of presentation with fever; 2 of the 5 patients with coronary artery dilatation also fulfilled the clinical criteria for KD, suggesting that transient coronary artery dilation might occur early in the course of systemic JIA, or KD might trigger or evolve into systemic JIA.2 Therefore, Binstadt et al. suggested that appropriate therapy with intravenous immunoglobulins and aspirin should be instituted if a patient meets the criteria for KD, and careful follow-up monitoring might be necessary to document the resolution of symptoms after treatment for KD because persistence of fever with the development of frank arthritis should alert physicians to the possibility of systemic JIA.2 Because Silverman et al. showed that intravenous immunoglobulin therapy was also beneficial in the treatment of systemic JIA,3 we think that this therapy should not be delayed when a patient shows prolonged fever, rash and cervical lymphadenopathy. Although Binstadt et al. could not identify any clinical, laboratory and echocardiographic findings that would distinguish patients with acute KD from those with early systemic JIA,2 Maeno et al. recently reported that serum levels of interleukin-18 (IL-18) were highly elevated in systemic JIA but not in other subtypes of JIA or in KD, suggesting serum IL-18 levels might be useful in differentiating these two inflammatory diseases.4 Therefore, they speculated that development of strategies for neutralization of IL-18 inflammatory activities might lead to a more satisfactory treatment of systemic JIA, as was accomplished with Tumor Necrosis Factor (TNF)-α in rheumatoid arthritis.4 In conclusion, we recommend that both KD and systemic JIA should be considered when a child present with prolonged fever, rash and cervical lymphadenopathy, as suggested by Binstadt et al.2, and further studies should be performed to identify biological markers to differentiate between the two diseases at an early stage of the disease.