A Case of Refractory Kawasaki Disease With Yersinia pseudotuberculosis Infection Successfully Treated With Cefotaxime Following Immunosuppressive Therapy.

Kawasaki disease (KD) is a vasculitis mainly affecting children under five, with symptoms such as persistent fever, rash, red lips, strawberry tongue, conjunctivitis, and swollen hands and feet. Diagnosis is based on a fever lasting over five days plus at least four of these symptoms. Treatment includes intravenous immunoglobulin (IVIG) and aspirin to reduce complications, especially coronary artery issues.  infection is a gram-negative bacterium. In KD patients, the most prevalent gastrointestinal symptoms were vomiting (28.9%), abdominal pain (17.4%), and diarrhea (16.9%). By contrast, diarrhea is observed in over 50% of patients with  infection.  is a gram-negative bacterium reported to infect a wide variety of animal hosts and contact with these animals can serve as a potential clue in diagnosis.  infection can mimic KD with similar fever and rash symptoms, posing a diagnostic challenge. In practice, however, differentiation remains challenging. Differentiating between KD and  is essential, especially in cases resistant to typical KD treatment. Distinguishing KD from  infection in clinical practice is crucial to prevent misdiagnosis, avoid unnecessary immunosuppression, and minimize delays in effective treatment. Misinterpreting  infection as KD may lead to inappropriate treatment strategies that fail to address the underlying infection, potentially resulting in adverse patient outcomes. Accurate and timely diagnosis is therefore essential to initiate appropriate therapeutic interventions. A 16-month-old boy presented with fever and diarrhea and was initially treated for infectious gastroenteritis, with elevated inflammatory markers noted (C-reactive protein (CRP) 4.47 mg/dL, white blood cell (WBC) 8,200/μL). As his condition progressed, he developed symptoms consistent with KD, including a rash and mucous membrane changes, and was treated with IVIG and aspirin. However, the fever persisted, and elevated inflammatory markers continued (CRP 3.93 mg/dL, WBC 9,700/μL), prompting additional immunosuppressive therapies for refractory KD. Ultrasound revealed gastrointestinal and lymph node abnormalities suggestive of vasculitis. Eventually, infection was confirmed through serology, and antibiotic treatment was reintroduced, leading to defervescence. This case highlights the challenge of distinguishing KD from infection because they can coexist, complicating treatment decisions. Rapid diagnostic methods for , specifically through loop-mediated isothermal amplification-polymerase chain reaction (LAMP-PCR) testing, are crucial to guide timely treatment, particularly given the risk of coronary artery complications associated with both conditions.