A Missed Kawasaki Disease Shock Syndrome Diagnosis Resulting in Coronary Complications

<i>Background: </i>Kawasaki disease (KD) is an acute inflammatory vasculitis that primarily affects children under 5 years of age. Kawasaki Disease Shock Syndrome (KDSS) is a rare complication characterized by hypotension and shock. Despite being the leading cause of heart disease in developed countries, diagnosing KD is challenging due to the lack of specific pathognomonic tests. Delayed treatment can increase the risk of long-term coronary artery abnormalities in up to 25% of patients. <i>Case presentation: </i>A 31-month-old boy initially presented with fever, lymphadenopathy, and pharyngeal congestion. The patient was treated with antibiotics due to positive Mycoplasma IgM and elevated inflammatory markers. Despite treatment, the patient a widespread rash, ulcers, lip peeling, and orbital swelling. The patient was transferred to the Pediatric Intensive Care Unit of a second hospital as a case of suspected septic shock. The patient received Intravenous immunoglobulin and corticosteroids without a diagnosis of KD. It was not until the 23rd day of illness that KD was diagnosed, and the absence of timely diagnosis resulted in aneurysmal dilation of all major coronary arteries with aneurysmal fusiform formation. <i>Conclusion: </i>The case highlights the importance of early recognition and diagnosis of KD and KDSS, recommending multidisciplinary evaluation. Clinicians should consider atypical KD in children who are unresponsive to antibiotics and have persistent fever. Positive infectious serology does not exclude the diagnosis of KD. In the absence of echocardiographic markers, early treatment should be prioritized to prevent long-term cardiac damage.