Introduction:
Kawasaki disease (KD) is an acute vasculitis that can rarely be complicated by capillary leak syndrome. Such severe presentations pose major diagnostic challenges due to significant clinical and laboratory overlap with infectious causes of shock, toxic shock syndrome, and other hyperinflammatory conditions, including multisystem inflammatory syndrome in children (MIS-C). Early recognition is essential, as delayed immunomodulatory treatment may result in increased morbidity.
Methods:
Patient data were retrospectively collected from available medical records.
Results:
A previously healthy 12-year-old girl presented with a 6-day history of sore throat, malaise, headache, nonexudative conjunctivitis, watery diarrhea, and a macular rash involving the palms, soles, inguinal, and perigenital regions, and 3 days of high fever. Initial laboratory evaluation demonstrated elevated inflammatory markers (C-reactive protein 226 mg/L, white blood cell count 14.35 ×10⁹/L, erythrocyte sedimentation rate 26 mm/h), mildly elevated liver enzymes, and mild proteinuria and leukocyturia. Electrocardiography, cardiac troponin, and chest radiography were normal. She was hospitalized with suspected KD and empirically treated with amoxicillin–clavulanic acid.
On day 3 of hospitalization, the rash progressed and the patient developed tachycardia and hypotension (80/50 mmHg). Initial echocardiography and abdominal ultrasonography were normal. Due to concern for toxic shock syndrome, antibiotic therapy was changed to flucloxacillin and clindamycin. Follow-up laboratory testing revealed worsening inflammation, hypoalbuminemia (29 g/L), elevated ferritin (617 µg/L), interleukin-6, D-dimer, NT-proBNP, and troponin; hemoglobin was 114 g/L. All microbiological investigations remained negative. Persistent hypotension despite fluid resuscitation necessitated transfer to the pediatric intensive care unit, where inotropic support and supplemental oxygen were required.
Repeat imaging demonstrated left ventricular dilation with mild-to-moderate biventricular dysfunction, mitral regurgitation, and mild pulmonary arterial hypertension, without coronary artery abnormalities. The patient developed pleural effusions, ascites, generalized edema, and a 20% increase in body weight, consistent with capillary leak syndrome. Immunomodulatory therapy with intravenous methylprednisolone, intravenous immunoglobulin, and anakinra resulted in clinical, laboratory, and radiologic improvement. Periungual desquamation developed during convalescence.
Discussion:
This case highlights the diagnostic complexity of KD complicated by capillary leak syndrome and underscores the importance of considering KD in the differential diagnosis of pediatric shock with hyperinflammation to enable timely immunomodulatory therapy and favorable outcomes.