Incomplete Kawasaki Disease: A Diagnostic Challenge

Background: Kawasaki disease (KD) is an acute inflammatory vasculitis defined by clinical criteria. Coronary artery (CA) aneurysms may occur, leading to significant morbidity and mortality. Young infants are at increased risk, as prevalent incomplete forms pose diagnostic difficulties that often delay timely treatment.

Objective: This work aims to raise awareness to incomplete KD trough a clinical case, highlighting its complexities.

Clinical Case: Previously healthy 6 month-old female admitted with high fever, rhinorrhea, cough and irritability for 4 days. Besides bilateral ocular hyperaemia, the remaining physical examination was unremarkable. Laboratory tests showed leukocytosis with neutrophilia, C-reative protein 128 mg/L, mild normocytic normochromic anaemia and significant leukocyturia. Lumbar puncture revealed limpid liquor with pleocytosis (414/uL) and normal biochemistry. Ceftriaxone was initiated. During hospitalization, intermittent polymorphous exanthema, hands and feet oedema were observed. Persistent fever, fluctuant after day 5, and irritability accounted for progressive therapeutic escalation with vancomycin and meropenem whilst awainting for a positive result of liquor bacterial DNA; after confirmed contamination, anphotericin B was started. Repeated and extensive blood, urine, liquor and respiratory secretions studies showed no evidence of causative infectious agent. Electroencephalogram was normal. Other analytic findings: thrombocytosis, hypoalbuminemia and sedimentation rate 111mm/h. At day 16 after admission, an echocardiogram revealed left and right coronary ectasia, and KD was confirmed. She received intravenous immunoglobulin, methylprednisolone, high-dose oral acetylsalicylic acid (ASA) 60mg/kg/day, with further favourable clinical and analytic evolution. Periungual desquamation was noticed during 3^rd week. She was discharged for ambulatory follow-up after 28 days, with oral ASA (low dose).

Conclusion: Incomplete KD is a clinical challenge, especially in infants. Heterogeneous laboratory findings and unspecific clinical features may be misleading. A high index suspicion is fundamental, as correct diagnosis might rest upon detection of CA abnormalities. Prompt adequate treatment has a potential prognosis impact, besides limiting further futile therapeutic interventions.