Incomplete Kawasaki Disease on a 4 Month Old Child: When Fever is the only Clinical Sign

Background: Kawasaki disease (KD) is one of the most common vasculitis of childhood and remains the main cause of acquired heart disease in children in developed countries. It most commonly (90%) affects children before 5 years of age and less frequently (10%) before 6 months of age. The pathophysiology is still unknown, but immunologic factors appear to play an important role.

Objective: We present a case that highlights the importance of clinical suspicion of KD, even in the small infant.

Methods – case report: A four-month-old female infant was admitted for fever and irritability for 5 days. Vaccination with Meningococcal Group B Vaccine had been instituted 2 days before the show of symptoms. On admission, there were no remarkable physical findings. Laboratory evaluation showed elevated white blood cell count (WBC) and C Reactive Protein (CRP), urinalysis was normal. Blood and urine cultures were obtained and intravenous Ceftriaxone was started. On the 4th day of admission the patient was afebrile, but because of maintained irritability and tympanic temperatures constantly above 37.5 ºC, laboratory evaluation was repeated. WBC and CRP values remained elevated, now with associated thrombocytosis and elevated liver enzyme values. Cultures showed no bacterial growth. On the 8^th day, due to the maintained clinical status, laboratory evaluation was once again repeated, and continued to show a rise of the inflammatory markers. KD was considered and echocardiographic evaluation was performed, showing diffuse ectasia of the right coronary arteries (3mm). Treatment with IV immunoglobulin and acetylsalicylic acid was started, with clinical improvement.

Conclusion: KD remains an infrequent illness before 4 months of age and its aetiology a cause of debate. This case report highlights the importance of clinical suspicion of KD, even when fever is the only positive diagnostic criteria.