Inflammatory Syndromes

Case 4. AT is a 4-year-old patient of Japanese descent who is brought to your office by his parents after 5 days of fever. On examination, he has conjunctival injection; red, cracked lips and strawberry tongue; swollen and erythematous hands and feet; and cervical lymphadenopathy. You suspect he has Kawasaki disease or multisystem inflammatory syndrome in children (MIS-C).

Kawasaki disease is an acute vasculitis that occurs in children.¹ It presents as a self-limited febrile disease that leads to cardiac artery aneurysms in up to 25% of untreated children. Kawasaki disease primarily affects children younger than 5 years with an annual incidence in the United States of approximately 25 out of 100,000 children in that age range.² It is approximately 10 times more common in Japan (243-266 per 100,000 children younger than 5 years).¹ In the United States it is more common among children of Asian, specifically Japanese, and Pacific Island heritage.^1,3 It is 50% more common in males than females (1.5:1 ratio) and occurs more often in winter and early spring in North America.¹

The cause of Kawasaki disease remains unknown, but it is thought to be an inflammatory immune response to an antigen that results in immunity for future exposures.¹ A novel RNA respiratory virus has been proposed as a possible antigen. A study of seasonal high-altitude wind patterns suggests that the antigen is spread across the Pacific area, potentially causing the seasonal pattern.⁴

Kawasaki disease remains a clinical diagnosis, and although inflammatory markers may support the diagnosis, there are no definitive diagnostic tests.¹ The diagnosis is made based on the presence of a fever for 5 days or more and at least four of the five principal clinical features: extremity changes, rash, bilateral conjunctival injection sparing the limbus, oral changes, and cervical lymphadenopathy. Images of typical clinical findings are available through the Kawasaki Disease Foundation.⁵

The presence of fever and only two or three clinical features can be considered incomplete Kawasaki disease, and laboratory evaluation may support the diagnosis.¹ The finding of coronary artery aneurysms on echocardiogram confirms the diagnosis of incomplete Kawasaki disease,¹ but such findings typically are not present early in the course of the disease. Incomplete Kawasaki disease is more common in infants (younger than 12 months), who are at higher risk for cardiac complications.