Kawasaki disease is an acute illness primarily affecting young children, characterized by inflammation of blood vessels throughout the body. Also known as mucocutaneous lymph node syndrome, this condition can lead to serious complications, particularly involving the coronary arteries that supply blood to the heart. There is a variant, “atypical Kawasaki disease,” which presents a diagnostic challenge because not all of the typical symptoms are present. Recognizing this incomplete presentation allows for prompt treatment and prevention of severe long-term health issues.
Defining Atypical Kawasaki Disease
Atypical, or incomplete, Kawasaki disease occurs when a child has a persistent fever but fewer than the required classic diagnostic criteria. Classic Kawasaki disease involves a fever lasting at least five days with four of five specific clinical signs, while atypical forms present with only two or three. This incomplete manifestation makes diagnosis difficult, often leading to delays. The term “incomplete” refers to a lack of sufficient classic symptoms, while “atypical” can denote unusual symptoms not typically associated with the disease.
This deviation is common in infants under six months and older children, who often have a higher risk of coronary artery abnormalities. The challenge lies in distinguishing atypical Kawasaki disease from more common childhood illnesses, as its subtle presentation can mimic other conditions.
Recognizing the Signs
Persistent fever remains the most consistent symptom in atypical Kawasaki disease, often lasting five days or longer and showing minimal response to fever-reducing medications. Other signs may appear beyond fever, though they can be subtle, vary, or evolve. These include red or pink eyes without discharge, a rash that can appear on the trunk or groin, and changes in the mouth such as red lips, a “strawberry tongue,” or cracked lips.
Swelling and redness of the hands and feet, sometimes leading to peeling skin around the nails, can also be observed. Swollen lymph nodes, usually in the neck and often unilateral, are another possible sign. These symptoms might not all be present simultaneously, further complicating diagnosis and requiring careful observation.
Diagnostic Process
Diagnosis requires high suspicion, especially in infants prone to incomplete presentations. The diagnosis relies on a combination of persistent fever, some classic signs, and supportive laboratory findings, while also ruling out other potential conditions. Elevated inflammatory markers include a C-reactive protein (CRP) level of 3.0 mg/dL or higher and an erythrocyte sedimentation rate (ESR) of 40 mm/hr or higher.
Other laboratory abnormalities that support the diagnosis include:
An elevated white blood cell count, often greater than 15,000/mm³.
Anemia for the child’s age.
Low albumin levels, typically 3.0 g/dL or less.
Elevated liver enzymes, such as alanine aminotransferase (ALT).
Sterile pyuria, indicated by ten or more white blood cells per high-power field in urine.
Thrombocytosis, an elevated platelet count, which often appears after the seventh day of fever.
Echocardiography also plays a role in assessing for coronary artery involvement, with findings such as a Z-score of 2.5 or greater for the left anterior descending or right coronary arteries suggesting abnormalities.
Treatment and Follow-Up
Early treatment of atypical Kawasaki disease is important to prevent serious complications, especially coronary artery aneurysms. The standard treatment involves intravenous immunoglobulin (IVIG) and aspirin. IVIG, a blood product containing antibodies, helps to reduce inflammation throughout the body. Aspirin helps manage inflammation and prevent blood clot formation, a concern with inflamed coronary arteries.
Prompt IVIG administration, ideally within ten days of fever onset, can significantly reduce the risk of coronary artery aneurysms from approximately 25% to 4-5%. If there is no response to the initial treatment, a second dose of IVIG may be given, sometimes along with corticosteroids or other adjunctive therapies. Long-term follow-up care is also important, particularly if coronary artery abnormalities were detected acutely. This typically includes regular cardiology assessments to monitor heart health and detect late complications.