USMLE Guide: Kawasaki Disease

Overview

Kawasaki Disease (KD), also known as Kawasaki syndrome, is an acute febrile illness that primarily affects children under the age of 5. It is characterized by inflammation of medium-sized arteries throughout the body, with a particular affinity for the coronary arteries. KD is a leading cause of acquired heart disease in children in developed countries.

Etiology

The exact cause of kawasaki disease is unknown. However, it is believed to involve an abnormal immune response triggered by an infectious agent in genetically susceptible individuals. Various theories suggest viral or bacterial infections as the potential triggers, but no specific pathogen has been identified.

Clinical Presentation

1. Fever: Persistent high-grade fever (>5 days) is the hallmark feature of KD.
2. Conjunctivitis: Bilateral non-exudative conjunctival injection is a common finding.
3. Mucous Membrane Changes: Red, cracked lips; strawberry tongue; and diffuse erythema of the oral mucosa are often observed.
4. Rash: A polymorphous rash, commonly described as maculopapular or morbilliform, appears during the acute phase.
5. Extremity Changes: Peripheral edema, erythema, and desquamation of the palms and soles occur in the subacute phase.
6. Cervical Lymphadenopathy: Unilateral usually, non-suppurative, and >1.5 cm in diameter lymph nodes are commonly palpated.

Complications

1. Coronary Artery Aneurysm: The most serious complication of KD is the development of coronary artery aneurysms, which can lead to myocardial infarction, ischemic heart disease, or sudden death.
2. Myocarditis: Inflammation of the heart muscle can cause myocardial dysfunction.
3. Arrhythmias: Irregular heart rhythms can result from myocardial involvement.
4. Pericarditis: Inflammation of the pericardium can lead to pericardial effusion or cardiac tamponade.
5. Systemic Vasculitis: Involvement of other medium-sized arteries can result in vasculitis in various organs, leading to complications such as hepatobiliary dysfunction, aseptic meningitis, or renal impairment.

Diagnosis

Kawasaki Disease is a clinical diagnosis based on characteristic findings. The American Heart Association (AHA) has established diagnostic criteria, which include fever lasting >5 days and at least four of the following features:

1. Changes in lips and oral cavity
2. Non-exudative conjunctival injection
3. Changes in extremities
4. Polymorphous rash
5. Cervical lymphadenopathy

Management

1. Intravenous Immunoglobulin (IVIG): Administration of high-dose IVIG within the first 10 days of illness reduces the risk of coronary artery aneurysms and other complications.
2. Aspirin: High-dose aspirin is given until the patient becomes afebrile, then low-dose aspirin therapy is continued for several weeks to prevent thrombosis.
3. Monitoring: Regular follow-up with serial echocardiograms is crucial to assess coronary artery involvement and guide further management.

Prognosis

With prompt treatment, the prognosis of Kawasaki Disease is generally good. The majority of patients recover completely without sequelae. However, individuals with coronary artery involvement require long-term monitoring, as they are at risk of developing ischemic heart disease or other cardiovascular complications later in life.

Conclusion

Kawasaki Disease is an important condition to recognize due to its potential to cause coronary artery aneurysms and other serious complications. Familiarity with the diagnostic criteria and appropriate management, including IVIG administration and aspirin therapy, is crucial for physicians caring for pediatric patients. Early recognition and intervention significantly improve outcomes for children with KD.