Kawasaki disease (KD), or mucocutaneous lymph node syndrome, is an idiopathic, multisystem vasculitis characterized by fever and mucocutaneous inflammation. It has a peak incidence in infants aged 9-11 months and is extremely rare in infants younger than 3 months of age. Most cases occur in individuals who live in East Asia or are of Asian ancestry. Although usually self-limited, potentially life-threatening coronary artery aneurysms may develop in 20%-25% of children without treatment (versus less than 5% with appropriate therapy). Mortality most often occurs within the first weeks to a year after KD due to ischemic heart disease caused by myointimal proliferation within persistent aneurysms. Infants younger than 6 months of age may be at increased risk for aneurysms.
The classic case definition of KD is fever lasting at least 5 days plus the presence of at least 4 of the following principal clinical criteria:
Bilateral bulbar conjunctival injection without exudate
Oral mucosa changes: cracked lips, "strawberry tongue," or diffuse erythema of the mucosae
Changes in the extremities: erythema, induration, or periungual peeling
Exanthem
Cervical lymphadenopathy (greater than 1.5 cm diameter)
Common pitfalls may include diagnosing an infection in an infant with fever and an enlarged cervical lymph node (bacterial lymphadenitis) or sterile pyuria (partially treated urinary tract infection). The subsequent exanthem and mucosal changes may be misdiagnosed as a drug reaction to the prescribed antibiotics.
Viral meningitis may be misdiagnosed in an infant with fever, rash, and cerebrospinal fluid pleocytosis.
Patients with toxic shock syndrome most often have focal cutaneous skin infections, abscesses, infections associated with nasal packing, or a history of recent surgical procedures.
Erythema multiforme presents with symmetrically distributed target lesions. Patients frequently have coexisting herpes orolabialis.
Viral exanthems like measles may be difficult to distinguish from KD. However, patients with measles often display an exudative conjunctivitis and Koplik spots within the oral mucosa.
The cutaneous and mucosal findings in scarlet fever may also easily be confused with KD. However, these patients respond to anti-streptococcal antibiotic therapy.
Distinguishing drug reactions (eg, Stevens-Johnson syndrome) from KD can be difficult. A careful drug history is critical.
KD can present with red cheeks, as does fifth disease (erythema infectiosum). Premature closure on fifth disease leading to missing KD is a diagnostic pitfall.
Reactive infectious mucocutaneous eruption (RIME) – Characterized by prominent mucositis and a sparse eruption that may be polymorphous in association with underlying Mycoplasma pneumoniae or other infection.
