Kawasaki Disease (KD)
Kawasaki disease is a systemic vasculitis that primarily affects medium-sized arteries, most notably the coronary arteries. It is the leading cause of acquired heart disease in children in developed countries. A high index of suspicion is essential to prevent long-term complications, such as coronary artery aneurysms.
Diagnosis
The diagnosis of Kawasaki disease is clinical and is made when a child has a fever for at least 5 days along with at least 4 of the following 5 features:
Eyes: Bilateral, non-exudative conjunctivitis.
Mouth: Red, cracked lips and/or a “strawberry tongue”.
Neck: Cervical lymphadenopathy, typically unilateral, with a lymph node larger than 1.5 cm.
Skin: A diffuse maculopapular or urticarial rash.
Hands and Feet: Erythema and oedema of the hands and feet, followed by desquamation (peeling) of the fingers and toes.
Incomplete or Atypical KD
It’s important to recognise incomplete or atypical Kawasaki disease, which may not meet the full diagnostic criteria but still carries a risk of coronary artery disease. This should be considered in any child with a prolonged fever and raised inflammatory markers.
Note: Diagnosis requires at least 5 days of fever and any 4 of recognition features; however
► KD can now be diagnosed with 4days of fever when 4 features are present (particularly if erythema and oedema of hands / feet).
► KD should be considered even if fever resolves after 7days without treatment.
► KD should also be considered in:
- Infants under 6 months of age with prolonged fever and irritability.
- Infants with prolonged fever and aseptic meningitis.
- Infants or children with prolonged fever plus unexplained lymphadenitis, retrotonsillar collection or shock.
Investigations
Bloods:
Full Blood Count (FBC): A raised platelet count is a characteristic finding but typically occurs after the first week of illness.
- KD can be excluded if CRP, ESR and platelet count are normal after 7 days of fever.
Inflammatory Markers: Both C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) are significantly elevated.
- ESR becomes uninterpretable after administering IVIG.
Echocardiogram (ECHO): An echocardiogram is the most crucial investigation.
A baseline ECHO should be performed as soon as the diagnosis is suspected to assess for coronary artery involvement.
Repeat ECHO is required at 6 weeks to monitor for the development of aneurysms.
Echocardiography is not a diagnostic test for KD, so do not delay treatment if ECHO is unavailable or is normal.
Coronary artery abnormality is not usually detectable until after 7 days of illness.
Coronary artery internal diameter z-score greater than or equal to 2.5 is highly specific for KD.
If KD suspected, do ECHO within 1–2 weeks, and then 4–6 weeks after initial treatment; if both normal then no further imaging needed.
Other Tests: A urinalysis and an ECG should also be performed.
Management
The management of Kawasaki disease is a medical emergency aimed at reducing inflammation and preventing progressin of coronary artery damage.
Intravenous Immunoglobulin (IVIG): IVIG is the cornerstone of treatment and should be administered as a single dose (2 g/kg) as soon as the diagnosis is made. It has been shown to significantly reduce the risk of coronary artery aneurysms.
Aspirin: High-dose aspirin (30-50 mg/kg/day) is started alongside IVIG and continued until the child is afebrile. The dose is then reduced to a low, antiplatelet dose (3-5 mg/kg/day) and continued for 6-8 weeks or until inflammatory markers normalise.
Refractory KD: In cases that do not respond to initial IVIG treatment, a second dose of IVIG, corticosteroids, or other biological agents may be considered.
Long-Term Follow-up: Children who have had Kawasaki disease, particularly those with coronary artery involvement, require long-term cardiology follow-up to monitor for the development of aneurysms. Serial echocardiography and cardiology follow-up are recommended to monitor for changes in cardiac function and/or coronary vessels.
Live Vaccines: Children who receive IVIG must have their live vaccines, such as MMR, deferred for up to 11 months, as the IVIG can interfere with the vaccine’s efficacy.