Summary of "Kawasaki disease ~clinical reasoning~"

Main Ideas and Concepts

Definition and Epidemiology Kawasaki disease is a vasculitis affecting medium-sized arteries, primarily in children aged 1 to 5 years but can also affect teenagers and adults. It is usually self-limited, with fever and acute inflammation lasting around 12 days without treatment.
Clinical Presentation and Diagnostic Criteria (Mnemonic: CRASH) Diagnosis requires fever for at least 5 days plus at least four of the following five clinical features:
- Conjunctival injection: bilateral bulbar conjunctival redness causing photophobia or eye discomfort.
- Rash: polymorphous rash often triggered by sunlight sensitivity.
- Adenopathy: cervical lymphadenopathy, especially anterior cervical nodes over sternocleidomastoid.
- Strawberry tongue and oral mucous membrane changes: injected or fissured lips, injected pharynx.
- Hands and feet changes: erythema, edema, and periungual desquamation.
Additional Symptoms Irritability, rhinorrhea, cough, vomiting, diarrhea, abdominal pain, and joint pain are common but not diagnostic.
Complications The major concern is cardiovascular involvement, particularly coronary artery aneurysms, which can cause arrhythmias, myocardial infarction, and heart failure.
- ECG and Echocardiography are essential for evaluation.
- If Echocardiography is insufficient, CT angiography or MR angiography may be used.
- Stress testing (exercise or dobutamine-induced) is done to assess myocardial perfusion and ischemia in patients with aneurysms.
Incomplete/Atypical Kawasaki disease
- Considered in children with unexplained fever ≥5 days but fewer than four diagnostic criteria, especially infants <6 months with fever ≥7 days.
- Diagnosis requires elevated inflammatory markers (CRP >3 mg/dL, ESR >40 mm/hr) plus ≥3 abnormal supplemental lab findings or abnormal Echocardiography.
- Supplemental labs include:
  - WBC >15,000/µL
  - Platelets >450,000/µL
  - Normocytic normochromic anemia
  - ALT >50 U/L
  - Albumin <3 g/dL
  - Pyuria (>10 WBCs per high-power field in urine)

Management and Treatment

Initial Therapy
- IVIG (Intravenous Immunoglobulin): Single dose of 2 g/kg over 8–12 hours, ideally within the first 10 days of illness.
- IVIG can be given beyond 10 days if there is persistent inflammation (fever, elevated ESR/CRP).
- Aspirin:
  - High dose (30–50 mg/kg/day divided into 4 doses, max 4 g/day) during acute febrile phase.
  - Low dose (3–5 mg/kg/day) continued for about 2 months or longer if coronary artery involvement persists.
Vaccination Considerations
- Aspirin use in children increases risk of Reye syndrome; therefore, varicella and influenza vaccinations are recommended.
- Varicella vaccine should be delayed until 11 months after IVIG due to interference with vaccine efficacy.
Refractory Kawasaki disease
- Defined as persistent or recurrent fever 24 hours after initial IVIG or within 2 weeks post-treatment without another cause.
- Risk factors for IVIG resistance: male sex, age <6 months, high CRP, low sodium, low platelets.
- Management steps:
  1. Repeat IVIG dose (2 g/kg over 8–12 hours).
  2. If still refractory, add glucocorticoids:
    - Pulsed Methylprednisolone (30 mg/kg/day) until response or max 3 doses, or
    - Oral Prednisone (1–2 mg/kg/day) for 15–30 days, divided 2–3 times daily.
- Glucocorticoids are adjunctive due to potential increased risk of coronary aneurysms.