Kawasaki disease vs Scarlet fever
How to tell Kawasaki disease and Scarlet fever apart when a board question makes them look alike.
Step 2 CK pairs are in open beta while clinical review finishes. Spot an issue? Tell us.
Fever lasting at least 5 days with nonpurulent conjunctivitis is the quickest discriminator for Kawasaki disease.
Side by side
Fever for at least 5 days with bilateral nonpurulent conjunctivitis, mucosal changes, extremity edema or desquamation, polymorphous rash, and cervical adenopathy indicates Kawasaki disease.
Acute streptococcal pharyngitis with sandpaper rash, strawberry tongue, and Pastia lines indicates scarlet fever.
A medium-vessel vasculitis causes systemic inflammation and can produce coronary artery aneurysms without timely treatment.
Group A streptococcal pyrogenic exotoxins trigger diffuse erythematous rash in the setting of pharyngeal infection.
Inflammatory markers are elevated, platelets often rise after day 7, and echocardiography is required to evaluate coronary artery involvement at diagnosis and follow-up.
Rapid antigen test or throat culture confirms group A streptococcus; leukocytosis may be present but coronary imaging is not part of routine scarlet fever care.
The trap
A child with strawberry tongue and rash is treated as scarlet fever alone despite prolonged fever and conjunctivitis; this delay misses the IVIG window that lowers coronary aneurysm risk in Kawasaki disease.
The repair move
Next best step: if Kawasaki criteria are met, give IVIG 2 g/kg as a single infusion within 10 days of fever onset and start high-dose aspirin 80 to 100 mg/kg/day divided every 6 hours until afebrile for 48 to 72 hours, then transition to 3 to 5 mg/kg/day. Obtain baseline echocardiogram and repeat at 1 to 2 weeks and 4 to 6 weeks. If scarlet fever is confirmed without Kawasaki features, treat with penicillin V or amoxicillin for 10 days.
Try a free question
CoreA 4-year-old girl has 6 days of fever, bilateral nonpurulent conjunctivitis, cracked lips, and swelling of hands and feet. BP 94/56 mm Hg, HR 132/min, temp 39.2 C. What is the next best step in management?
Show answer and explanation
Answer: A. Administer IVIG and high-dose aspirin. This child meets classic Kawasaki criteria and requires immediate IVIG plus aspirin to reduce coronary complications.
Why the other choices are tempting
- B. Wrong because antibiotic-only treatment misses vasculitis and coronary risk.
- C. Wrong because delayed treatment increases aneurysm risk.
- D. Wrong because steroid monotherapy is not first-line initial therapy for classic cases.
- E. Wrong because topical treatment does not address systemic inflammation.
Flashcards
Tap a card to flip it.
What fever duration threshold should trigger Kawasaki disease consideration in a child with rash and mucosal changes?
Fever for at least 5 days is required for classic Kawasaki disease diagnosis criteria.
Which conjunctival finding favors Kawasaki disease over scarlet fever?
Bilateral nonpurulent conjunctivitis strongly supports Kawasaki disease.
Quick answers
What is the fastest way to tell Kawasaki disease from Scarlet fever?
Fever lasting at least 5 days with nonpurulent conjunctivitis is the quickest discriminator for Kawasaki disease.
What is the key clue for Kawasaki disease?
Fever for at least 5 days with bilateral nonpurulent conjunctivitis, mucosal changes, extremity edema or desquamation, polymorphous rash, and cervical adenopathy indicates Kawasaki disease.
What is the key clue for Scarlet fever?
Acute streptococcal pharyngitis with sandpaper rash, strawberry tongue, and Pastia lines indicates scarlet fever.
What is the common trap with Kawasaki disease vs Scarlet fever?
A child with strawberry tongue and rash is treated as scarlet fever alone despite prolonged fever and conjunctivitis; this delay misses the IVIG window that lowers coronary aneurysm risk in Kawasaki disease.