Rheumatology: Kawasaki Disease & Rheumatic Fever Flashcards
What is Kawasaki disease?
An acute self-limiting systemic vasculitis of unknown cause that mainly affects children <5 (but can affect children of any age, including infants and teenagers).
It is a medium-sized artery vasculitis, particularly affecting the coronary arteries.
Which ethnicity does Kawasaki disease affect most?
Children of East Asian origin.
What arteries does Kawasaki disease particularly affect?
Coronary arteries
What are 3 risk factors for Kawasaki disease?
1) Asian ethnicity, especially Japanese
2) Aged <5 years (80% of cases occur in those under the age of five)
3) Male sex (male to female ratio 1.5:1)
Who should Kawasaki disease be considered in?
Any child with a fever lasting ≥5 days.
How is Kawasaki disease diagnosed?
It is a clinical diagnosis, and there is no diagnostic test.
What is the diagnosis of Kawasaki disease based on?
The American Heart Association diagnostic criteria.
What is the American Heart Association diagnostic criteria for Kawasaki disease?
Presence of fever (usually ≥39°C) for at least 5 days, plus at least 4 out of 5 key features:
1) Mucositis: erythema and cracking of the lips, strawberry tongue and/or oral erythema
2) Conjunctivitis: bilateral conjunctivitis without exudate
3) Rash: maculopapular, erythroderma or erythema multiforme
4) Peripheral changes: erythema, oedema and/or desquamation of the hands and feet
5) Cervical lymphadenopathy
What are the clinical features of Kawasaki disease?
1) High-grade fever which lasts for > 5 days –> characteristically resistant to antipyretics
2) Conjunctival injection
3) Bright red, cracked lips
4) Strawberry rongue
5) Cervical lymphadenopathy
6) Red palms of the hands and the soles of the feet which later peel
What 3 phases does Kawasaki disease usually follow?
1) Acute phase (1-2 weeks from fever onset)
2) Subacute phase (2-4 weeks from fever onset)
3) Convalescent phase (8 weeks from fever onset)
Describe the acute phase of Kawasaki disease
1-2 weeks from fever onset.
Symptoms –> High fever, irritability, rash, mucositis, peripheral erythema and oedema.
Describe the subacute phase of Kawasaki disease
2-4 weeks from fever onset.
Symptoms –> afebrile, most clinical features begin to resolve, desquamation of the hands and feet.
Which phase of Kawasaki disease is the highest risk period for developing cardiac complications?
Subacute phase (2-4 weeks from fever onset)
Which phase of Kawasaki disease can you see desquamation of the hands and feet?
Subacute phase (2-4 weeks from fever onset)
Describe the convalescent phase of Kawasaki disease
4-8 weeks from fever onset.
Asymptomatic period, clinical features have resolved.
Coronary artery aneurysms often improve but may get worse.
Give 5 differentials for Kawasaki disease
Fever is a common paediatric presentation.
1) Scarlet fever or acute rheumatic fever (Group A streptococcus)
2) Toxic shock syndrome or staphylococcal scalded skin syndrome (Staph aureus)
3) Measles
4) Steven-Johnson syndrome / toxic epidermal necrolysis
5) Systemic-onset juvenile idiopathic arthritis
What investigations may be relevant in Kawasaki disease?
1) ECG: may show arrhythmias or ST-T changes if myocarditis or myocardial infarction occurs
2) Urinalysis: may show sterile pyuria
3) Baseline blood tests (FBC, U&E, LFTs): there may be anaemia, raised white cells and raised platelets. LFTs may be deranged if hepatitis occurs.
4) ESR and/or CRP: often significantly raised
5) Anti-streptolysin O titre (ASOT): to exclude group A streptococcal infection
What investigation is ESSENTIAL in Kawasaki disease?
Echocardiogram
What is a key complication of Kawasaki disease?
Coronary artery aneurysm –> get an echo !
When should an echo be performed in Kawasaki disease?
It should be performed as soon as Kawasaki disease is suspected but should not delay treatment (e.g. if the child presents out-of-hours or to a hospital without a suitably qualified sonographer).
What may be some findings on an echo in Kawasaki disease?
1) Coronary artery aneurysms
2) Valvular disease (e.g. mitral regurgitation)
3) Coronary artery thrombosis
4) Poor ventricular function/evidence of myocarditis
5) Pericardial effusion/evidence of pericarditis
Does a normal echo rule out Kawasaki disease?
No - the echocardiogram can be normal in the first week of the disease
Management of Kawasaki disease?
Admit to hospital
Mainstay of treatment –> oral aspirin (high dose) and IV immunoglobulin.
Role of aspirin in Kawasaki disease?
Aspirin is thought to reduce the risk of coronary artery aneurysms and thrombosis through its antiplatelet and anti-inflammatory effects.
How long is aspirin given for in Kawasaki disease?
Typically, high-dose aspirin is given until the fever has resolved for 48 hours, then low-dose aspirin for approximately 6 weeks (duration will be guided by cardiology).
Why is aspirin usually contraindicated in children <16?
Due to risk of Reye’s syndrome.
However, in Kawasaki disease, the benefits are felt to outweigh this risk.
What is Reye’s syndrome?
A rare acute encephalopathy associated with liver failure.
Role of IV immunoglobulin in Kawasaki disease?
An infusion of IVIG within the first 10 days of illness can reduce the incidence of coronary artery aneurysms.
When should improvement be seen after intiating treatment in Kawasaki disease?
Within 36 hours.
Note - A second dose of IVIG may be given if an improvement is not seen.
What can be used in refratory cases of Kawasaki disease?
Other treatments, including corticosteroids or infliximab (an anti-TNF agent), may be used in refractory cases or in those with risk factors for IVIG resistance.
What are some complications of Kawasaki disease?
1) Coronary artery aneurysms
2) Myocarditis/pericarditis
3) Arrhythmias
4) Valvular disease (e.g. mitral regurgitation)
5) Coronary artery thrombosis/myocardial infarction
6) Sudden cardiac death
What is the danger of a coronary artery aneurysm in Kawasaki disease?
Giant aneurysms may rupture, causing cardiac tamponade.
What % of children with Kawasaki disease develop a coronary artery aneurysm?
15-25% of untreated children develop aneurysms, but the risk is much lower with early treatment.
What is rheumatic fever?
A systemic inflammatory disorder that arises as a complication following infection with group A Strep (S. pyogenes).
How soon after Strep infection can rheumatic fever develop?
2-6 weeks
Is rheumatic fever contagious?
No, unlike the initial infection.
What age does rheumatic fever typically affect?
Rheumatic fever typically affects children between the ages of 5 and 15, with girls being affected slightly more commonly than boys.
How does initial Strep. pyogenes infection typically present?
- Pharyngitis (sore throat)
- Can also present as cellulitis