Needing a Diagnostic Kick-start

Kawasaki disease

Also known as Mucocutaneous Lymph Node Syndrome, this vasculitic disorder was first described by Dr. Tomisaku Kawaski in 1967. It is of uncertain etiology, but may be a post-infectious condition.

The diagnosis is made on the basis of the following clinical criteria (A + B):

A.Fever ≥5 days

B. At least 4 of the 5 following physical examination findings:

1. Bilateral, nonexudative bulbar conjunctival injection. Bilateral scleral injection with perilimbic sparing
2. Oropharyngeal mucous membrane changes. Pharyngeal erythema, red/cracked lips, and a strawberry tongue
3. Cervical lymphadenopathy. With at least one node >1.5 cm in diameter.
4. Peripheral extremity changes 
The diffuse palmar erythema seen in KD is in contrast to the discrete macular lesions of various viral illnesses (e.g., measles) that can sometimes be seen on the palms and soles.
– acute phase: diffuse erythema and swelling of the hands and feet.
– convalescent phase: periungual desquamation (weeks 2 to 3)
5. A polymorphous generalized rash. Nonvesicular and nonbullous. There is no specific rash that is pathognomonic for KD

The manifestations may appear sequentially rather than concurrently. Atypical cases may not meet all the criteria but may still have the same risks of cardiac complications. These ‘incomplete’ cases occur more often in infants less than 6 months-old — further investigations (see Q5) should be performed if fever of 5 days and 2 or 3 of the other criteria are present.

Clinicians should have a high index of suspicion for this diagnosis in any child with a prolonged fever as early diagnosis and treatment may help prevent the potentially fatal complications of Kawasaki disease.

The approach to ‘incomplete’ Kawasaki disease is summarised nicely in this Paucis Verbis card from Academic Life in Emergency Medicine: Kawasaki disease.

Physical findings consistent with Kawasaki disease

Kawasaki disease may occur in any child of any age, and even adults in some cases.

However, it is more common in:

• children aged < 5 years
• Asians
• males (RR 1.5)

Diagnosis may be difficult as Kawasaki disease may mimic a number of other conditions:

• Viral exanthemas including measles
• Streptococcal disease (e.g. scarlet fever, toxic shock syndrome)
• Staphylococcal disease (e.g. scalded skin syndrome, toxic shock syndrome)
• Bilateral cervical lymphadenitis
• Leptospirosis and rickettsial diseases
• Stevens-Johnson syndrome and Toxic Epidermal Necrolysis
• Drug reactions including mercury hypersensitivty reaction
• Juvenile Chronic Arthritis

Echocardiography

The most important investigation to assess for cardiac complications. If no abnormalities on presentation the study should be repeated in 4-6 weeks.

Laboratory tests:

• Rule out other causes:
  • ASOT, AntiDNAse B, throat swabs, blood cultures
• Non-specific findings seen in KD include:
  • FBC: normochromic anemia and leukocytosis; thrombocytosis (in the 2nd week)
  • LFT changes and hypoalbuminemia
  • increased CRP and ESR
  • Sterile pyuria of ≥10 WBCs per high-power field

The approach to ‘incomplete’ Kawasaki disease is summarised nicely in this Paucis Verbis card from Academic Life in Emergency Medicine: Kawasaki disease.

Cardiac complications:

• Carditis during the febrile phase
  • myocarditis with ST-T changes (25%), pericardial effusions (20-40%), valvular dysfunction (1-2%) and cardiac failure (~5%)
• Coronary vessel abnormalities (occur in 20% of cases if untreated and <5% if treated; peaks at 2-4 weeks)
  • aneurysm formation may lead to fatalities from thrombosis, rupture or ischemia-related dysrhythmia (usually within 6 weeks of onset, but may occur many years later.

Kawasaki disease is a vasculitis that can potentially affect almost any organ, it is commonly associated with:

• arthritis
• keratitis and uveitis
• diarrhoea, vomiting and gallbladder disease
• coryza and cough

IV immunoglobulin and aspirin

IV immunoglobulin

• 2g/kg IV over 10 hours
• ideally start within 10 days of the onset of the illness
• a second dose may be given if fevers persist

Aspirin

• 3-5 mg/kg PO daily for 6-8 weeks (when laboratory parameters have fully normalised)
• some advise higher doses of aspirin until the patient is afebrile or 48-72 hours, but others argue this offers no benefit in addition to treatment with IV immunoglobulin.

Despite these therapies 2-4% of cases still go on to develop coronary artery abnormalities. Corticosteroids may be considered in refractory cases, although there is little evidence supporting their use.