Exploring Kawasaki Disease

A relatively late manifestation is sheet-like desquamation, beginning at the tips of the fingers or toes.

The differential diagnosis of KD (Table 1) is dominated by infectious illnesses commonly seen in childhood. Systemic onset juvenile idiopathic arthritis that is characterized by fever, rash and elevated inflammatory markers can be confused with KD, and in fact, coronary artery dimensions may be enlarged in some of these children. The toxic shock syndromes associated with Streptococcus and Staphylococcus may also mimic KD, although the multisystem involvement can provide clues to a diagnosis other than KD. Stevens-Johnson syndrome and drug hypersensitivity reaction are also on the differential diagnosis, as is the least common mimic, mercury poisoning.

Cardiac Involvement in KD

Echocardiography is the imaging modality of choice in KD, because the coronary arteries in children can be easily visualized with this noninvasive method. Measure­ments from the inner edge to inner edge of the left main coronary artery (LMCA), left anterior descending artery (LAD), right coronary artery (RCA), left circumflex and posterior descending coronary artery should be assessed. The Japanese Ministry of Health has defined abnormal coronary arteries as greater than 3 mm if the child is younger than 5 years old, and greater than 4 mm if the child is 5 years or older, if the internal diameter is 1.5 times larger than its adjacent segment, or if the lumen is clearly irregular. Because coronary artery dimensions are predicated on the size of the child, coronary artery size adjusted for body surface area, or z scores, are available for the LMCA, proximal LAD and proximal RCA. Because z scores are not available for all coronary artery segments, the Japanese Ministry of Health guidelines are useful in assessing the remainder of the coronary arteries. Lack of tapering of the coronary arteries, left ventricular dysfunction, valvular regurgitation, pericardial effusion and z scores greater than 2.0 may be considered supportive of the diagnosis.

Echocardiograms should be obtained at the time of diagnosis, at approximately two weeks and at six weeks following disease onset if there has been no evidence of coronary artery involvement. Children with coronary artery abnormalities may require more frequent monitoring and should be managed by a pediatric cardiologist. Other imaging modalities, such as CT angiograms, MR angiography or conventional angiography should be decided on a case-by-case basis.

Note the fissured, erythematous and desquamated lips in this 2-year-old girl with Kawasaki disease.

Treatment

Standard treatment for KD includes IVIG and aspirin (ASA). IVIG is given at high doses (2 grams/kg) and should be administered slowly over 8–12 hours to avoid hemodynamic instability. The mechanism by which IVIG effectively treats KD is unclear, but it reduces the risk of coronary artery abnormalities from 20–25% to less than 5%.² The role of ASA in treating KD is controversial, because studies have shown that it does not influence coronary artery outcomes.¹³ There is also variation in practice regarding the dosing and duration of ASA. High, anti-inflammatory doses of ASA (80–100 mg/kg/day divided four times per day) are given in North America at least until the child is afebrile for 48 hours followed by low, antiplatelet dosing (3–5 mg/kg/day) for a minimum of six weeks. However, other centers administer high-dose ASA until Day 14 of illness, before switching to low-dose ASA.