Lack of elevated inflammatory markers (CRP is less than 3 mg/dl and ESR is less than 40 mm/hr) and the presence of two or three principal clinical features warrant ongoing daily monitoring of ESR, CRP, and fever until day seven of illness. If the fever resolves but is followed by peeling of extremities, an echocardiogram should be done. Lumbar puncture might help differentiate from CNS infectious etiologies, but about 50% of KD patients have a cerebrospinal fluid pleocytosis.
Echocardiography is the preferred imaging modality for the initial cardiovascular evaluation and follow-up.1 It has a sensitivity of 100% and specificity of 96% for the detection of proximal coronary aneurysms.13 Coronary aneurysms are clinically silent in most cases and can manifest with delayed complications, such as myocardial infarction or sudden death. Imaging plays an important role in the early diagnosis of these aneurysms and in estimating their number, size, and location, important elements in making a therapeutic decision.14
Although the echocardiography should be done as soon as KD is suspected, definitive treatment must not be delayed. Evaluation of all coronary artery segments, as well as cardiac contractility and presence of effusion, should be noted on echocardiography. In the absence of complications, echocardiography is performed at the time of diagnosis and at two weeks and six to eight weeks after disease onset.11
Treatment
Treatment goals for Kawasaki disease in the acute phase are reduction of systemic and coronary arterial inflammation and prevention of coronary thrombosis. The long-term therapy in individuals who develop coronary aneurysms is aimed at preventing myocardial ischemia or infarction.6 The current standard of care for the treatment of children in the U.S. is anti-inflammatory therapy with:
- immunoglobulin (IVIG) in a single 2 g/kg/dose infused over 10–12 hours, accompanied by;
- high-dose aspirin (80–100 mg/kg/day orally in four divided doses).6,15
IVIG administration within 10 days of the onset of fever results in more favorable outcomes. Live virus vaccines should be delayed to 11 months after administration of IVIG. Both aspirin and IVIG have anti-inflammatory effects. This regimen applies to patients without abnormalities on initial echocardiography. High-dose aspirin typically is continued for 48-72 hours after the child becomes afebrile. Thereafter, low-dose aspirin (3-5 mg/kg/day) is prescribed until patient shows no evidence of coronary changes, typically by six to eight weeks after onset of illness. Children with coronary abnormalities should continue aspirin indefinitely.
Approximately 10% of patients are IVIG-resistant and have persistent or recurrent fever for at least 36 hours after completion of the infusion. The current recommendation is to re-treat with IVIG at the same dose. If the patient has fever 36 hours after the second dose of IVIG, this is considered true treatment failure.
Other possible treatments for KD refractory to IVIG include IV methylprednisolone (30 mg/kg over two to three hours daily for three days) or infliximab.16 Even with prompt treatment, 5% of children who have KD develop coronary artery dilation, and 1% develop giant aneurysms.
Back to the Case
Initial laboratory evaluation revealed white blood cell count of 19.0×103 cells/mm3, hemoglobin of 8.9 gm/dL, CRP of 17.9 mg/dL, and ESR of 73 mm/hr. Because of persistent fevers for 48 hours after admission in the absence of another cause to explain the illness, the KD service was consulted. Echocardiography revealed dilatation of the left main (z-score 4.23) and proximal right (z-score 2.59), confirming the diagnosis of KD. Ejection fraction was read as qualitatively normal.