Presentation after 10 days of illness increases the risk of coronary artery involvement.

Risk factors for coronary artery involvement

Box 2 Clinical investigations The following tests are often abnormal during the first 7-10 days and may support the diagnosis of Kawasaki disease, although in isolation these tests lack adequate sensitivity and specificity. Some parameters have age dependent normal ranges1 13 14 w11 Haematology: Raised white blood cell count with neutrophilia (at least 50% of cases), progressive anaemia (usually normochromic and normocytic), increasing platelet count (peaking in the second or third week of illness and therefore not useful diagnostically) Urine analysis: The urinary sediment may contain increased numbers of white blood cells without bacteruria Acute phase reactants: Raised C reactive protein (>35 mg/l in 80% of cases), erythrocyte sedimentation rate (>60 mm/h in 60% of cases). The erythrocyte sedimentation rate may be even higher after intravenous immunoglobulins Blood chemistry: Low serum sodium, low serum protein and albumin, raised liver enzymes (specifically alanine aminotranferase), and abnormal lipid profile (which may be exacerbated by intravenous immunoglobulin) Cerebrospinal fluid: Pleocytosis, usually lymphocytic with normal protein and glucose Electrocardiography: Other than tachycardia, findings include decreased QRS voltages, flattened T waves, and prolonged rate corrected QT intervals. These findings are almost always reversible. Arrythmias including heart block may occur. In untreated large coronary artery aneurysms, electrocardiography may show signs of myocardial infarction as a result of coronary thrombosis Echocardiography: This may show decreased left ventricular function, mitral regurgitation, and pericardial effusion. Coronary artery dilatation begins an average of 9-10 days after onset of fever and occurs in 30-50% of cases