Kawasaki Disease ETIOLOGY Kawasaki disease (KD) is a vasculitis of unknown etiology that is characterized by multisystem involvement and inflammation of small to medium-sized arteries with resulting aneurysm formation. Although many causes of KD have been hypothesized, no single underlying etiology has been ascertained. EPIDEMIOLOGY KD is a common vasculitis of childhood that has been described in variable frequency in all parts of the world; the highest frequency is in Japan. Although KD can affect children of all races, it is more common in children of Asian descent. The incidence in the United States is approximately 6 per 100,000 children who are younger than 5 years of age. KD most commonly occurs in children younger than 5 years of age, with a peak between 2 to 3 years, and is rare in children older than 7 years. A seasonal variability has been described with a peak between February and May, but the disease occurs throughout the year. CLINICAL MANIFESTATIONS The clinical course of KD can be divided into three phases, each with its own unique manifestations. Aneurysmal involvement of the coronary arteries is the most important manifestation of KD. Acute Phase The acute phase of KD, which lasts 1 to 2 weeks, is marked by sudden onset of a high, hectic fever (≥40 °C) without an apparent source. The onset of fever is followed by conjunctival erythema; mucosal changes, including dry, cracked lips and a strawberry tongue; cervical lymphadenopathy; and swelling of the hands and feet (Fig. 88-1). Conjunctivitis is bilateral, bulbar, and nonsuppurative. Cervical lymphadenopathy is found in 70% of children and should be greater than 1.5 cm in diameter for the purposes of diagnosis. A rash, which can vary in appearance, occurs in 80% of children with KD and may be particularly accentuated in the inguinal area and on the chest. Extreme irritability is prominent, especially in infants. Abdominal pain and hydrops of the gallbladder, pleocytosis, and arthritis, particularly of medium-sized to large joints, may occur. Carditis in the acute phase may be manifested by tachycardia, shortness of breath, or overt congestive heart failure. Giant coronary artery aneurysms, which are rare but occur most commonly in very young children, can appear during this phase. LABORATORY AND IMAGING STUDIES It is particularly important to exclude other causes of fever, notably infection. It is appropriate to obtain blood and urine cultures and to perform a chest x-ray. In the acute phase, inflammatory parameters are elevated, including white blood cell count, platelet count, C-reactive protein, and the ESR, which can be profoundly elevated (often >80 mm/hr). A lumbar puncture, if performed to exclude infection, may reveal pleocytosis. Tests of hepatobiliary function may be abnormal. Greatly elevated platelet counts develop during the subacute phase. The development of coronary artery aneurysms is monitored by performing two-dimensional echocardiograms, usually during the acute phase, at 2 to 3 weeks, and at 6 to 8 weeks. More frequent echocardiograms and, potentially, coronary angiography are indicated for patients who develop coronary artery abnormalities. DIFFERENTIAL DIAGNOSIS The diagnosis of KD is based on the presence of fever for more than 5 days without an identifiable source and the presence of four of five other clinical criteria (Table 88-1). The diagnosis of incomplete (atypical) KD, which occurs more commonly in infants, is made when fever is present for at least 5 days even if only two or three clinical criteria are present. The diagnosis of KD should be considered in infants younger than 6 months of age with fever for at least 7 days even if no other criteria are present. Because many of the manifestations of KD are found in other illnesses, many diagnoses must be considered and excluded before the diagnosis of KD can be established (Table 88-2). TREATMENT Table 88-1. Criteria for Diagnosis of Kawasaki Disease Fever of ≥5 days duration associated with at least four* of the following five changes: Bilateral nonsuppurative conjunctivitis One or more changes of the mucous membranes of the upper respiratory tract, including pharyngeal injection, dry fissured lips, injected lips, and strawberry tongue One or more changes of the extremities, including peripheral erythema, peripheral edema, periungual desquamation, and generalized desquamation Polymorphous rash, primarily truncal Cervical lymphadenopathy >1.5 cm in diameter Disease cannot be explained by some other known disease process *A diagnosis of Kawasaki disease can be made if fever and only three changes are present in conjunction with coronary artery disease documented by two-dimensional echocardiography or coronary angiography. Table 88-2. Differential Diagnosis of Kawasaki Disease INFECTIOUS Scarlet fever Epstein-Barr virus Adenovirus Meningococcemia Measles Rubella Roseola infantum Staphylococcal toxic shock syndrome Scalded skin syndrome Toxoplasmosis Leptospirosis Rocky Mountain spotted fever INFLAMMATORY Juvenile rheumatoid arthritis (systemic onset) Polyarteritis nodosa Behçet syndrome HYPERSENSITIVITY Drug reaction Stevens-Johnson syndrome (erythema multiforme) Intravenous immunoglobulin (IVIG) is the mainstay of therapy for KD, although the mechanism of action is unknown. A single dose of IVIG (2 g/kg over 12 hours) results in rapid defervescence and resolution of clinical illness in most patients and, more importantly, reduces the incidence of coronary artery aneurysms. Aspirin is initially given in anti-inflammatory doses (80 to 100 mg/kg/day divided every 6 hours) in the acute phase. Some experts recommend continuing high-dose aspirin until the 14th day and at least 3 days without fever; others recommend only until 48 hours without fever. Aspirin in antithrombotic doses (3 to 5 mg/kg/day as a single dose) is administered through the subacute and convalescent phases, usually for 6 to 8 weeks, until follow-up echocardiography documents the absence of coronary artery aneurysms. Approximately 3% to 5% of children with KD initially fail to respond satisfactorily to IVIG therapy. Most of these patients respond to retreatment with IVIG (2 g/kg over 12 hours), but an alternative preparation of IVIG may be required. Corticosteroids or infliximab are rarely used in KD, as opposed to other vasculitides, but may have a role during the acute phase if active carditis is apparent or for children with persistent fever after two doses of IVIG. COMPLICATIONS Most cases resolve without sequelae. Myocardial infarction has been documented, most likely caused by stenosis of a coronary artery at the site of an aneurysm. Coronary artery aneurysms found on autopsy in older children following sudden cardiac death may have been due to past KD. Other complications are listed in Table 88-3. PROGNOSIS IVIG reduces the prevalence of coronary artery disease from 20% to 25% in children treated with aspirin alone to 2% to 4% in children treated with IVIG and aspirin. Other than the risk of persistent coronary artery aneurysms, KD has an excellent prognosis. Table 88-3. Complications of Kawasaki Disease Coronary artery thrombosis Peripheral artery aneurysm Coronary artery aneurysms Myocardial infarction Myopericarditis Congestive heart failure Hydrops of gallbladder Aseptic meningitis Irritability Arthritis Sterile pyuria (urethritis) Thrombocytosis (late) Diarrhea Pancreatitis Peripheral gangrene
Posted on: Fri, 14 Mar 2014 13:54:04 +0000
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