Atypical Kawasaki disease—a clinical challenge

Excerpt

For the modern day pediatrician, the early recognition of clinical signs, a timely diagnosis and early initiation of treatment of Kawasaki Disease (KD), is a key clinical skill. It is the second most common form of systemic childhood vasculitis and the most common cause of acquired heart disease in children due to the potential for coronary artery aneurysm, myocarditis, and pericardial effusion [3, 12]. The exact etiology of KD remains elusive and hence no single diagnostic test is available to categorically confirm KD and aid in the diagnostic decision making process. There is variation in the incidence of pediatric KD dependent on race of between 9.1 and 32.5/100,000 in USA and 216.9/100,000 in Japan [2, 7]. There is a slight male preponderance of around 1.5:1 and a seasonal variation with higher numbers seen in the winter and spring. The diagnosis of KD relies on the early identification of the key clinical components of prolonged fever and presence of the following clinical signs: bilateral non-exudative conjunctivitis, erythema of the lips and oral mucosa, changes in the extremities, rash, and cervical lymphadenopathy. Additional helpful but non diagnostic clinical signs such as Bacille Calmette–Guérin inoculation site reactivation may support the diagnosis [10]. Certainly supplementary laboratory markers play an important role; elevation of acute phase reactants, C reactive protein and erythrocyte sedimentation rate along with low serum albumin levels are important correlates to the early acute phase along with thrombocytosis present later in the disease process. Noninvasive imaging with echocardiography which is not used in the diagnosis of the complete form of the disease may play a more important role in the incomplete presentation. The differential diagnosis list may be long especially in patient groups outside the typical age range with infective, rheumatologic, and hypersensitivity reactions all among the possibilities. There is a consensus that early treatment with intravenous immunoglobulin (IVIG) and anti-inflammatory doses of aspirin in the acute phase of the disease reduces the risk of coronary aneurysm development and is important for the prevention of long-term morbidity associated with the disease [8]. It is a logical assumption that early diagnosis leads to a reduced time delay before appropriate treatment with IVIG can be instigated. The difficulty and possible uncertainties in diagnosis occur when not all of the classical signs are present and the physician is faced with an incomplete or atypical presentation of the disease. Many large epidemiological studies have estimated that around 20% of all cases fall into the incomplete presentation group with four or less typical features [7]. It has been suggested that this patient group is at greater risk of developing the more serious cardiac sequelae of KD, most notably coronary artery aneurysm (CAA); this higher risk has been attributed to the delay in commencement of therapeutic treatment options in a timely fashion. Guidelines published by the American Heart Association in 2004 [8] and the Kawasaki Disease Research Committee in 2005 [1] form the framework on which diagnosis and treatment algorithms in USA and Japan have been based. These include suggestions on how to incorporate those patients who presented with an incomplete clinical picture into the KD care pathway …