kawasaki disease is an acute , self - limited systemic type of vasculitis that occurs predominantly in young children . after the 1st report by tomisaku kawasaki in japan1 ) , it is now recognized as the leading cause of acquired heart disease in children in developed countries . the etiology of kawasaki disease is still unknown and no single pathognomonic clinical or laboratory finding for the diagnosis has been identified . to establish a diagnosis , we inevitably depend on the diagnostic criteria , which are the typical constellation of signs and symptoms , prepared by the japanese kawasaki disease research committee2 ) or the american heart association ( aha)3 ) . however , pediatricians sometimes encounter febrile children who do not fulfill the diagnostic criteria but have several findings compatible with those of kawasaki disease . in this situation , the diagnosis of incomplete kawasaki disease is a clinical challenge , which can not be avoided by delaying the diagnosis because of the risk of coronary complications pertaining even to the incomplete presentation of the disease4,5 ) . the diagnosis of incomplete kawasaki disease is reviewed in this paper . the phrase " atypical kawasaki disease " was initially used to describe patients with coronary complications who do not fulfill the classical diagnostic criteria6 ) . recently , the term " atypical kawasaki disease " has been used to describe patients with incomplete presentation of the disease , regardless of the presence of coronary complications7,8 ) , and is exchangeable for " incomplete kawasaki disease"2,5 ) . newburger et al.9 ) proposed that " atypical kawasaki disease " should be reserved for patients with complications , e.g. , renal impairment , that are generally not seen in kawasaki disease . the diagnostic criteria established by the aha ( table 1)3 ) are different from the japanese criteria ( table 2)2 ) with regard to fever prolongation ( 5 days ) as a necessary criterion . in the japanese criteria , fever prolongation is just an optional criterion and there is no description of the size of cervical lymph nodes ( table 2 ) . in spite of rarely reported cases of kawasaki disease without fever12 ) , a diagnosis of complete kawasaki disease is not difficult in typical cases without regard to a selected criteria . because of a need for early diagnosis and management and alleviation of fever after early infusion of intravenous immunoglobulin ( ivig ) , the duration of fever was modified in the commentary in both criteria2,3 ) . according to the aha criteria , experienced clinicians who have treated many kawasaki disease patients can establish the diagnosis before day 49 ) , and a duration of fever of less than 5 days , which can be achieved by early ivig treatment , can be considered as a principal symptom according to the japanese criteria2 ) . the reported prevalence of incomplete presentation was 15 to 36.2% among patients with kawasaki disease4,5,7,10,11,13 - 15 ) . children with incomplete presentation were more likely to be at the extremes of the age spectrum as compared to those with complete presentation . the prevalence of incomplete presentation was relatively higher in the younger - aged patients16,17 ) . one study reported that patients with incomplete presentation were younger than patients with complete presentation15 ) . in other reports , there was no difference in the mean / median age between the 2 groups5,10,11 ) . however , relatively more children with incomplete presentation were in the extremes of the age spectrum ( 1 year old , or 5 to 9 years old)4,11 ) . the risk of delayed diagnosis and management in young infants with incomplete presentation has been pointed out in the past18,19 ) . no other demographic features ( including gender ) , except the prevalent age , has been reported to be different between patients with incomplete and complete presentation4,11,15 ) . the presence of classical clinical findings in patients with incomplete presentation is properly less frequent than in patients with complete presentation . the frequently reported findings which less frequently observed in incomplete presentation are cervical lymphadenopathy ( 19 to 38.6% ) and extremity changes ( 21 to 44.3% ) , and this pattern of order of observed frequencies is equal to that noted in patients with complete presentation4,10,11,20 ) . comparison of laboratory findings ( complete blood count , albumin , hepatic transaminase , acute phase reactants ) between these 2 groups also showed no significant differences11,20,21 ) . however , low levels of serum alanine aminotransferase10,11,20 ) , low levels of gamma glutamyl transferase10 ) , low frequency of hyponatremia22 ) , and low frequency of pyuria were reported in children with incomplete presentation20 ) . several authors who had compared clinical characteristics between the 2 forms of kawasaki disease suggested that they are not separate entities but are probably located along a continuous spectrum , placing more weight on demographic and laboratory similarities between the 2 groups8,10,11 ) . on the basis of this suggestion , making the diagnosis of incomplete kawasaki disease in analogy to the findings of complete presentation could be reasonable . contradicting studies reported incomplete presentation of kawasaki disease in children to be associated with higher risk4,5,10,15 ) , similar risk11 ) , or lower risk21 ) of coronary artery abnormalities compared to children with complete presentation . sudo et al.15 ) concluded that the higher incidence of coronary artery lesions in patients with incomplete presentation was firstly due to diagnostic bias because of the use of echocardiography in the diagnostic process , and secondly due to delays in the treatment because of difficulties in making the diagnosis . restricting the diagnosis of incomplete kawasaki disease within children with echocardiographic coronary artery abnormalities will result in above mentioned diagnostic bias . manlhiot et al.11 ) elucidated equal incidences of coronary artery abnormalities between both patient groups using their definition of incomplete presentation of kawasaki disease in which the use of echocardiography is excluded . in children with incomplete kawasaki disease , the time between onset of symptoms and diagnosis has been reported to be longer5,11,15 ) , and they are less likely to receive ivig than children with complete presentation11,15 ) . sudo et al.15 ) performed multivariate analysis to delineate risk factors of coronary artery lesions and showed that late ivig treatment ( 7 days of illness ) was a significant risk factor of coronary artery lesions in both patient groups . the presence of coronary artery abnormalities has been used as criterion for the diagnosis of incomplete kawasaki disease2,6 ) . according to the japanese criteria , this criterion can only be used in cases with 4 principal symptoms2 ) . first of all , pediatric clinicians sometimes encounter cases in which kawasaki disease is suspected with less than 4 principal symptoms . in the diagnostic criteria for incomplete presentation prepared by the aha , a diagnosis of incomplete kawasaki disease is possible in cases with fever and 2 principal features ( according to japanese criteria , 3 principal symptoms)9 ) . secondly , the presence of coronary artery abnormalities is in itself an unfavorable outcome of the disease . the duration of fever has been confirmed as an important risk factor of coronary artery abnormalities23 - 25 ) . therefore , it may induce a delay of management to postpone diagnosis of incomplete presentation until confirming of coronary artery abnormality . one study in which the definition of incomplete kawasaki disease included coronary involvement showed higher coronary complications in the group of infants younger than 6 months of age which had more cases of incomplete disease16 ) . finally , the japanese ministry of health criteria ( table 3b)26 ) , which have been used as a standard for the diagnosis of coronary complications , are too restrictive . de zorzi et al.27 ) showed that the z score of coronary arteries ( adjusted for body surface area ) was more than 2 in 27% of children with kawasaki disease whose coronary artery diameters were classified as normal according to the japanese ministry of health criteria . the increase of body surface area - adjusted z score of the coronary diameter was adopted as a standard of coronary artery dilatation in the diagnostic criteria of incomplete kawasaki disease by the aha9 ) . sudo et al.15 ) collected data from a total of 23,263 cases with kawasaki disease in the nationwide survey of japan from 2007 through 2008 . incomplete kawasaki disease was defined as the presence of 4 principal symptoms of the japanese criteria , regardless of whether the patient had coronary artery abnormalities15 ) . the prevalence of coronary artery abnormalities was 13.1% in cases with incomplete presentation15 ) . due to the nature of that study , it was impossible to standardize the diagnostic criteria across all centers ; therefore , the clinicians ' judgment and local policies may have played a significant role in those cases with few classical diagnostic criteria15 ) . in the incomplete presentation group , 271 children ( 1.2% ) with only 1 or 2 principal symptoms were included15 ) . currently , a diagnosis of incomplete kawasaki disease might be made in cases with fewer classical diagnostic criteria and with several compatible clinical , laboratory , or echocardiographic findings , excluding those of other febrile illnesses . according to the diagnostic criteria of incomplete kawasaki disease established by the aha , children 6 months of age with incomplete presentation might have unexplained fever for 5 days associated with 2 or 3 of the principal clinical features ( compatible with 3 or 4 principal symptoms of the japanese criteria ) in the acute phase9 ) . the aha recommended a diagnostic algorithm of incomplete kawasaki disease which comprises of 6 supplemental laboratory and echocardiographic criteria ( table 3)9 ) . more than 3 laboratory criteria support the diagnosis of incomplete kawasaki disease ( table 3a ) . for judging an anemia and an abnormal level of alanine aminotransferase echocardiogram is considered diagnostically positive if any of the following 3 conditions are met : z score of the left anterior descending or right coronary arteries 2.5 , coronary arteries meet the japanese ministry of health criteria for aneurysms26 ) , or 3 other suggestive features exist ( table 3b ) . several echocardiographic criteria , except the z score of coronary arteries , are qualitative parameters . recently , quantitation of the perivascular brightness of coronary arteries was performed in children with kawasaki disease , but its diagnostic validity could not be demonstrated28 ) . decreased myocardial contractility caused by myocarditis , which is histologically universal , is common during the acute phase of kawasaki disease29,30 ) . thus , evaluation of myocardial contractility is an important step in the initial diagnosis of kawasaki disease and was adopted as an echocardiographic criterion . left ventricular dimensions / volumes , shortening fraction or ejection fraction via the m - mode in parasternal view or via a 2-dimensional examination in apical view are recommended parameters , because they are readily measurable and adequate for routine follow - up9 ) . left ventricular myocardial deformation was analyzed during the acute phase of kawasaki disease in 1 study31 ) , but the systolic strain rate of the myocardium was not superior to other conventional echocardiographic methods for detecting decreased myocardial contractility . no convincing quantitative threshold values have been proposed for the decision of abnormal pericardial effusion or mitral regurgitation during the acute phase of kawasaki disease . newburger et al.9 ) acknowledged the diagnostic criteria for incomplete kawasaki disease prepared by them to be only an informed opinion of a committee of experts ( evidence level c ) . yellen et al.20 ) tested the performance of the diagnostic criteria established by the aha and reported an applicability of 97% . the validity of the diagnostic criteria of incomplete kawasaki disease established by the aha should be thoroughly tested in the immediate future because such a systematized guideline is very much needed in pediatric clinical practice . additional diagnostically helpful findings are inflammation at the bacille calmette - gurin inoculation site32 ) , anterior uveitis10,18 ) , elevated levels of brain natriuretic peptide ( bnp)33 - 36 ) and n - terminal pro - bnp37 ) , hyponatremia22 ) , elevation of the left ventricular mass38 ) , and diastolic dysfunction of the left ventricle35,39 ) . the diagnostic validities of these clinical , laboratory , and echocardiographic findings should also be tested in the future . currently , the diagnosis of incomplete kawasaki disease might be made in cases with fewer classical diagnostic criteria and with several compatible clinical , laboratory , or echocardiographic findings , excluding those of other febrile illnesses . in addition , the validity of the diagnostic criteria of incomplete kawasaki disease prepared by the aha should be tested in the future .
several authors suggested that the clinical characteristics of incomplete presentation of kawasaki disease are similar to those of complete presentation and that the 2 forms of presentation are not separate entities . 
 based on this suggestion , a diagnosis of incomplete kawasaki disease in analogy to the findings of complete presentation is reasonable . 
 currently , the diagnosis of incomplete kawasaki disease might be made in cases with fewer classical diagnostic criteria and with several compatible clinical , laboratory or echocardiographic findings on the exclusion of other febrile illness . 
 definition of incomplete presentation in which coronary artery abnormalities are included as a necessary condition , is restrictive and specific . 
 the validity of the diagnostic criteria of incomplete presentation by the american heart association should be thoroughly tested in the immediate future .