Failure to demonstrate Chlamydia pneumoniae in cardiovascular tissue from children with Kawasaki disease

Infection and vasculitis

Vasculitis may be associated with infection, immunization or anti-microbial drugs. Infections are responsible for a number of different types of vasculitis. Conversely, patients with vasculitis may develop infections, which sometimes mimic relapse. The aim of this review is to summarize the various aspects of the inter-relationship between vasculitis and infection, and the physiopathological mechanisms involved, in light of our current knowledge from animal models. Currently, a causal relationship between infection and vasculitis has only been established in a few instances and many mechanisms remain hypothetical. This inter-relationship is further assessed from the point of view of clinical presentation and therapeutic options, based on case reports and prospective observational data.

Kawasaki disease: what is the epidemiology telling us about the etiology?

Kawasaki disease (KD) is an important and common inflammatory vasculitis of early childhood with a striking predilection for the coronary arteries. It is the predominant cause of paediatric acquired heart disease in developed countries. Despite 40 years of research, the aetiology of KD remains unknown and consequently there is no diagnostic test and treatment is non-specific and sub-optimal. The consensus is that KD is due to one or more widely distributed infectious agent(s), which evoke an abnormal immunological response in genetically susceptible individuals. The epidemiology of KD has been extensively investigated in many populations and provides much of the supporting evidence for the consensus regarding etiology. These epidemiological data are reviewed here, in the context of the etiopathogenesis. It is suggested that these data provide additional clues regarding the cause of KD and may account for some of the continuing controversies in the field.

Elevated levels of matrix metalloproteinase 9 and tissue inhibitor of metalloproteinase 1 during the acute phase of Kawasaki disease

Kawasaki disease (KD) is an acute, self-limiting, multisystem vasculitis of unknown etiology affecting infants and young children. Unless treated promptly with high-dose intravenous gamma globulin and aspirin, patients frequently develop coronary aneurysms. Previously, matrix metalloproteinase 9 (MMP-9), which is secreted complexed to tissue inhibitor of metalloproteinase 1 (TIMP-1), has been implicated in abdominal aortic aneurysm formation. Since the clinical and pathological features of KD include inflammation and weakening of blood vessels, we analyzed acute- and convalescent-phase paired plasma or serum samples from 31 KD patients, 7 patients who did not completely meet the criteria for KD, and 26 non-KD controls (9 febrile and 17 afebrile patients) for pro-MMP-9 (92 kDa) enzyme activity by gelatin zymography and for active MMP-9 (83 kDa), pro-MMP-9, and TIMP-1 protein levels by enzyme-linked immunosorbent assay. Statistical analysis was performed by using Student t tests, linear regression, and the Wilcoxon rank-sum test. Markedly elevated pro-MMP-9 enzymatic activity, pro-MMP-9 protein levels, and TIMP-1 protein levels were found during the acute phase of illness in patients with clinically established KD and in patients who were suspected of having KD but did not meet all of the criteria. There was no significant difference in active MMP-9 levels. Furthermore, pro-MMP-9 and TIMP-1 protein levels were significantly elevated among KD patients, compared to those of febrile and afebrile non-KD controls. The significantly elevated pro-MMP-9 enzyme and protein levels during the acute phase of KD may reflect vascular remodeling or an inflammatory response to a microbial agent, suggesting a pathophysiological role for MMP-9 in coronary aneurysm formation.