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Chlamydia pneumoniae infection as a potential etiologic factor in atherosclerosis

Jeffrey L Anderson, MD
Section Editor
Christopher P Cannon, MD
Deputy Editor
Gordon M Saperia, MD, FACC


Atherosclerosis is a highly prevalent disease, responsible for the greatest morbidity and mortality in Western civilization. Many risk factors for the development of atherosclerosis, manifest as coronary heart disease (CHD) and myocardial infarction (MI), have been identified. These include hyperlipidemia, hypertension, smoking, and diabetes mellitus. (See "Overview of the risk equivalents and established risk factors for cardiovascular disease".) However, much of the attributable risk remains unexplained.

Inflammation plays a central role in the pathogenesis of atherosclerosis, suggesting the possible involvement of infectious agents. Among the organisms that have been implicated are cytomegalovirus, Helicobacter pylori, and Chlamydia (also referred to as Chlamydophila) pneumoniae (figure 1). Strong associations have been noted between C. pneumoniae and atherosclerosis, which provided the rationale for antibiotic therapy directed against C. pneumoniae.

The data regarding C. pneumoniae infection will be reviewed here. As will be seen, the data fail to support a benefit from anti-C. pneumoniae therapy.


C. pneumoniae is a recently recognized and characterized human pathogen; isolates from respiratory infections were first reported in 1986 [1]. Subsequent epidemiologic studies found it to be the cause of 5 to 10 percent of respiratory infections in adults and children, making it the third most common etiologic agent [2]. (See "Pneumonia caused by Chlamydia pneumoniae in adults".) Antibody prevalence studies suggest that over 50 percent of adults worldwide have been exposed to C. pneumoniae [3].


C. pneumoniae is transported from the respiratory tract to the vascular wall by circulating monocytes, and may persist within the monocytes for at least 10 days without cellular lysis [4]. Case reports have documented the ability of C. pneumoniae to cause vasculitis and myocarditis (figure 1). It also has been noted to cause accelerated atherosclerosis in animal models, possibly by inducing procoagulant protein (plasminogen activator inhibitor-1 and tissue factor) and proinflammatory cytokine (interleukin-6) expression [5]. More direct evidence of an association with atherosclerotic disease has been derived from serologic and pathologic studies.


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Literature review current through: Jun 2017. | This topic last updated: Sep 28, 2015.
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