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Background: The natural history of atherosclerosis has not clearly been elucidated yet. Some works reported that flogosis plays a role in plaque instability. Why does this inflammatory process start? We investigated the correlation between Chlamydia pneumoniae acute infection and plaque rupture., Methods: We compared blood concentrations of IgM anti-Chlamydia pneumoniae in patients affected by acute myocardial infarction (AMI) and in patients affected by stable angina., Results: Our results showed a minimal statistical difference, with a more positive value in patients with AMI. Subsequently, the group affected by AMI was divided into two subgroups with and without plaque rupture: the subgroup with plaque rupture showed a higher blood concentration of Chlamydia antibodies. This subgroup was also divided into two other subgroups according to blood white cell concentration: the subgroup with normal concentration of white blood cells showed the highest value of Chlamydia antibodies., Conclusions: Chlamydia pneumoniae could play an important role in atherosclerotic plaque instability

Atherosclerosis is an inflammatory process disease that involves the artery wall and that is characterized by the progressive accumulation of lipids. The term arteriosclerosis has been created by Lobstein in 1833. Subsequently, during the 19th century, the contribution of Rokitansky and Virchow was important to elucidate the pathogenesis of arteriosclerosis and the morphologic aspects of the plaque. In the beginning of the 20th century, Aschoff was a leading proponent who regarded the morphologically different intimal lipid deposits of children and adults as early and late stages of one disease and he called them atherosis and atherosclerosis, respectively. The first classification of atherosclerosis was made by the World Health Organization (WHO) in 1958 and it consisted of the following sequence: fatty streak, atheroma, fibrous plaque and complicated lesions. In 1990s, thanks to much more sensitive techniques, the American Heart Association (AHA) proposed a new morphological classification based on eight lesion types designated by Roman numerals which indicate the usual sequence of lesion progression. Finally, Virmani et al. (2000) described a classification with the add of a specific plaque type, not recognized by the AHA classification, called "thin fibrous cap atheroma" which is more likely to rupture. The atherosclerotic process is characterized by typical ultrastructural changes that mainly involve the endothelial and smooth muscle cells. The morphological alterations of the endothelium are associated with dysfunctions leading to a proinflammatory and prothrombotic phenotype. This process seems to be due to turbulent blood flow and low fluid shear stress that normally occurs in particular regions of the vascular tree. Inflammation has a key role in the pathogenesis of atherosclerosis and it is supported by numerous factors such as modified LDL, hypertension, diabetes mellitus, free radicals and, in particular, by infectious agents such as Chlamydia pneumoniae.

Papanicolaou smears from 100 woman with ELISA Chlamydia-positive (42) and negative (58) endocervical smears were examined. Chlamydial endocellular inclusions were found in 3 ELISA positive and 2 negative smears, with an evident low sensitivity (7%) of cytology in the diagnosis of the endocervical infection. Furthermore, by statistical analysis it is clear that a negative test doesn't add anything to the pre-test probability (prevalence) of the infection. On the other hand a positive pap-smear adds a poor information, if compared with immunoenzimathic assay and IF staining. Thus, the Papanicolaou smear can't be considered of diagnostic value for Chlamydial infection. Furthermore, it proves unsuitable even for screening programs on high-risk patients, concerning which the immunoenzymatic assay appears, as previously affirmed, the most suitable effort.