An association between symptomatic carotid stenosis and recent infection wi
th Chlamydia pneumoniae is reported. Thirty-five patients (20 symptomatic a
nd 15 asymptomatic) with carotid stenosis of 70% to 90% underwent carotid e
ndarterectomy. Endarterectomy was performed without patch and shunt; the av
erage occlusion time of the internal carotid artery was 14 +/- 3 min. The a
theromatic plaque and a portion of the thyroid artery were examined with po
lymerase chain reaction and peripheral vein blood was obtained for serologi
c detection of systematic infection, and IgG and IgM antibodies to C. pneum
oniae by enzyme-linked immunosorbent assay.
Twenty of 35 patients (57.1%) had increased titers of IgG antibodies to C p
neumoniae. Eight patients revealed IgG plus IgM antibodies; two of the eigh
t had IgG, IgM, and positive findings on polymerase chain reaction. No C pn
eumoniae was detected on the thyroid arteries. Sixty-five percent (13/20) o
f the patients with increased IgG antibodies to C pneumoniae, 87.5% (7/8) w
ith IgG + IgM, and 100% with IgG + IgM + positive polymerase chain reaction
were symptomatic. Plaque morphology in association with symptoms did not r
eveal a significant correlation between soft plaques and symptoms, whereas
the majority of the symptomatic patients had plaques of type III-V. Patient
s having recent contamination and positive polymerase chain reaction had a
significant relationship between C pneumoniae infection and symptomatic car
otid disease. This supports the hypothesis that C pneumoniae infection can
produce a kind of instability of the carotid plaque. The results of this st
udy demonstrate that patients with advanced atherosclerotic carotid disease
have an increased incidence of C pneumoniae infection. Recent infection co
uld be responsible for instability of the carotid plaque, causing cerebral
ischemic episodes.