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Inflammation / parasites

Chlamydia trachomatis

Reviewer: Farnaz Hasteh, M.D., UCSD Medical Center (see Reviewers page)
Revised: 11 June 2011, last major update October 2010
Copyright: (c) 2006-2010, PathologyOutlines.com, Inc.


Chlamydia trachomatis is the most common sexually transmitted bacterial infection in the U.S.


● Transmitted by sexual intercourse and during delivery to babies
● Risk factors include sexually active young women, OCP use, pregnancy


● Immunotypes A-C cause trachoma (chronic conjunctivitis endemic in Africa and Asia)
● Immunotypes D-K cause genital tract infections (eMedicine)
● Immunotypes L1-L3 cause lymphogranuloma venereum (associated with genital ulcer disease in tropical countries)


● Caused by an obligate intracellular parasite with elementary bodies (infectious but incapable of cell division) and reticulate bodies (multiply within cytoplasm, but not infectious until they transfer back into elementary bodies)

Clinical features

● Infection is usually not associated with symptoms (Sex Health 2004; 1:115)
● Symptoms, present in 1/3, include mucopurulent cervicitis with yellow exudate
● PID and infertility are late complications
● Also leading cause of pneumonia and pinkeye in neonates
● Diagnosis is based on molecular tests (PCR or ligase chain reaction)
● Not associated with cervical cancer (Diagn Cytopathol 2007;35:198)


● Doxycycline (eMedicine)
● Patient and all sex partners should be treated

Micro description

● Associated with follicular cervicitis

Cytology description

● Involvement of endocervical cells or metaplastic cells but not mature squamous cells
● Granular cytoplasm with multiple intracytoplasmic inclusions with central small coccoid bodies
● Targetoid inclusion within large intracytoplasmic vacuole
● “Nebular bodies” are more specific, but are difficult to differentiate from intracytoplasmic mucin vacuoles (Diagn Cytopathol 1991;7:252)
● Nuclear enlargement, hyperchromasia or multinucleation
● Marked acute inflammation is common

Cytology images

Various images

Thin Prep

Molecular/cytogenetics description

● Residual liquid based pap (LBP) test can be submitted for both microbiological testing (Chlamydia and Neisseria), as well as DNA testing for HPV (Diagn Cytopathol 2005;33:177)

End of Cervix-cytology > Inflammation / parasites > Chlamydia trachomatis

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