INFECTION CAUSED BY C. TRACHOMATIS
Three of fifteen known strains of C.
trachomatis described as serovars L1, L2, and L3 are responsible for LGV. While the strains of Chlamydia that cause urethritis appear to infect only squamocolumnar cells, LGV strains are more invasive and capable of replication in macrophages.
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DIFFERENTIAL DIAGNOSIS
β’ Inguinal adenitis - chancroid, granuloma inguinale (Donovanosis), genital herpes or syphilis. In the USA, one or more of these is much more likely than LGV, especially if the diagnosed adenitis is associated with a
prominent genital ulceration. Other causes of inguinal adenitis include cat-scratch disease, lymphoma, HIV, reactive adenopathy due to skin lesions on the lower extremities. Less common: lymphoproliferative buboes.
β’ Buboes or suppurative adenitis - chancroid, donovanosis, plague, tularemia, sporotrichosis, actinomycosis or tuberculosis
β’ Retroperitoneal adenitis - may present as lower abdominal pain with subsequent extensive differential diagnosis
β’ Proctitis - gonococcal and non-LGV chlamydial proctitis as well as antibiotic-induced and infectious proctitis. Also inflammatory bowel disease.
β’ Lymphatic obstruction - consider schistosomiasis or malignancy
OTHER TESTS :
* URETHRAL DISCHARGE FOR CULTURE
* DIRECT MICROSCOPIC EXAM OF GIEMSA STAINED CELL SCRAPINGS FOR INCLUSION BODIES HAS LOW SENSTIVITY
* DIRECT FLUORESCENT ANTIBODY STAINING - MORE SENSITIVE
* CELL CULTURE METHODS - LOW SENSTIVITY 60 - 80 %
* DIRECT IMMUNOFLUORESCENT ANTIBODY SLIDE TEST - 70 - 85 %
* ELISA TEST - SENSTIVITY 80 - 90%
* NUCLEIC ACID AMPLIFICATION TESTING OF FIRST-VOID URINE
* PCR TEST - MOST SENSITIVE
* Antibody levels to L1, L2, and L3 serovars of C. trachomatis can also be measured with complement fi xation although cross-reactivity with other Chlamydial organisms is possible.
β’ A fourfold rise in MIF titer to LGV antigen or a complement fixation titer above 1:64, with the proper clinical scenario, is probably LGV. Complement levels above 1:128 confirm the LGV diagnosis. These levels are reached early in the disease. Acute and convalescent titers usually do not vary much at six weeks.
β’ MIF titers are more sensitive and specifi c than the complement fixation test, however they are only used in specialized research labs and are not routinely available