Anogenital chlamydial infection is caused by the bacterium Chlamydia trachomatis and is a very common sexually transmitted infection (STI). The prevalence of this infection is greatest in adolescents and young adults.

Patients are infected during sexual intercourse, when the urethra or rectum is inoculated with the organism. Pharyngeal infection is also possible.

The incubation period is 7-14 days. Many infected patients are asymptomatic. Symptoms can vary depending on the location of the infection. Patients with urethritis may complain of dysuria or urethral pruritus. Epididymitis presents with epididymal pain (usually unilateral) and sometimes fever. Proctitis presents with rectal pain and discharge (sometimes bloody). Lymphogranuloma venereum (LGV) is a disease caused by certain serovars of C trachomatis. Symptoms include severe proctocolitis with rectal discharge, pain, and fever. Tender inguinal lymphadenopathy may also be seen (the "groove sign").

Coinfection with other STIs, including gonorrhea, is common. Some patients may develop reactive arthritis.

Although evidence is insufficient to recommend routine screening for C trachomatis among sexually active young men because of certain factors (ie, feasibility, efficacy, and cost-effectiveness), screening of sexually active young men should be considered in clinical settings with a high prevalence of chlamydia (eg, adolescent clinics, correctional facilities, or STI specialty clinics) or for populations with a high burden of infection (eg, men who have sex with men [MSM]).