What is the appropriate evaluation and management for a 21‑year‑old healthy male with a painful oral ulcer who is seeking a routine sexually transmitted infection (STI) screen?

Evaluation and Management of Oral Ulcer with STI Screening in a Sexually Active Young Male

This patient requires comprehensive STI testing including oral swabs for gonorrhea and chlamydia, blood tests for syphilis and HIV, and consideration of oral manifestations of sexually transmitted infections, particularly primary syphilis and HSV.

Immediate Diagnostic Approach

Oral Ulcer Evaluation

• Obtain oral swabs from the ulcer site for gonorrhea and chlamydia culture, as the CDC recommends throat cultures for gonorrhea in sexual assault victims and sexually active individuals with oral lesions 1
• Examine ulcer morphology carefully: look for fibrinous/necrotic center, well-delimited borders, undermined edges, or a clean base to differentiate between HSV, syphilis, and other causes 2
• Assess for lymphadenopathy: painful, enlarged cervical or submandibular nodes suggest HSV or syphilis, whereas tender unilateral nodes may indicate other bacterial infections 2

Mandatory Serologic Testing

• Syphilis serology (nontreponemal test: RPR or VDRL) is mandatory for all patients presenting with ulcers in the context of sexual activity, though sensitivity in primary syphilis is only 62-78% 3
• HIV screening is strongly recommended at initial presentation and must be repeated at 3 months if initially negative, as oral ulcers can facilitate HIV transmission 2, 3
• Repeat syphilis testing at 3 months if initial serology is negative, as serologic tests become reliably positive by 4-6 weeks after infection 3

Comprehensive STI Screening Panel

Genital Testing (Even Without Symptoms)

• Urethral swab or first-void urine for nucleic acid amplification testing (NAAT) for N. gonorrhoeae and C. trachomatis, as most STIs present without symptoms 4, 5
• Urethral Gram stain if any urethral symptoms develop (≥5 polymorphonuclear leukocytes per oil immersion field indicates urethritis) 1

Oral-Specific Testing

• Throat culture for gonorrhea is specifically recommended, as pharyngeal gonorrhea can present with oral ulceration or soreness 1
• HSV culture or PCR from the oral ulcer base if vesicular lesions are present or suspected, as HSV accounts for approximately 49% of all ulcer cases 2, 3

Critical Diagnostic Considerations

Oral Manifestations of STIs

• Primary syphilis can present as an oral chancre (painless ulcer with indurated edges), though the classic painless presentation occurs in only 31% of cases 3
• Oral HSV typically progresses from vesicular lesions to shallow ulcerations that crust and heal spontaneously 2
• Pharyngeal gonorrhea may cause throat soreness and can coexist with genital infection 1

Common Pitfalls to Avoid

• Do not rely on symptom absence: most STIs are asymptomatic, and this patient's lack of genital symptoms does not exclude urethral or rectal infections 4, 5
• Co-infection is common: 3-10% of patients with ulcers harbor multiple pathogens, so a single positive test should not preclude evaluation for additional organisms 2, 3
• At least 25% of ulcers remain without laboratory-confirmed diagnosis despite comprehensive testing, highlighting the importance of empiric treatment when indicated 2, 6

Empiric Treatment Considerations

When to Treat Empirically

• If clinical suspicion for syphilis is high (oral chancre appearance), treat with benzathine penicillin G 2.4 million units IM while awaiting serology 2
• If HSV is suspected (vesicular progression, painful shallow ulcers), initiate acyclovir 400 mg orally five times daily for 10 days within 72 hours of symptom onset 2
• For pharyngeal gonorrhea, treat with ceftriaxone 250 mg IM if culture is positive or clinical suspicion is high 1

Follow-Up Protocol

Short-Term Monitoring

• Clinical reassessment at 3-7 days after therapy initiation to evaluate symptom improvement; oral ulcers should improve subjectively within 3 days and objectively within 7 days of appropriate treatment 2, 6
• Large ulcers may require more than 2 weeks for complete healing even with correct therapy 2, 6

Long-Term Surveillance

• Repeat HIV and syphilis testing at 3 months if initially negative to capture seroconversion 2, 3
• Rescreening at 3 months for gonorrhea and chlamydia is recommended, as patients diagnosed with one STI have a 25.8% risk of acquiring new infections within the year 7
• Most reinfections (66.2%) are asymptomatic, making scheduled rescreening essential rather than symptom-based follow-up 7

Risk Stratification

High-Risk Features Requiring Enhanced Surveillance

• Recent sexual activity places this patient at risk for all common STIs including HSV, syphilis, gonorrhea, and chlamydia 5
• Black patients and those with baseline STI have the highest risk for recurrent infection (adjusted odds ratio 2.5 and 2.4 respectively) 7
• Men who have sex with men require additional rectal screening if applicable 1, 5

Partner Management

• Sexual contacts from the past 60 days should be evaluated and treated empirically for any confirmed STI 1
• Instruct the patient to avoid sexual activity until both he and his partners complete treatment and are asymptomatic 1