What could be causing a vaginal lesion with discomfort to touch, slight itch, and white milky discharge in a long-term monogamous relationship?

Vaginal Lesion with White Discharge: Most Likely Diagnosis and Management

This presentation most likely represents vulvovaginal candidiasis (yeast infection), which accounts for 20-25% of vaginitis cases and classically presents with vulvar discomfort, itching, and thick white discharge. 1, 2

Primary Diagnostic Considerations

The combination of a tender lesion, slight itch, and white milky discharge in a monogamous relationship strongly suggests:

Most Likely: Vulvovaginal Candidiasis

• Candidiasis typically presents with thick white "curdled" discharge, vulvar pruritus, hyperemic vagina, and erythematous/excoriated vulva—matching this clinical picture. 3
• Approximately 75% of women experience at least one episode during their lifetime, making this the most common explanation. 4
• The vaginal pH remains normal (3.8-4.2) in uncomplicated candidiasis, distinguishing it from other causes. 3
• Microscopic examination reveals hyphae or budding yeast in 50-70% of cases. 3

Alternative Consideration: Bacterial Vaginosis

• BV is the most prevalent cause of vaginal discharge overall (40-50% of identified cases), but typically presents with homogeneous white discharge that adheres to vaginal walls rather than a discrete lesion. 5, 2
• The vaginal pH is elevated (>4.5) in BV, and discharge has a characteristic fishy odor. 1
• Standard clinical testing misses 20-30% of BV cases, so this remains possible even if initial testing is negative. 5, 6

Less Likely but Important to Exclude: Herpes Simplex Virus

• HSV is the most common cause of genital ulcers in the United States and can present with painful lesions. 1
• However, HSV typically causes vesicles that rupture into painful ulcers rather than lesions with white discharge. 1
• Monogamous relationship status does not exclude HSV, as the virus can remain dormant for years. 1

Diagnostic Algorithm

Step 1: Measure Vaginal pH

• Use narrow-range pH paper directly on vaginal secretions. 5
• pH ≤4.5 suggests candidiasis. 5
• pH >4.5 suggests BV or trichomoniasis. 1, 5

Step 2: Perform Wet Mount Microscopy

• Prepare saline wet mount to look for clue cells (BV) and motile trichomonads. 5
• Prepare KOH wet mount to assess for fishy odor (whiff test) and look for yeast or pseudohyphae. 5
• The whiff test is positive in BV or trichomoniasis but negative in candidiasis. 1

Step 3: Examine the Lesion Characteristics

• If the lesion is a vesicle, pustule, or ulcer, obtain viral culture for HSV and serologic tests for syphilis. 1
• Papules or warts suggest human papillomavirus. 1

Treatment Recommendations

For Confirmed Candidiasis (Most Likely)

Treat with fluconazole 150 mg orally as a single dose, which has a 55% therapeutic cure rate and is the most convenient option. 5, 4

Alternative topical regimens include:

• Miconazole 2% cream 5g intravaginally for 7 days. 1
• Clotrimazole 1% cream 5g intravaginally for 7-14 days. 1
• Multi-day regimens (3- and 7-day) are preferred for severe or complicated cases. 1

For Confirmed Bacterial Vaginosis

Treat with metronidazole 500 mg orally twice daily for 7 days, which has a 95% cure rate. 1, 6

• The 7-day regimen is superior to single-dose metronidazole 2g (84% cure rate). 6
• Patients should avoid alcohol during treatment and for 24 hours after. 1

For Confirmed HSV

• Initiate antiviral therapy if vesicular or ulcerative lesions are present. 1

Critical Pitfalls to Avoid

• Do not assume negative initial STD testing rules out BV—retesting with Gram stain is recommended when symptoms persist, as standard testing misses 20-30% of cases. 5, 6
• Do not treat asymptomatic patients with incidental bacterial findings and no clue cells, as this leads to inappropriate antibiotic use. 5, 6
• Recognize that approximately 15% of Candida albicans organisms are resistant to clotrimazole and miconazole—if treatment fails, consider fluconazole or culture to identify non-albicans species. 3
• BV has a 50-80% recurrence rate within one year, which may explain persistent symptoms despite previous treatment. 6
• Partner treatment is NOT indicated for candidiasis or BV, only for sexually transmitted infections like trichomoniasis. 7

When to Reconsider the Diagnosis

If symptoms persist after appropriate treatment, laboratory testing fails to identify the cause in a substantial minority of women—consider non-infectious causes including atrophic vaginitis, irritant/allergic vaginitis, or desquamative inflammatory vaginitis. 5, 8