What is the most likely diagnosis in a 27-year-old woman with nocturnal vulvar itching, foul‑smelling frothy yellow‑green vaginal discharge, erythematous edematous vulva, an inflamed friable cervix, and a wet preparation showing flagellated protozoa?

Diagnosis: Trichomoniasis

The most likely diagnosis is C. Trichomoniasis, based on the pathognomonic finding of flagellated protozoa on wet preparation combined with the classic clinical presentation of frothy yellow-green discharge, vulvar erythema, and cervical inflammation. 1

Diagnostic Reasoning

Definitive Microscopic Finding

• The presence of flagellated protozoa on wet mount is diagnostic for Trichomonas vaginalis infection, eliminating all other differential diagnoses 1, 2
• This motile, flagellated organism is the etiologic agent of trichomoniasis and cannot be confused with other pathogens when visualized 3

Classic Clinical Presentation Confirms Trichomoniasis

• Frothy, yellow-green vaginal discharge is the hallmark presentation of trichomoniasis, as defined by CDC guidelines 1
• The inflamed, friable cervix described in this case represents "strawberry cervix" (colpitis macularis), which has an odds ratio of 241 for trichomoniasis when present 4
• Vulvar erythema and edema are significantly associated with T. vaginalis infection (OR = 2.5 for vulvar erythema) 4
• Nocturnal itching that worsens after intercourse is consistent with the marked vulvar irritation characteristic of trichomoniasis 1

Why Other Diagnoses Are Excluded

Bacterial Vaginosis (Option D) - Ruled Out

• Bacterial vaginosis presents with homogeneous white discharge and clue cells on microscopy, not flagellated protozoa 1, 2
• The frothy, yellow-green discharge excludes BV, which lacks inflammatory changes 5

Chlamydia (Option A) - Ruled Out

• Chlamydia causes mucopurulent cervicitis but does not produce flagellated organisms on wet mount 1
• While cervicitis can present with greenish discharge, the microscopic finding of protozoa is incompatible with chlamydial infection 1

Gonorrhea (Option B) - Ruled Out

• Gonorrhea produces mucopurulent cervical discharge but would show increased polymorphonuclear leukocytes on microscopy, not flagellated protozoa 1
• The wet preparation finding definitively excludes gonococcal infection 5

Clinical Significance and Management Implications

Treatment Requirements

• This patient requires metronidazole 2g as a single oral dose, per CDC guidelines 6, 2
• Sexual partners must be treated simultaneously with the same regimen to prevent reinfection, as trichomoniasis is sexually transmitted 6, 2
• Patients should abstain from sexual activity until both partners complete therapy and are asymptomatic 6

Important Clinical Associations

• Trichomoniasis is associated with increased HIV transmission risk and adverse pregnancy outcomes including preterm delivery and premature rupture of membranes 6, 7
• The infection warrants screening for other sexually transmitted infections given the shared transmission route 5

Diagnostic Sensitivity Caveat

• While wet mount is diagnostic when positive, it has only 50-70% sensitivity for detecting trichomoniasis 1, 8
• In this case, however, the protozoa were visualized, making the diagnosis certain 1