A one-year diagnostic delay of Phthirus pubis infestation mimicking vulvar lichen simplex chronicus in a postmenopausal woman: a case report.

BACKGROUND: Phthirus pubis infestation is a sexually transmitted ectoparasitic disorder. Its falling global incidence over recent decades has lowered clinicians' diagnostic alertness.

CASE DESCRIPTION: We present a 56-year-old woman who had reached menopause 6 years prior, with recurrent vaginal spotting and severe nocturnal vulvar pruritus lasting for 12 months. She was initially misdiagnosed with postmenopausal abnormal uterine bleeding and vulvar lichen simplex chronicus. Multiple interventions, including hysteroscopic curettage with intrauterine device removal, oral antibiotics, hemostatic agents and long-term topical corticosteroids, failed to relieve her symptoms. During routine physical examination, clinicians identified pinpoint rust-brown parasite fecal stains on her underwear, a diagnostic clue that had been overlooked in prior visits. Repeat vulvoscopy visualized adult Phthirus pubis and nits attached to pubic hair-parasites missed in the first vulvoscopic examination 1 year earlier. Her sexual partner was concurrently diagnosed with pubic lice, confirming transmission via intimate sexual contact. The patient received complete pubic hair shaving followed by seven consecutive days of sitz baths with Stemonae Radix decoction, which fully eliminated vaginal bleeding and pruritus. Both the patient and her partner received identical anti-lice therapy and completed 6 months of follow-up without recurrence.

CONCLUSIONS: This atypical case indicates that pubic lice infection should remain a differential diagnosis for postmenopausal females with intractable vulvar complaints. For patients with vulvar pruritus refractory to standard topical regimens, gynecologists must conduct thorough inspection of pubic hair and implement early vulvoscopy or dermoscopy to rule out ectoparasites and avoid prolonged mismanagement.