Phthiriasis palpebrarum

A 77-year-old woman presented to our dermatology clinic with itching on her scalp. We diagnosed scalp pediculosis caused by pubic lice and treated the patient with 5% permethrin lotion for 3 weeks. Her scalp symptoms resolved but 2 weeks into her treatment, she developed eyelid pruritus and she returned for reassessment 3 weeks after completing the scalp treatment. No family members reported pediculosis and she denied any sexual contacts. On examination, she had numerous black–brown granules attached to the eyelashes and eyelids of both eyes (Figure 1A). Dermoscopy showed multiple lice and ovoid nits on the eyelashes and eyelids (Figure 1B). We did not find any lice or nits in the pubic, axillary or scalp region. Microscopic examination showed pubic lice (Figure 1C) and we diagnosed phthiriasis palpebrarum. We treated with 1% permethrin lotion and trimmed her eyelashes, which successfully cleared the pediculosis.

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Figure 1:

(A) Numerous black–brown granules attached to the left eyelashes and eyelids of a 77-year-old woman with phthiriasis palpebrarum. (B) Dermoscopy showed multiple lice and ovoid nits on the eyelashes and eyelids. (C) Microscopic image showing pubic louse.

Pediculosis pubis, affecting about 2% of adults, is a cutaneous parasitic infection caused by the pubic louse.1 In contrast to head and body lice, the pubic louse has a shorter and broader body with claw-like pincers on the 2 pairs of back legs.2 Pediculosis pubis is transmitted by sexual or close body contact or through fomites.1 It usually occurs in the pubic region, but may infest the scalp, axilla, eyebrows or eyelashes (phthiriasis palpebrarum).3 Phthiriasis palpebrarum presents with eyelid pruritus, burning, punctate erythema, macula cerulea, brown deposits of louse fecal matter, madarosis and conjunctival hyperemia, which must be distinguished from viral, bacterial and autoimmune conjunctivitis or blepharitis.1 Dermoscopy or slit-lamp examination are simple and noninvasive diagnostic tools.1^,3 Recommended therapies include hand picking of lice and nits, ophthalmic ointment with paraffin or yellow mercuric oxide and 1% permethrin (washed off after 10 min).1^,3 Second-line agents include pyrethrin, malathion and ivermectin.1^,3 Bedding, clothes and towels should be decontaminated by machine washing (≥ 50°C) or dry cleaning, or by sealing and storing them in a plastic bag for 3 days.1^,3 Patients should avoid close contact to stop transmission.3