Phthiriasis palpebrarum - An easily missed diagnosis

Abstract

We report a case of phthiriasis palpebrarum, which was previously misdiagnosed as anterior blepharitis. Several lice and multiple nits were noted on the eyelashes in left eye under slit-lamp examination. The patient was successfully managed by mechanical removal of lice and nits after applying 20% fluorescein dye and subsequent treatment with 0.5% moxifloxacin eye ointment containing soft paraffin as the base.

PHOTO ESSAY

A 39-year-old female presented to our OPD with complaints of severe itching of left eye of one-month duration which was previously misdiagnosed as anterior blepharitis. Several lice and multiple nits were noted on the eyelashes in her left eye under slit-lamp examination [Figure 1a and b]. Her best-corrected visual acuity was normal in both eyes. The patient was managed by mechanical removal of lice and nits after applying 20% fluorescein dye and subsequent treatment with 0.5% moxifloxacin eye ointment containing soft paraffin as the base. After instillation of topical anesthesia (proparacaine eye drops) on the conjunctival cul-de-sac, the patient was asked to gently close the lids. Twenty percent fluorescein dye was then applied over the eye lashes and eye brows of both the eyes with the help of sterile cotton-tipped applicator. Thirty minutes were allowed for the fluorescein dye to dry and to have its effect on the parasites. The patient was instructed to keep her lids closed during this period. The remaining adult parasites and nits were mechanically removed with the help of blunt forceps. She was then prescribed 0.5% moxifloxacin eye ointment with soft paraffin as the base, for thrice daily application, for 10 days. She was seen 1 week later and few nits were remaining. The same procedure of mechanical removal after application of 20% fluorescein dye was repeated in order to remove the remaining nits. She was again seen after 1 week and after 1 month. Her lids were clean and completely parasite free at these follow-up visits [Figure 2]. The patient was advised dermatology consultation.

Figure 1: (a) Slit-lamp image showing louse with nits on the lid margin. (b) Magnified view of the parasite with nits

Figure 2: Slit-lamp image taken 2 weeks after starting treatment

DISCUSSION

Phthiriasis palpebrarum is an ectoparasites of the eyelashes because of an infestation with phthiriasis pubis, also known as pubic louse or crab louse. It is a rare entity and can be confused with blepharitis.[¹] Probably a large number of cases are being missed since it mimics anterior blepharitis clinically and often misdiagnosed as conjunctivitis or blepharitis.[²] The nits and adult lice harboring the lashes of the eye can also be easily missed. It can present with clinical features like excessive itching, lid hyperemia, and excoriated skin. It is frequently misdiagnosed as allergic conjunctivitis or blepharitis due to deep burial of the ectoparasites and the presence of crusts on the eyelashes.

Phthiriasis palpebrarum is caused by phthiriasis pubis, a hematophagous arthropod, an obligate parasite of human beings. It is an insect belonging to pthiridae family and phthiriasis genus. Adults measure up to 2 mm long and are smaller than the head lice and body lice.[¹]

Infestation with phthiriasis pubis occurs mainly through sexual intercourse or during interactions between infested parents and their children. It generally affects both eyes and unilateral involvement is less common. But in our patient, we noted the infestation only in left eye.

Several topical treatments may be used in phthiriasis palpebrarum. This includes manual removal of adult parasites and nits using forceps, 0.3% tobramycin eye ointment, 0.5% moxifloxacin eye ointment with paraffin as the base, parasympathomimetic agents (physostigmine ointment, 4% pilocarpine gel), liquid Vaseline, topical botulinum toxin, 20% fluorescein dye, etc., Argon laser therapy, cryotherapy, 1% gamma-benzene hexachloride cream, 1% mercuric oxide ointment, malathion shampoo, permethrin 5% ointment, 50% tea-tree oil, and lindane are also described. Application of 20% fluorescein dye causes immobilization of parasites, facilitates their mechanical removal, and reduces the risk of accidental infestation of treating physician.[³] The paraffin base in ophthalmic ointment acts as a suffocating agent to kill the lice and the antibiotic component helps to prevent secondary bacterial infection. All sexual contacts and family members of the infested person should be evaluated for the presence of phthiriasis pubis and phthiriasis palpebrarum and if necessary, they have to be treated. The patients should get counseling regarding personal hygiene and cleaning of linens and clothing. The prognosis of phthiriasis palpebrarum is good in majority of cases.

Application of 20% fluorescein dye, mechanical removal of the parasites and nits, and topical application of ophthalmic ointment with paraffin base are effective in the treatment of phthiriasis palpebrarum.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given her consent for her images and other clinical information to be reported in the journal. The patient understands that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

Acknowledgements

We would like to express our sincere gratitude to Mr. Ajmal (Research assistant, Comtrust Charitable Trust Eye Hospital, Kozhikode) for his technical assistance.