Julie Rosenthal

BASICS

DESCRIPTION

• A rare condition associated with infestation of eyelashes and eyebrows by Phthirus pubis (crab louse)

• Manifests as irritation and pruritus of eyelid margins

• P. pubis is typically transmitted by sexual intercourse with an infested individual or by the transfer of the organism from genital area to the eye by hand, clothing, and bedding.

• System(s) affected: skin/exocrine

• Synonym(s): Pediculosis ciliaris; Pediculosis pubis; Phthiriasis palpebrarum; pubic lice; crabs.

Pediatric Considerations

In children, pediculosis may be an indication of sexual abuse and involvement of social services and/or child protection agency is imperative.

EPIDEMIOLOGY

• Adolescents > Adults > Children

• Male = Female

– Men tend to have a more extensive infestation due to a greater distribution of body hair.

• Blacks = Whites

Incidence

Estimated 3 million new cases annually in the US.

Prevalence

Approximately 2% of the world population

RISK FACTORS

• Sexual activity, especially in adolescents

• Multiple sexual partners

• Sexual contact with infested individuals or contact with their clothes, towels, and bedding

• Crowded conditions

• Poor personal hygiene

Genetics

No genetic pattern

GENERAL PREVENTION

• Avoidance of sexual contact with infested individuals and their personal items

• Safe sexual practices

• Maintenance of good personal hygiene

PATHOPHYSIOLOGY

• Pubic lice are ectoparasites that feed on human blood by piercing the skin and injecting their saliva.

• Symptoms are a result of a hypersensitivity reaction to louse saliva.

ETIOLOGY

• Infestation with P. pubis (pubic louse/crab)

• Rounded, stubby, translucent parasite with 4 of its 6 legs terminating in prominent crab-like claws

• Size 0.8–1.2 mm

• Life cycle = 14 days

• Female louse lays as many as 26 ova

• Nit (louse egg) incubation period = 7 days

• Nymphs (young lice) mature over 14 days.

COMMONLY ASSOCIATED CONDITIONS

• Blepharoconjunctivitis

• Toxic follicular conjunctivitis

• Itching of the skin may lead to secondary bacterial infection.

• 1/3 of individuals may have a concomitant sexually transmitted infection.

DIAGNOSIS

HISTORY

• Complaints of severe itching and burning of the lids, especially at night

• Presence of eye irritation or conjunctival injection

• Itching in and around the pubic area or other areas heavily covered with body hair (1)[C], (2)[C]

PHYSICAL EXAM

• External examination of periorbital region at a slit lamp can demonstrate lice and nits on lids, lashes, and brows unilaterally or bilaterally.

– Lice: 1–2 mm brownish-gray specks, embedded in eyelid skin

– Nits: tiny white-gray specks, attached to the lashes or brow hair

• Evidence of follicular conjunctivitis

• Serous crusting and blood-tinged debris may be present on the lids.

• Eyelid edema suggests a severe infestation.

• Skin lesions:

– Painless blue-gray macules (maculae ceruleae) may be apparent on eyelids and cheeks. These are thought to be breakdown products of heme affected by louse saliva.

– Small erythematous papules (papular urticaria) are found at feeding sites.

• Enlargement of preauricular and submental nodes may be present on exam (3)[C].

DIAGNOSTIC TESTS & INTERPRETATION

Diagnostic Procedures/Other

Examination of a louse under light microscopy can help confirm identity of the organism if necessary.

DIFFERENTIAL DIAGNOSIS

• Seborrheic blepharitis

• Allergic blepharitis

• Herpes simplex blepharitis

• Keratoconjunctivitis sicca

• Demodex folliculorum

• Eyelid malignancies

• Eczema

• Rosacea

• Viral conjunctivitis

TREATMENT

Mechanical removal of lice and nits

MEDICATION

First Line

• A bland ophthalmic ointment, such as erythromycin, applied to lids and lashes twice daily for 10 days.

• Permethrin 1% cream rinse or pyrethrin with piperonyl butoxide shampoo/mousse

– Applied to the affected nonocular area and washed off after 10 min (4)[A]

Second Line

• Malathion 0.5% lotion

– Applied to the nonocular affected area and washed off after 8–12 h (4)[A]

• Lindane 1% shampoo

– Applied to the nonocular affected area and washed off after 4 min (4)[A]

ADDITIONAL TREATMENT

General Measures

• Bedding and clothing must be decontaminated or kept away from body contact for at least 72 h.

– Machine wash with water at least 55°

– Dryer on hot cycle at least 5–10 min

Issues for Referral

• All patients should undergo thorough examination of genital area, even if no symptoms are present.

• Up to 30% of individuals with pediculosis pubis have at least 1 other sexually transmitted infection.

– Additional testing is highly recommended.

Additional Therapies

• Oral ivermectin should be considered with resistant infestation.

– 250 μg/kg orally, repeated in 2 weeks (5)[C]

Pregnancy Considerations

Lindane and ivermectin should not be used by pregnant or lactating women due to small possibility of toxicity and side effects (4)[A].

ONGOING CARE

FOLLOW-UP RECOMMENDATIONS

Patients with pubic lice are recommended to notify their sexual partners who also require treatment.

PATIENT MONITORING

Patients should be reexamined for presence of lice/nits after 1 week of treatment.

PATIENT EDUCATION

• Patients should be advised to avoid close bodily contact with others until they and their partners have been fully treated.

• Condoms do not prevent transmission.

PROGNOSIS

• Re-treatment may be necessary if lice or nits are present at follow-up examination.

• Patients who do not respond to initial treatment should be provided with an alternative.

COMPLICATIONS

Secondary bacterial infections

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