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Key Features

Essentials of Diagnosis

  • Pruritus with excoriation

  • Nits on hair shafts; lice on skin or clothes

  • Occasionally, sky-blue macules (maculae ceruleae) on the inner thighs or lower abdomen in pubic louse infestation

General Considerations

  • A parasitic infestation of the skin of the scalp, trunk, or pubic areas

  • Head lice

    • May be transmitted by shared use of hats or combs

    • Epidemic among children of all socioeconomic classes in elementary schools

    • Adults contacting children with head lice frequently acquire the infestation

  • Body lice

    • Usually occur among people who live in overcrowded dwellings with inadequate hygiene facilities

    • Trench fever, relapsing fever, and typhus are transmitted by the body louse in countries where those diseases are endemic

  • Pubic lice may be sexually transmitted

Clinical Findings

Symptoms and Signs

  • Head and body lice are similar in appearance and are 3–4 mm long

  • Head lice

    • Can be found on the scalp or may be manifested as small nits resembling pussy willow buds on the scalp hairs close to the skin

    • They are easiest to see above the ears and at the nape of the neck

  • Body lice

    • Itching may be very intense

    • Scratching may result in deep excoriations, especially over the upper shoulders, posterior flanks, and neck

    • In some cases, only itching is present, with few excoriations seen

    • Pyoderma may be presenting sign

  • Pubic louse infestations

    • Occasionally generalized, particularly in hairy individuals

    • May even be found on the eyelashes and in the scalp

Differential Diagnosis

  • Head lice

    • Seborrheic dermatitis

    • Impetigo

    • Hair casts (hair debris)

  • Body lice

    • Scabies and bedbug bites

    • Impetigo

    • Dermatitis herpetiformis

    • Urticaria

  • Pubic lice

    • Anogenital pruritus

    • Scabies

    • Atopic dermatitis (eczema)

Diagnosis

  • Relies on an index of suspicion and isolating the organism

  • Head lice

    • Diagnosis is made by finding lice on the scalp or small nits resembling pussy willow buds on the scalp hairs close to the skin

    • Nits are easiest to see above the ears and at the nape of the neck

  • Body louse

    • Seldom found on the body

    • Must be looked for in the seams of the clothing

  • Pubic louse

    • Occasionally generalized, particularly in hairy individuals

    • Diagnosis is made by finding lice or nits on pubic hair, body hair, or eyelashes

Treatment

Medications

Table 6–2.Useful topical dermatologic therapeutic agents.

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