Pediculosis

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 3–4 mm long and similar in appearance

• 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

• See Table 6–2