Pediculosis: (Lice, Crabs)

Presentation

Patients arrive with emotions ranging from annoyance to sheer disgust at the discovery of an infestation with lice or crabs and request acute medical care. There may be extreme pruritus, and the patient may bring in a sample of the creature to show you. Head lice generally affect children aged 3 to 12 years.

The adult forms of head lice ( Pediculus humanus capitis ) can be very difficult to find, but their oval, light gray eggs (nits) can be readily found firmly attached to the hairs above the ears and toward the occiput. Secondary impetigo and furunculosis can occur.

The adult forms of pubic lice ( Pthirus pubis or crab lice) are more easily found, but their light yellow-gray color still makes them difficult to see. Small black dots present in infested areas represent either ingested blood in adult lice or their excreta. Maculae ceruleae (bluish-brown macules), which represent intradermal hemorrhage at sites where lice have fed, can sometimes be found. Pubic lice are not limited to the pubic region and may be found on other short hairs of the body, such as body hair, eyebrows, and eyelashes (pediculosis ciliaris).

Identification of lice or viable nits with a magnifying glass makes the diagnosis ( Fig. 176.1 ).