July 2006

This patient was scheduled to have an electroencephalogram (EEG) to determine if she was having seizures. The EEG technicians noticed what they thought was whitish scale in her scalp especially just over her ears. The patient was then referred to our dermatology clinic. In retrospect, the patient stated that she had some scalp itching. What is her diagnosis?

Answer

The patient has pediculosis capitis. The causative organism is Pediculus humanus capitis.

The lice are spread from person-to-person when head-to-head contact occurs. The lice can also be spread from fomites on pillowcases, hats, scarves, hoods, hair ornaments, brushes and combs, etc. The infestation is most common in school-aged children, and is more common in girls than boys.

The clinical findings in pediculosis capitis are nits; live lice, either nymphs or adults; and/or sores in the scalp, from scratching. The nits are most often found in the retroauricular or occipital areas of the scalp. Pruritus is a common symptom. Other household members should be examined for any signs of infestation.

Differential diagnoses

Seborrheic dermatitis, also known as dandruff, can be characterized by thick scale in the scalp hair. The scales move along the hair shafts with stroking while the nits are attached to the hair and do not move.

Psoriasis may have scale in the scalp, but it tends to have distinct erythematous raised plaques. Psoriatic lesions can usually be found elsewhere on the body in addition to the scalp.

Tinea capitis may have some scale in the scalp along with itching, however, hair loss is not a common finding with pediculosis capitis.

Patients with pediculosis capitis can be treated with over-the-counter preparations such as pyrethrins or permethrin crème rinse 1%. The products should be applied to dry hair for maximum effectiveness. Any other affected household members should be treated at the same time. Bed linens, especially pillowcases, should be laundered. Furniture and the floor where the child usually lays should be vacuumed. A nit comb is useful for removing the nits following treatment.

Prescription medications include lindane and malathion. For more resistant cases, the following can be used, but is off label: permethrin cream 5% (left on overnight); trimethoprim-sulfamethoxazole (orally for three days); or oral ivermectin (200 µg/kg orally one dose).

Source: Patricia A. Treadwell, MD

For more information:

• Jones KN, et al: Review of common therapeutic options in the United States for the treatment of pediculosis capitis. Clin Infect Dis. 2003;36:1355-1361.
• Ko CJ, et al. Pediculosis. J Am Acad Dermatol. 2004;50:1-12.
• Leung AK, et al. Pediculosis capitis. J Pediatr Health Care. 2005;19:369-373.
• Or, visit the CDC Web site: www.cdc.gov/ncidod/dpd/parasites/lice/default.htm.