-IBIS-1.5.0-
tx
cutaneous system
lice/scabies
diagnoses

definition and etiology

definition:
scabies is a parasitic disease of itch mites; they burrow under the skin and lay eggs, causing the host to itch.
lice, on the other hand, live on the host or in the clothing

etiology:
• scabies mites are transmitted person to person, usually from prolonged contact; the itching from scabies is from a hypersensitivity reaction which may take days or weeks to develop
• lice are transmitted person to person and also frequently by bedding and clothing

signs and symptoms

signs and symptoms: scabies
• characterized by intense itching, skin burrows, and occasionally secondary infections; itching is generally worst at bedtime
• lesions and burrows are seen in the finger webs, wrists, beltline, groin, areola in females, and lower buttocks; they will usually be observed in various stages of development, from papular to excoriated by itching to scabbed over

signs and symptoms: lice
• lice may produce tiny black specks in the patients undergarments, which are excreta
• nits may be seen at the base of hair, especially in pedicularis pubis (crab lice)
• mild excoriations may be seen from scratching

lab findings:
identification of offending organism by scraping from bottom of lesion and examining microscopically

course and prognosis

• Treatment with topical applications generally stops the conditions. Complications arise from superficial infection of the burrows and contact dermatitis from the topical application. In all cases it is important to clean clothes, sheets, pillows etc. along with treatment.

• Since the skin reaction to scabies is one of delayed hypersensitivity, it may be several days or weeks before a previously unexposed patient develops symptoms. For the same reason, a symptomatic patient may not become symptom-free until a week or more after treatment, when the reaction settles down.

• Typhus, trench fever, and bubonic plague are transmitted by lice.

differential diagnosis

• spider bites or other insect bites
• contact dermatitis
• atopic dermatitis
• other skin conditions producing clusters of pruritic lesions


footnotes