Scabies

Question 1

Define Scabies

Answer 1

An intensely itchy skin infestation caused by the human parasite Sarcoptes scabiei

Question 2

Aetiology of scabies

Answer 2

Sarcoptes scabiei
Transmission through close/prolonged contact e.g. sexually acquired

Crusted = highly contagious

Question 3

Symptoms and signs of scabies

Answer 3

Generalised itch (due to delayed type IV hypersensitivity to mite and products)
- Worse at night

Erythematous papules: periumbilical/waist/genitalia/breasts/buttocks/axillary folds/interdigital spaces/wrist/extensors
Excoriation with haemorrhagic crusst
Burrows: thin, brown-grey line 0.2-1cm
Nodular lesion: penis/scrotum/buttocks/groin/axillary

Question 4

What is crusted scabies

Answer 4

(Norwegian scabies): hyperinfestation with thousands or millions of mites present in exfoliating scales of skin. It develops as a result of an insufficient immune response by the host.

generalized, poorly defined, erythematous, fissured plaques covered by scales and crusts
On bony prominences (for example, finger articulations, elbows, and iliac crest)

Question 5

Investigations for scabies

Answer 5

Ink burrow test: dark zigzagged line running across and away from the lesion appears, due to ink tracking down the mite burrow.

Microscopy of skin scarpings: Presence of mites, eggs, or mite faecal material

Question 6

Management for scabies

Answer 6

Permethrin 5%

Itching can continue for up to 4 weeks after successful treatment
- Treat with crotamiton 10%
- Definite eradication: topical hydrocortisone 1%
- Suggest sedating anti-histamine e.g. chlorphenamine

Question 7

Complications for scabies

Answer 7

Secondary bacterial infection e.g. impetigo, folliculitis, furunculosis, ecthyma, abscess
Secondary eczematization
Nodular scabies: pruritic nodules of axillae, groin, and male genitalia

Question 8

Prognosis for scabies

Answer 8

Scabies is generally associated with a good prognosis provided compliance is satisfactory and all close contacts (symptomatic or asymptomatic) are simultaneously treated
Most people with scabies are cured after two treatments with topical permethrin. However, itching may continue for up to 4 weeks after successful treatment for scabies.
Crusted scabies may need prolonged and repeated treatment, and patients may have significant underlying conditions that will influence the prognosis