Page 407 - Medicine and Surgery

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Chapter 9: Infections of the skin and soft tissue 403

Tinea Unguium: Nail infection with ringworm is Management

common especially in the elderly. Patients develop Topical shampoo containing insecticides such as mala-
asymmetrical discoloured (white/yellowish black) thion and permethrin may be used, although there
thickened nails with crumbling white material un- is some evidence of increasing resistance. Treatment
der the nail plate. This condition may respond to a should be repeated after 7 days. Mechanical removal of
prolonged course of systemic antifungals as for tinea lice nit combs from wet hair is an alternative strategy.
capitis. Household members should be examined and treated if
Tinea Cruris: Tinea cruris affects the groin with ery- infested.

thema and scaling is surrounded by a well-defined
edge. Infection may extend over the perianal region. Scabies
If mild, treatment is with topical antifungals. Severe
or refractory cases require oral antifungals as for tinea Definition
capitis. Skin infestation by the mite Sarcoptes scabiei, causing
itching.
Parasitic skin infections Aetiology/pathophysiology
Transmission of the mite occurs by skin–skin contact
Head lice with an infested individual or contaminated clothing
or bedding. The mite burrows down into the stratum
Definition
corneumof the skin and then the female lays eggs.
Infestation with the head louse Pediculosis capitis.
Clinical features
Incidence There is often a widespread, erythematous urticating
Common rash all over the body as a result of a hypersensitiv-
ity reaction to the mite. Patients present with severe
itching usually worse at night.
Age
On examination small papules and linear tracks,
Occurs mainly in school children.
caused by burrowing mites, are seen around the
wrists, finger webs and ankles (and scrotum in the
Sex male).
F > M(due to longer hair). In immunosuppressed patients, Norwegian/crusted
scabies may occur with diffuse scaly erythematous
Aetiology/pathophysiology patches especially on the scalp, hands and feet.
Pediculosiscapitisorheadlouseisagrey-whiteinsectthat
grasps on to hair and sucks blood. Eggs laid by the female Investigations
are closely adherent to hair. Insects are spread by contact The burrows and distribution pattern is very suggestive
but as insects can survive for hours away from the host, of the diagnosis. The mite can be visualised using a der-
transfer on clothing, shared combs, towels and beds may matoscope.
occur.
Management
Clinical features Patients are extremely infectious and require barrier
Infestations are often asymptomatic although allergy nursing. The entire skin except the face should be treated
may result in itching and lymphadenopathy. The head with malathion or permethrin. All close contacts re-
louse is difficult to find but eggs (nits) may be seen along quire treatment, and clothing and bed linen should be
the hair shaft. A fine-toothed nit comb is often used to thoroughly machine-washed. Norwegian/crusted sca-
detect lice and nits. bies may require repeated treatments.