Download A guide to skin conditions of the feet

Derm Dec NH 2
13/12/2005
12:14
Page 1
A guide to skin
conditions of the feet
Dermatological foot problems can often be misdiagnosed and hence
mismanaged, writes Hilda O’Shea
Forum
Dermatology
Figure 1. Athlete’s foot – tinea pedis.
Figure 2. Paronychia.
FOOT PROBLEMS present in a dermatological context in general practice frequently. They often be misdiagnosed and
hence mismanaged. This article describes the most
common skin conditions of the feet I would see on an average week in general practice. Often these conditions are
picked up incidentally during the course of a consultation
for some other complaint.
Athlete’s foot – tinea pedis
This is the commonest dermatophyte infection in the
developed world. Three species that predominantly reside
on humans are Trichophyton rubrum, Trichophyton mentagrophytes and Epidermophyton floccosum. Together they are
responsible for the majority of cases. They can be responsible for toenail infections and often occur simultaneously.
Toe web infection
It can present as toe web maceration; look especially
between the fourth and fifth toe. This is the commonest presentation and age of onset is usually in the teens. Males are
affected more frequently than females.
Tight-fitting shoes and moist conditions favour growth of
the fungus. It’s usually asymptomatic, but it can be very
itchy and foul smelling, with exacerbations in hot, humid
weather. Treatment is with topical anti-fungals.
It can be complicated by secondary infection with staphylococcus aureus and haemolytic streptococci, with
development of impetigo or erysipelas.
These require a broad spectrum of antibiotics, orally, to
clear, as well as topical anti-fungals, eg. Daktarin twice daily
for three weeks and/or Lamisil once daily for one week.
Figure 3. Pitted keratolysis
Application of aluminium chloride 20% may eliminate the
hyperhidrosis. The rate of recurrence is high.
Papulo-squamous hyperkeratotic plantar infection –
‘Moccasin’ type
Characterised by erythematous, scaly lesions affecting the
soles of usually one foot and is usually caused by
Trichophyton Rubrum. Differential diagnosis is psoriasis or
juvenile plantar dermatosis. This usually needs systemic
treatment with, for example, Lamisil 250mg daily for two
weeks or Sporanox 200mg twice a day for one week.
Vesico-pustular plantar infection
Affects the side and sole of the foot, with a cluster of blisters, itchy and spreading. It is usually caused by
Trichophyton mentagrophytes. Differential diagnosis here is
pustular psoriasis. Treatment is with topical anti-fungals initially and then with systemic Lamisil later if the skin
scrapings are positive.
Paronychia
With this, the base of the nail is inflamed and swollen. It
may be acute or chronic and it often occurs in association
with an ingrowing toenail. The commonest pathogen here is
Candida, which can be mixed with staphylococci. Treatment
has to be combined: oral Erythrocin for two to three weeks,
Fucidin cream daily and oral anti-fungals for one to two
weeks. Soaking – potassium permanganate twice daily for
five days – can be a great help too.
Pitted keratolysis
This keeps turning up and is very satisfactory to treat. It
presents as a honeycomb appearance on the sole of the foot.
FORUM December 2005 41
Derm Dec NH 2
13/12/2005
12:14
Page 2
Forum
Dermatology
Hyperhidrosis is often present too and malodour. Treatment
is both topical and systemic: antibacterial cream, eg.
Fucidin and Erythrocin 500mg twice daily for one week.
Prevention of recurrence can be accomplished with control of hyperhidrosis and keeping feet cool and dry with
frequent change of cotton socks and open shoes; sandals if
possible. Patients should not wear the same shoes continuously – dry them out and wear boots for short periods only.
Juvenile plantar dermatosis
This is characterised by dry fissured dermatitis of the plantar surface of the forefoot. Occurs in young boys aged three
to 15 years and is associated with wearing occlusive
footwear, ie. trainers and nylon socks. It is related to friction.
The plantar surface is dry, red and glazed with a cracked
appearance. It is symmetrical on both feet. Treatment is
with topical preparations such as coal tar creams and white
soft paraffin.
Topical steroids are of no benefit. If fissures are the problem, superglue can be applied and that will relieve the pain.
Psoriasis of the foot
This presents as a scaly, red, well demarcated plaque on
the side of the feet or soles, with sparing of the instep. Differential diagnosis is for Tinea Pedis and hyperkeratotic
plantar eczema. Usually there is psoriasis at other sites and
a positive family history to help with the diagnosis.
Other presentations include pustular psoriasis of the foot,
again usually symmetrical and affecting the instep. It is
mainly characterised by erythematous plaques with white
and yellow pustules on the soles and older lesions being a
red-brown colour. This occurs mainly in the older population. It responds well to topical steroids and plenty of
emollients. More severe cases may need referral for retinoids
or methotrexate.
All the above cases should have skin scrapings taken to
rule out or confirm fungal infection. When mycology is positive, anti-fungals can be started. Skin scraping is a simple
test to perform: just scrape the skin lightly with the back of
a scalpel blade and let it fall onto dark paper, preferably
black (can be bought in art shop and cut up into little
squares).
It’s well worthwhile and can produce positive results when
least expected and make treatment more specific. The other
pitfall to avoid is applying steroid cream blindly and hoping
for the best; if it’s a fungal infection, it will surely make it
worse – Tinea Incognito.
In very small children look for scabies lesions on the soles
of the feet.
Hilda O’Shea is in practice in Cork city
To Subscribe to
Forum
World of Irish Nursing & Midwifery
Irish Journal of Psychological Medicine
Extenza Turpin
Stratton Business Park, Pegasus Drive, Biggleswade,
Bedfordshire SG18 8QB, England
Tel: +44 01767 604951 Fax: +44 01767 601640
Email: [email protected] www.extenza-turpin.com