Recurring tinea pedis
A 44-year-old woman with type 2 diabetes of 6 years' duration developed itchy vesicles on the border of her foot associated with dry skin, desquamation and pruritus (Fig. 2.11 ). We prescribed Whitfield's ointment which she
Fig. 2.12 Verruca.
used for 1 week. Three weeks later the problem recurred. She was advised to continue using the Whitfield's ointment until 2 weeks after the symptoms had resolved, and then to apply surgical spirit to the previously affected areas after washing them daily and drying them carefully. She was also advised to wear clean socks every day and dust her feet and interdigital areas with Mycil powder. The problem did not recur.
' Treatment of fungal infections should be continued for
2 weeks after symptoms have resolved • Prophylaxis with Mycil may be necessary to prevent recurrence.
Fissures are moist or dry cracks in epidermis at sites where skin is under tension. Deep fissures may involve dermis.
Fissures can occur in dry skin, when the treatment is an emollient, such as E45 cream, olive oil or coco butter, or in wet skin, where an astringent or antiperspirant such as aluminium chloride is helpful.
Warts may occur anywhere on the foot and may be single or multiple, and appear as round flattened papules or plaques. They are whitish or grey in colour with a rough surface (Fig. 2.12).
If they are on the plantar surface and thus subjected to pressure from walking, they may be difficult to distinguish from corns. However, warts are painful when they are squeezed while corns are painful when they are pressed. Skin striations are interrupted by warts but not by corns. Removal of a verruca by scalpel debridement reveals tiny reddish brown dots. Dots are not visible following removal of corns.
Small speckles of black (thrombosed blood vessels) can be a sign that the verruca is resolving spontaneously.
Accumulation of hyperkeratosis may cause pain on walking: excess keratin can be pared with a scalpel by the podiatrist or the patient may use a pumice stone. However, warts do not need to be treated unless they are painful or spreading: most will resolve within 2 years without treatment.
Some swimming pools require people with verrucae to wear verruca socks to avoid cross-infection.
The recommended treatment for ablation of painful or spreading verrucae in people with diabetes is cryotherapy with liquid nitrogen. The resulting breakdown of tissue should be kept clean and covered with a dressing. However, treatment with liquid nitrogen can cause severe pain and ulceration and should only be used on stage 1 feet. Treatment with strong acids or silver nitrate is not recommended in diabetic patients.
Sometimes surgical treatment with excision of the wart is required.
Patients should be warned not to self-diagnose or self-treat warts. Some foot malignancies present as wart-like lesions.
These are superficial accumulations of clear fluid within or under the epidermis which develop following trauma to the skin. Common causes include unsuitable shoes, failure to wear socks and walking in wet footwear. Pedal bullae are sometimes associated with hypoglycaemic episodes.
Several serious lesions, including early neuropathic and early ischaemic ulcers, pressure ulcers, burns, puncture wounds and infections complicating ulceration, may first present as a bulla.
Unless bullae are small, superficial and containing clear fluid, they should be regarded as stage 3 lesions.
Small, flaccid bullae can be cleaned and covered with a sterile non-adherent dressing. Large bullae (over 1 cm in diameter) and all tense bullae should be lanced with a scalpel and drained before dressing. Aspiration with a syringe is less useful because the hole frequently seals, fluid accumulates again and unrelieved hydrostatic pressure causes extension of the blister.
The cause of blisters should always be ascertained and addressed.
This is a rare condition where diabetic patients present with intraepidermal blisters which are not associated with trauma and heal without scarring. Treatment of bullosis diabeticorum is as for bullae (see above).
and can spread to draining lymph nodes. Suspicious lesions should be biopsied. Treatment is surgical excision.
These are localized inflammatory lesions, provoked by cold and injudicious reheating. Chilblains are frequently found on the toes. Initially they are white due to vasoconstriction, but usually present as dusky red swellings which are intensely pruritic in the acute stages. When they become chronic they present as purplish lesions. They are best managed by taking preventive measures. Patients should avoid standing in the cold and damp, and should refrain from toasting their toes in front of the fire when their feet are chilled. In the cyanotic phase compound tincture of benzoin BP maybe used.
Although skin malignancy is rare in the foot, the diagnosis should be considered, especially in unusual and non-responsive conditions.
It is important to be aware that squamous cell carcinoma, malignant melanoma and, very rarely, basal cell carcinoma, may present in the foot.
It may present as a reddish plaque, warty lesion, nodule or as an ulcer with undermined ragged edges. Squamous cell carcinomas are likely to arise at the site of a scar or an existing lesion such as venous ulcer or subungual ulcer. Most squamous cell carcinomas are locally aggressive
Although the most common skin tumour overall, it is very rare on feet, especially on the plantar surface, and even rarer as subungual ulcer. They are small pearly lesions which develop a central breakdown and rolled edge and are treated by cryotherapy or surgery.
Malignant melanomas arise from existing moles or spontaneously from no apparent pre-existing lesion. Some melanomas produce little or no pigmentation and are termed hypo- or amelanotic melanomas. Melanomas are usually pigmented lesions on the foot which are irregular in outline and border, and variable in colour. They may be painful. It is wise to refer without delay to the dermatologist all pigmented lesions that develop de novo, change in size, shape or colour, or develop inflammation, ulceration and bleeding.
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