Chapter 282

This chapter discusses the common foot disorders that are likely to present to the ED. Patients with chronic or complicated foot problems generally should be referred to a dermatologist, orthopedist, general surgeon, or podiatrist, depending on the disease and local resources. Tinea pedis, foot ulcers, and onychomycosis are discussed in Chapter 247, Disorders of the Hands, Feet, and Extremities. Puncture wounds of the foot are discussed in Chapter 50, Puncture Wounds and Bites. Foot ulcers and osteomyelitis are also discussed in Chapter 219, Type 2 Diabetes Mellitus.

Pressure or irritation causes focal hyperkeratotic lesions of the skin of the foot. The cause of these lesions can be external (poorly fitted shoe) or internal (bunion). These areas of epidermal accumulation are called calluses. Calluses are protective and should not be treated if they are not painful. Calluses grow outward but are soon pushed inward by continued pressure and become corns. Corns also develop in areas of scarring and between toes. Corns are classified as hard or soft. Hard corns are seen over bony protuberances where the skin is dry. Soft corns are seen between toes where the skin is moist. Corns may be painful or painless, but pressure on the corn usually produces pain. Corns interrupt the normal dermal lines and can thus be differentiated from calluses, which do not interrupt the normal dermal lines. Hard corns may resemble warts. However, when warts are pared, warts bleed and corns do not. Soft corns resemble tinea, and identifying tinea is important for proper treatment (see Chapter 247, Disorders of the Hands, Feet, and Extremities).1,2

Keratotic lesions may be an indication of more severe underlying disease, deformity, local foot disorder, or mechanical problem. Differential diagnosis of keratotic lesions includes syphilis, psoriasis, arsenic poisoning, rosacea, lichen planus, basal cell nevus syndrome, and, rarely, malignancies.2

### Treatment of Corns

Treatment of symptomatic corns consists of local anaesthesia, paring with a #15 blade scalpel, and removing the central keratin plug. This procedure may provide almost complete pain relief.3 Recurrence can be prevented by weekly gentle trimming with a pumice stone or emery board after soaking the lesion in warm water for 20 minutes. Application of a pad on or around the lesion to relieve pressure and avoiding constrictive footwear also provide benefit. The use of keratolytic agents is controversial. Patients should be referred to a podiatrist because therapy includes repeated paring and possibly surgery to correct any underlying source of pressure.1–3

Plantar warts are caused by the human papillomavirus. Plantar warts are fairly common and contagious. They may be painful and are usually found over bony prominences. Single lesions are endophytic and hyperkeratotic. A mother-daughter wart is similar to a single lesion except for a small vesicular satellite lesion. Mosaic warts are often painless, closely grouped, and may coalesce. Diagnosis is clinical. Daily application of 15% to 20% topical ...

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