A 36-year-old active duty service member presented with an acute exacerbation of a chronic rash on the dorsal surface of both feet.
History. Four years prior, the rash initially appeared on the dorsum of his right foot without any known triggers. Although the rash always spontaneously resolved, it continually recurred during the summer months.
His current presentation was actually precipitated during the winter months, with the rash initially appearing on the dorsum of the right foot shortly before involving the left foot. He denied the use of any new soaps, lotions, or detergents as well as contact with ticks, plants, or other foreign substances. Other than pruritus at the rash site, he was asymptomatic.
The patient maintained good health and endorsed an intentional 40 lb weight loss by running more than 10 miles on a weekly basis. He denied recent antibiotic use and sexually transmitted infections.
Physical examination. The patient appeared healthy with normal vital signs. The dorsal surface of both feet demonstrated an erythematous macular rash (Figures 1-3). The affected areas were dry and notable for scaling and crusting. The skin was not warm or tender to touch and blanched with palpation. There were no bullae or vesicles and no evidence of skin necrosis. Both feet had normal motor-sensory function. Several of the toenails appeared black, but there was no involvement of the soles or interdigital spaces.
Discussion. This is classic shoe dermatitis, which is an allergic contact dermatitis due to leather and/or the dyes used to color them. While allergic contact dermatitis consists of erythematous, indurated, scaly plaques localized to the area of the skin that comes in contact with the allergen, specific involvement of the dorsal surface of the foot suggests the diagnosis of shoe dermatitis. The dorsum is involved most frequently because of its greater surface area, thin stratum corneum, and sustained interaction with the upper portion of the shoe.1
The most common symptom of allergic contact dermatitis is pruritus.1 While diagnosis of allergic contact dermatitis is primarily clinical, patch testing can unequivocally determine the presence of a true allergen.2 Treatment generally consists of avoidance of the allergen and topical corticosteroids.3
Differential diagnosis. Chronic plaque psoriasis presents with symmetrically distributed cutaneous plaques that are raised above the surrounding normal skin and display sharply demarcated borders.4 The plaques are typically asymptomatic and display a thick silvery scale. The scalp, extensor elbows, palms, soles, and nails are frequent areas of involvement.
Chronic tinea pedis begins as slowly progressive, pruritic, erythematous erosions, and scales between the toes that can extend onto the sole, sides of the foot, and in some cases the top of the foot. The margin between involved and uninvolved skin is distinctive. Onychomycosis is also an associated feature. Although history and clinical examination are characteristic, potassium hydroxide examination of scrapings from the lesions can differentiate between tinea pedis and plantar psoriasis and foot eczema.5
Dyshidrotic eczema presents as an idiopathic intensely pruritic, chronic and recurrent, vesicular dermatitis involving the palms and soles. The vesicles desquamate over a 1- to 2-week period, leaving slowly resolving erosions and fissures on the skin.6
- Matthys E, Zahir A, Ehrlich A. Shoe allergic contact dermatitis. Dermatitis. 2014;25(4):
- Bourke J, Coulson I, English J; British Association of Dermatologists. Guidelines for care of contact dermatitis. Br J Dermatol. 2001;145(6):877-885.
- Bourke J, Coulson I, English J, et al. Guidelines for the management of contact dermatitis: an update. Br J Dermatol. 2009;160(5):
- Tollefson M, Crowson C, McEvoy M, Maradit Kremers H. Incidence of psoriasis in children: a population-based study. J Am Acad Dermatol. 2010;62(6):979-987.
- Gupta A, Cooper E. Update in antifungal therapy of dermatophytosis. Mycopathologia. 2008;166(5-6):353-367.
- Guillet M, Wierzbicka E, Guillet S, et al. A 3-year causative study of pompholyx in 120 patients. Arch Dermatol. 2007;143(12):