Treating A Patient With Bilateral Rashes And Intense Itching On The Top Of The Feet

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Author(s): 
William Fishco, DPM, FACFAS

   Atopic eczema is the main differential in this case. Atopy or atopic syndrome is a predisposition to develop a hypersensitivity to an allergen. Atopy generally begins in infancy with rashes on the face (cheeks). It is relatively uncommon for people to develop atopic eczema later in life and therefore, the history is usually a key element in the differential diagnosis. Generally speaking, with atopic eczema, there is a strong history of asthma, hay fever and/or environmental allergies with these patients. With atopic eczema, the anterior aspect of the ankle is a common location and scratching can lead to lichenification of skin.

   Contact dermatitis is caused by an allergic reaction to the skin. Irritant contact dermatitis is usually caused by chemicals such as industrial solvents, latex and soaps. Allergic contact dermatitis can be caused by sensitivity to metal (nickel and gold) and plant material such as poison ivy. Shoe contact dermatitis can be caused by hypersensitivities to glue, rubber, dyes and tannins. A shoe contact dermatitis can lead to a symmetrical pattern of rash on the feet.

   Lichen simplex chronicus, the correct diagnosis in this case, is also known as neurodermatitis. It has been considered to be associated with anxiety disorders. Sometimes minor skin irritations such as a bug bite, clothing or sheets on the skin can initiate the itch. Repetitive scratching leads to inflammation of skin (redness), excoriations and ultimately lichenification. The dorsal aspect of the foot is commonly involved due to taking one’s heel and repetitively rubbing the contralateral dorsal foot. Other common areas affected include the nape of the neck, bony prominences such as the lateral malleolus, and the groin including the genitals. Only areas that are easily accessible by hand scratching can be involved.

   The patient had a strong history of an itch-scratch-itch cycle. He had no history of atopy. A skin scraping was negative for fungal infection. He ultimately responded well to a taper dose of prednisone and super high potency topical steroid ointments.

How To Treat Lichen Simplex Chronicus

Treatment of lichen simplex chronicus requires super high potency topical steroids. Lower potency topical steroids are ineffective as was the case in this patient. Oftentimes, patients should use the super high potency steroid under occlusion for two to three days to jump-start its effect. This should reduce the itch in an attempt to break the itch-scratch-itch cycle. Obviously, the patient needs to stop scratching, which is exacerbating the entire condition. Antihistamines such as diphenhydramine can help to reduce pruritus. Keeping the skin moisturized is important as well. Finally, if there is an obvious anxiety disorder element, then the patient may require oral anxiolytic agents.

   The key to diagnosing this rash was the lack of atopy in the patient’s history. One can obtain a serum level of IgE to rule out an allergic component if there is uncertainty in the patient’s history. Also, although it is rarely needed, one can perform a punch biopsy as well as scratch testing. These tests would confirm inflammatory/hypersensitivity conditions versus infectious (tinea pedis) or mechanical irritation (lichen simplex chronicus). In the aforementioned case presented, the features of the rash included an inflammatory skin eruption (as noted by the erythematous base), lichenification, scale and fissuring of skin.

   Dr. Fishco is board-certified in foot surgery and reconstructive rearfoot and ankle surgery by the American Board of Podiatric Surgery. He is in private practice in Phoenix. Dr. Fishco is also a faculty member of the Podiatry Institute.

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