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

William Fishco, DPM, FACFAS

A 53-year-old male presented to the office with the chief complaint of a rash on the top of both feet, worse on the right than the left. The duration of symptoms had been more than six months. He related intense itching that required scratching. His wife told me that he would wake her up due to rubbing his feet in bed. His primary care physician prescribed a course of a topical cortisone cream using triamcinolone 0.1%, which helped minimally.

   His past medical history was remarkable for hypertension, dyslipidemia, diet-controlled diabetes and gastroesophageal reflux disease. His daily medications included lisinopril (Prinivil, Merck), atorvastatin calcium (Lipitor, Pfizer) and rabeprazole sodium (AchipHex, Eisai). He denied any medication allergies. He denied any environmental or food sensitivities.

   There was no personal or immediate family history of asthma or restrictive airway disease. Prior surgeries included rotator cuff repair and an appendectomy. His habits were remarkable for current cigarette smoking of half a pack per day (30 pack year history) and alcohol consumption of approximately 14 cans of beer per week. He was married and employed as a maintenance worker. He would wear high top boots to work and sneakers after work. He denied any change in shoe gear during this episode.

   The physical exam revealed an overweight, well-dressed, well-nourished male in no acute distress. The vascular exam revealed strong palpable pulses. Capillary refill was immediate to the level of the toes. The neurologic exam revealed symmetric and equal deep tendon reflexes. No loss of epicritic sensation was present. The orthopedic exam revealed symmetric, pain-free range of motion of the ankle, subtalar and midtarsal joints.

   The dermatologic exam revealed a rash on the dorsal surface of both feet. The right foot had an erythematous base with skin scaling, fissuring and weeping. The left foot had erythema without secondary skin changes. The rash distribution was fairly symmetrical. The features of the rash included intense pruritus leading to lichenified skin, an erythematous base, scaling, fissures, wetness (weeping) and a symmetrical pattern.

Key Questions To Consider

1. What is the most likely diagnosis?
2. What is the differential diagnosis?
3. What are the key characteristics of this condition?
4. What is the treatment?

Answering The Key Diagnostic Questions

1. Lichen simplex chronicus
2. Tinea pedis, psoriasis, contact dermatitis, lichen simplex chronicus and atopic eczema
3. No history of atopy
4. Super high potency topical steroids

Pertinent Insights On The Differential Diagnosis

The differential diagnosis for common rashes with these features includes tinea pedis, psoriasis, contact dermatitis, lichen simplex chronicus and atopic eczema.

   Tinea pedis is one of the most common rashes on the foot. Typical presentations include the acute variety, which is typically wet with vesicles and blisters in the web spaces. Fissuring of skin in the web spaces is common — especially when it is macerated — and typically involves the third and fourth web spaces. The chronic type of tinea pedis is generally dry with scales, fissures and lichenification in a moccasin distribution. Although tinea pedis can occur on the dorsal foot, the most common areas to be affected are toes and the plantar foot. Tinea pedis is less likely than contact dermatitis to be symmetrical.

   Psoriasis is classified as an autoimmune disorder of the skin. Plaque psoriasis is characterized by a silvery scale on an erythematous base. Itching can be severe with psoriasis. The most common areas of the body for psoriasis to occur include the scalp, elbows, knees and back. There can be excoriations and crusting of the primary lesion. Intense scratching can lead to lichenification of skin.

   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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