A 64-year-old male presents to the clinic complaining of dry, flaky skin between his toes with noticeable redness. This has been present for at least a week. He denies pruritus and has not scratched in between his toes. There is no history of trauma. He wears socks with his shoes but has not been wearing his compression stockings for the past several weeks. His self treatment includes using lotion in and around his toes without any relief.
The patient denies fever, chills, nausea, vomiting or pain in his foot. There has been no change in laundry soap. He has had his current shoes for approximately one year.
The physical exam reveals maceration and erythema between all toes on both feet. Sheets of dry, flaking skin are present on the adjacent sides of toes. There is no lymphangitis or lymphadenopathy. His vital signs are all normal.
1) What is the most likely diagnosis?
2) What are some differential diagnoses?
3) What are the diagnostic tests that one can do?
4) What is the treatment for this condition?
Answering The Key Diagnostic Questions
1) The most likely diagnosis is erythrasma.
2) Differential diagnoses include seborrheic dermatitis, acanthosis nigricans, allergic contact dermatitis, cutaneous candidiasis, intertrigo, irritant contact dermatitis, plaque psoriasis and tinea pedis.
3) Under a Wood lamp (ultraviolet light), there is a characteristic coral red fluorescence due to porphyrin production. One can also send scrapings for culture.
4) Treatment includes topical erythromycin or clindamycin. If severe, one can use oral erythromycin or tetracycline. Controlling peripheral edema aids in decreasing a macerated environment. Gauze or cotton balls can keep toes spread apart to also decrease maceration. Using antibacterial soaps and drying between the toes can improve hygiene. If fungus or yeast organisms are also present, one can prescribe antifungal creams.
A Closer Look At Erythrasma
The most likely diagnosis for this patient is erythrasma. It is caused by Corynebacterium minutissimum, which invades the upper third of the stratum corneum. This organism resides in intercellular spaces and within cells, and destroys keratin fibrils. In an environment of heat and humidity (tropical regions), this organism can proliferate.
The incidence of erythrasma increases in African-American patients as well as those with profuse sweating, obesity, diabetes, increased age, patients who are immunocompromised and patients with poor hygiene. The incidence of erythrasma is equal among males and females.
The most common area of the body affected is the foot. Erythrasma can also occur in the groin, armpit, intergluteal fold, periumbilical and inframammary areas.
The skin lesions of erythrasma start as pink patches that are well defined with scales. As the infection progresses, the pink and red color turns to a brown and scaly appearance. Fissures are common. Local erythema is present. Excoriations are not usually visible because the area typically is not pruritic. Maceration between the toes is often visible.
The prognosis for patients with erythrasma is excellent with topical and/or oral treatment. Decreasing moisture and improving hygiene will help prevent recurrence.
Current Insights On Making A Differential Diagnosis
Seborrheic dermatitis. This is a papulosquamous disease that appears as a mild patch to thick crust. Symptoms can include burning, scaling and itching. Seborrheic dermatitis occurs more often in spring and winter, mostly on the scalp, face or trunk. The condition mostly has a clinical diagnosis. Treatment is corticosteroids.
Acanthosis nigricans. This condition is brought about by factors that start keratinocyte and fibroblast proliferation. Acanthosis nigricans might be a sign of malignancy. The most common cause is insulin resistance.
Allergic contact dermatitis. This consists of papules that itch with vesicles on an erythematous base. One can diagnose allergic contact dermatitis by KOH test, biopsy or patch testing. The treatment is corticosteroids.
Cutaneous candidiasis. This condition is caused by yeast such as Candida albicans. Cutaneous candidiasis happens most often in neonates and immunocompromised patients. The treatment is topical miconazole.
Intertrigo. This is mostly caused by Candida organisms. Intertrigo is caused by increased heat and maceration between opposing skin surfaces that rub together. This can happen in the very young or very old.
Irritant contact dermatitis. Scaling with mild erythema and edema are hallmarks of irritant contact dermatitis. It occurs because of a direct chemical damage to the skin, activating inflammatory mediators from epidermal cells. This condition affects women more than men and those with dry skin are more susceptible.
Plaque psoriasis. Plaque psoriasis is a chronic, recurring inflammatory skin disorder. Patients will have raised, red palpable skin lesions greater than or equal to 1 cm. The borders are well demarcated. Plaque psoriasis arises on the elbows, scalp, trunk and knees. One would diagnose this by skin biopsy. Treatments include corticosteroids and/or phototherapy.
Tinea pedis. Fungal organisms cause tinea pedis. The condition is commonly pruritic so excoriations are often visible and patients may get a secondary bacterial infection. Tinea pedis is caused by poor hygiene, hyperhidrosis or excessive heat. The treatment is topical antifungals.
Erythrasma is a bacterial skin condition caused by Corynebacterium minutissimum. It may appear in the early or chronic stages, but can usually resolve with topical erythromycin. If the condition is severe, oral erythromycin may be necessary. In regard to preventing recurrence, one can discuss simple steps with patients such as changing socks if wet, washing with antibacterial soap and drying well in between the toes, and using foot powder if hyperhidrosis is present. It is important to tell your patients not to scratch in between their toes as ulceration and other bacterial infection may occur.
Dr. Couture is affiliated with the Central Texas Veterans Health Care System in Temple, Texas.
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