Essential Insights On Treating Psoriatic Lesions In The Lower Extremity

M. Joel Morse, DPM

Patients with psoriasis can present with multiple levels of involvement and with different types of the chronic condition. Accordingly, this author discusses the presentation of the condition, offers keys to diagnosis and reviews a variety of treatment options, including topical agents and combination therapy.

A patient presents to the office with symmetric, sharply demarcated, erythematous, silver-scaled patches on the back of the heels and ankles. The right foot is sore and has dried blood from constant scratching. Your immediate differential is tinea pedis, drug eruption, contact dermatitis, irritant dermatitis, eczema or psoriasis.

   A history reveals the patient has siblings with similar issues only on other areas of the body. A full body exam reveals that there is some flaking of the scalp and scaling on the neck. The patient has some yellow toenails that have yet to respond to oral antifungals despite two courses of such medication. Clotrimazole (Lotrimin), recommended by the internist, has not provided any resolution of the scaling and pruritus. What is the likely diagnosis? Psoriasis.

   As podiatrists, we can see all types of psoriasis from the most common plaque type to the least common pustular psoriasis form. The other types (guttate, inverse, erythrodermic) occur rarely in the foot and ankle. Once one recognizes psoriasis and rules it in as the correct dermatosis in question, the management/treatment depends on the type of psoriasis, extent of the disease, area of involvement and percentage of skin involved. Other factors include whether there is a known arthritis component or other comorbidities as well as the patient’s background or lifestyle. In podiatry, we generally will see those with localized psoriasis. The majority of patients with psoriasis have mild or limited psoriasis, which is generally defined as less than 20 percent body involvement.1

   Psoriasis is characterized by inappropriate activation of the cellular immune system directed against self-antigens.2 It is mediated by the T lymphocyte of the skin and is the most prevalent T cell–mediated inflammatory disease in adults.3 Psoriasis occurs as part of a complex set of interactions among genetic, immunological, systemic and environmental factors.4

   Psoriasis causes significant physical and psychosocial suffering. A study conducted in 2009 revealed that the psychosocial morbidity of psoriasis and impairment of quality of life is the same or worse than arthritis, diabetes or cancer.5

   Psoriasis is one of the most prevalent immune diseases and affects nearly 2 to 3 percent of the Caucasian population, including over 7 million Americans and an estimated 125 million people worldwide.6,2 It affects approximately 1.3 percent of the African-American population in the United States. Generally, it is more common in individuals living at higher latitudes or in colder locales, and is less common in individuals who have greater sun exposure.

   The incidence of psoriasis is much lower in dark-skinned West Africans and African-Americans than in light-skinned people of European ancestry. The incidence is also low in the Japanese and Eskimos, and is extremely low to non-existent in Native Americans in both North and South America.7

How Psoriasis Develops

In a normal human, skin cells normally take about a month to develop, mature and move to the skin’s surface, where they are continually shed. Turnover of the epidermis allows the skin to maintain its barrier function, repair injured skin in wound healing and receive the signals that stimulate or inhibit cell proliferation. In psoriasis, the skin cells mature in less than a week and move to the surface where they accumulate, resulting in the formation of scales among the red, inflamed tissues.8

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