Essential Insights On Treating Psoriatic Lesions In The Lower Extremity

M. Joel Morse, DPM

   Psoriasis is a hyperproliferative disorder of keratinocytes.9 The lesions of psoriasis are distinctive. They begin as red, scaling papules that coalesce to form round-to-oval plaques, easily distinguishable from the surrounding normal skin.10 The primary psoriatic lesion is an erythematous papule topped by a loosely adherent scale. Removing the silvery scales induces trauma to the underlying dilated capillaries and results in pinpoint bleeding at the site of the lesion, a finding known as the Auspitz sign.6 The scales “flake” off continuously and cause cracking, dryness and pain.

   The old “academic” definition, seen on board exams and in class, notes that the silvery scales with pinpoint bleeding is not the norm for there is a wide range of skin presentations. These presentations are not in a vacuum as the individual may have rubbed, scratched, soaked or warmed the area. Before presenting to your office, the patient may have used an array of topical agents and the area may have cleared and relapsed several times.

   Pruritus and burning are the main symptoms. Dogra and colleagues found pruritus to be present in 95 percent of their cases while burning was present in 15 percent.11 General measures for control of pruritus include keeping the skin cool and moisturized, and avoiding irritating fabrics. Ice packs may help stop the itching. Patients can apply a heavy moisturizing cream twice daily to help control scaling and pruritus. The podiatrist should prescribe specific pharmacologic measures on the basis of the patient’s history of psoriasis and overall medical condition.

What Factors Can Precipitate Or Exacerbate Psoriasis?

There are many “irritants,” both endogenous and exogenous, which affect psoriasis of the foot and lower legs. The endogenous irritants are varied. Some drugs may exacerbate or precipitate psoriasis. These include beta-adrenoceptor blockers, angiotensin-converting enzyme (ACE) inhibitors, non-steroidal anti-inflammatory drugs and anti-malarial drugs. Chloroquine (Aralen, Sanofi Aventis), lithium and mepacrine have been linked with severe deterioration of psoriasis.12 Systemic oral steroids will rapidly clear the plaques but may also worsen the flare and evolve into pustular psoriasis when the steroid use stops. Smoking and alcohol consumption may contribute to worsening psoriasis.

   Any object that comes in contact with the skin and rubs it or changes the “climate” of the skin can have an effect. The exogenous “irritants” that potentiate the skin response involve the Koebner phenomenon.13 The isomorphic response of Koebner occurs when skin lesions develop at the site of trauma and nowhere is there more trauma than the foot. Trauma can be the normal rubbing and scratching by the patient but it can also occur with orthotics, ankle foot orthotics, vascular hose or short and long leg casts. Therefore, any of our patients with psoriasis who need an orthotic or a cast are at potential risk for developing worsening skin conditions at that site. Other triggers that lead to the Koebner phenomenon are excoriation, sunburns and maceration.13

   As surgeons, we should be aware of this entity and warn our patients about its possible occurrence.14 In podiatry, we routinely use knives and sanding discs to remove thick calluses. If there is a patient with cracks on the rim of the heel, it is not unusual to debride the skin so a moisturizer can “heal” the fissures. However, in psoriasis, the mere “debriding” or “burring” of the skin equates to “trauma” of the skin. This can potentiate or increase scale production, and negatively impact the patient.

A Guide To Making A Differential Diagnosis

Psoriasis may occasionally resemble atopic dermatitis or eczema. However, it will usually be thicker, redder and more sharply demarcated than eczematous lesions. Psoriasis usually affects the extensor surfaces whereas eczema typically involves the flexor surfaces.15

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