Treating Psoriasis In The Lower Extremity

In addition to reviewing the clinical presentation of psoriasis in the lower extremity, this author provides key insights on various topical medications ranging from corticosteroids and vitamin D analogs to retinoids and keratolytics. She also offers insights on systemic therapies that physicians may consider when the disability and disease severity warrant a more aggressive approach.

Psoriasis is a chronic, inflammatory, immune mediated skin disorder with extensive ongoing research dedicated to therapies that target specific pathways and immune mediators. Psoriasis occurs in 2.6 percent of the population in the United States.1 Given the numerous therapies available, choosing the optimal course of treatment can be overwhelming for the practitioner.

   Accordingly, let us take a closer look at key clinical considerations in managing plaque psoriasis and review the current and emerging topical medications.
The most common presentation is an erythematous plaque with silvery scales that is well defined geographically and symmetrical across the extremities. In the podiatric patient, the most common presentation is the palmar-plantar type, which typically presents on the volar surfaces of the hands and feet. These skin lesions may cause pain, pruritus, irritation, inflammation and fissuring. In addition to the clinical symptoms, patients may suffer from the psychological aspects of having a skin disease, which causes difficulty in performing activities of daily living as well as a feeling of being “contagious” to other people.

   Not only is psoriasis a disabling skin disease, it also predisposes the patient to systemic disorders collectively known as metabolic syndrome.2 Patients have a higher risk of developing comorbidities, such as diabetes, hypertension, hyperlipidemia and obesity, that may ultimately lead to heart disease. Accordingly, patients who have psoriasis have a greater risk of developing a myocardial infarction.3 Both the clinical (pain and deformity) and psychological (depression and anxiety) repercussions of the disease may lead to smoking, drug use, alcohol abuse and obesity that further contribute to the risk of developing cardiovascular disease.4

   The extent to which physicians can decrease the long-term effects of the metabolic syndrome is yet to be quantified in patients with psoriasis. For now, increasing quality of life and decreasing disability should be the ultimate goals.

What To Expect From The Patient Presentation

Patients will generally present with itchy, dry skin plantarly that may fissure, develop small pustules or be well defined erythematous patches. The pattern may include the whole plantar aspect, only the non-weightbearing surfaces or only the weightbearing surfaces. The scale can range from being limited to the skin lines and appearing as generalized xerosis to a fine silvery micaceous covering over a geographic plaque.

   Unfortunately, due to the prevalence of the scale, the most common misdiagnosis for plantar psoriasis is tinea pedis. In this case, patients will receive a prescription for a topical antifungal or purchase an over-the-counter (OTC) agent that will not work to their satisfaction. Patients will express their frustration with their current antifungal therapy and most likely not consider the possibility of psoriasis occurring on the feet.

   If the practitioner suspects psoriasis, there are several questions the physician and the patient can answer.

   • What is the state of the nails? Remember that psoriatic nails may look curiously similar to onychomycosis. In this case, also look at the fingernails for signs of pitting, onycholysis and trachyonychia (rough, sandpaper-like nails).

   • Ask patients if they have ever been diagnosed with psoriasis of the scalp or if there are any skin rashes anywhere else on the body (knees, elbows, gluteal fold). Most people do not correlate what is happening caudally to the skin rash plantarly.

   • Look at the palmar aspect of the hands. When plantar psoriasis occurs, it often manifests itself along with palmar skin disease. In comparison to the feet, the palmar skin may range from a mild xerosis to a more severe presentation with fissures and thickened scales.

   Simply performing a “scrape” or superficial shave of the scale will not assist the physician in diagnosing psoriasis or any other inflammatory skin disease. In the case of inflammatory skin diseases, the pathology report showing the presence or lack of a dermatophyte will only delay diagnosis and create more frustration for both practitioner and patient. Rather, a punch or incisional biopsy of a plaque will show the pathologist the whole histologic picture, which will aid in the diagnosis.

What You Should Know About Topical Therapy Options

After diagnosing psoriasis, most dermatologists will prescribe topical therapy as the first line of defense. The range and amount of these products are vast, and it is important to be comfortable with both the side effects and therapeutic effects when prescribing a treatment regimen for plantar psoriasis.

   When considering a topical treatment regimen, the physician should first consider the severity of the presentation (acute, subacute or chronic), how much of the patient’s activities of daily living are compromised, and the symptoms (i.e., pruritus, fissuring, dryness, irritation). These factors will dictate the choice and strength of the recommended products. Topical therapy is generally reserved for skin disease covering less than 5 percent of the body surface area (i.e., involvement of both plantar feet would be approximately 2 percent of the body surface area). Topical therapy can be quite effective if one uses the appropriate medications.

   The following are topical medications that one can use for plantar psoriasis.

   Topical corticosteroids (Class I to VI). Some common Class I (super potent) topical steroids are betamethasone, clobetasol (Clobex, Galderma) and halobetasol (Ultravate, Ranbaxy). These medications bind to the glucocorticoid receptors on cells that ultimately regulate gene transcription. This results in a reduction of the expression of common inflammatory modulators such as cytokines and histamine. Steroids cause not only an immune suppression but also have an anti-inflammatory effect.5

   Patients generally tolerate using the Class I steroids twice daily for one to two weeks. Using Class I steroids past that two-week period can result in the eventual manifestation of numerous and sometimes irreversible side effects such as skin thinning (atrophy), striae and decreased healing. In order to safely wean the patient off the Class I medications and prevent a rebound flare resulting from rapidly discontinuing medication use, I will start medication during the third week using a superpotent topical steroid and a mid-potency topical steroid on alternate days.

   A discussion about topical steroids is not complete without mentioning tachyphylaxis, a phenomenon that occurs with topical steroids and is the cause of much frustration to the psoriatic patient. Patients describe the phenomenon of using a previously beneficial topical that suddenly stops working as “hitting the wall” and then ask for another prescription to take its place with that topical steroid eventually succumbing to the same fate.6 It can be a vicious cycle and it is important to ask the patient specifically which medications he or she has tried and failed. This often results in the patient bringing in a large bag of once useful medications. However, it spares frustration for the physician and patient before starting on a new topical regimen.

   Vitamin D analogs. One often uses synthetic analogs of vitamin D alone or in conjunction with topical steroids in order to decrease inflammation and reduce plaque appearance. These medications do not have the same side effects as the topical steroids and do not seem to manifest in tachyphylaxis.7

   The current topicals on the market are calcipotriene (Dovonex) and calcitriol (Vectical, Galderma), which patients use twice daily. These topicals are more effective in combination with topical steroids than when used as monotherapies. An effective example of this is Taclonex (Leo Pharma), a stable combination of calcipotriene and betamethasone, which patients use once daily.

   Topical calcineurin inhibitors. Tacrolimus 0.01% ointment (Protopic, Astellas Pharma) inhibits various factors such as interleukin and tumor necrosis factor, which activate T-cells.8 Clinicians have used it as a treatment for various T-cell mediated diseases such as atopic dermatitis, vitiligo and dyshidrotic eczema. Its effect has been variable on plaque psoriasis and one should combine this with a preparation like salicylic acid in order to penetrate thickened scales.9

   Topical retinoids. Tazarotene 0.1% gel and 0.05% cream (Tazorac, Allergan) is a synthetic retinoid that normalizes the proliferation of keratinocytes and has an anti-inflammatory effect when patients use it once daily on plaques.10 When it comes to acne regimens, patients use it at night on the skin but can use retinoids in the morning as well when treating plantar psoriasis. In order to decrease the extremely irritating effects it has on the skin, the regimen can include using tazarotene every other day until tolerated. Patients apply tazarotene in conjunction with a topical steroid, applying petrolatum or another skin barrier cream around the plaques undergoing tazarotene treatment.11

   Keratolytics. Urea, salicylic acid and lactic acid creams and lotions help to remove excessive scales and soften keratin. This theoretically enhances the penetration of a topical steroid when patients use this in combination.

   Moisturizers. Over-the-counter emollients (Impruv lotion, Eucerin, Curel, CeraVe) or prescription counterparts (Neosalus, Quinnova Pharmaceuticals; Mimyx, Stiefel Labs/Glaxo Smith Kline; Atopiclair, Sinclair Pharma) can restore the function of the epidermal barrier, decrease transepidermal water loss and soothe the skin.12 When educating patients on the use of these preparations, it is best to tell them to apply the product within a few minutes of toweling off after bathing to have the best penetration. Overall, when patients use the emollients in conjunction with or after topical steroid therapy, they prolong remission and reduce flares.13

   Coal tar. These over-the-counter preparations are conventional and inexpensive treatments for psoriasis, but have the disadvantages of being greasy, staining clothing, smelling unpleasant and causing sensitivity to sunlight.14 In order to remedy this, the prescription Scytera foam (Promius Pharma) was developed to decrease the greasiness and odor of traditional preparations. Coal tar preparations reduce inflammation and pruritus, and have traditionally been a part of the Goëckerman regimen (coal tar plus UVB phototherapy).

   Anthralin (Zithranol-RR, Elorac). This preparation is an anthracycline, which reduces plaques by a mechanism of action yet to be determined. It is messy to apply and may stain clothing. One applies this as a short contact therapy in the office or long-term (24 hours) in an inpatient setting.15

Expert Pointers On Developing Effective Topical Regimens

If a patient is presenting to me with a new onset rash that is itchy, red and scaly, I am dealing with an acute flare and will generally recommend the following: a moisturizer such as Neosalus foam and a Class I topical corticosteroid (betamethasone). I may add to this regimen a vitamin D analog (calcipotriene) and a urea 40% preparation to descale. If the patient’s prescription plan will allow for it, I will not separate the Class I steroid and the vitamin D analog as two separate prescriptions. Instead, I will choose a combination therapy of the above components known as Taclonex, which patients use once daily.
The current trend in dermatology is to recommend or prescribe a moisturizer along with the topical corticosteroid. By restoring epidermal barrier function and decreasing transepidermal water loss, the prevailing thinking is that a moisturizer will decrease the need for the steroid (thus minimizing side effects) and decrease flares over the long term.

   As with any topical regimen, it is important to consider the following: patient education on use of the medications, a schedule of when to use the medications (morning versus evening application) and the vehicle one is using. In order to ensure patient adherence, I advocate using the simplest regimen but in a patient with an acute flare, that may not always be possible.

   For example, for a patient with a new onset rash that is itchy, red and scaly, I would recommend using the topical steroid and vitamin D analog at separate times during the day as they are incompatible when patients attempt to use them together. However, if I were able to prescribe the stable combination of those products, the patient would only use that preparation once daily and hopefully increase adherence.

   It is also important to remember that patients generally use Class I steroids twice daily for two weeks and then taper them during the third week with a Class III or IV in order to minimize the side effects of those potent medications. Remind patients that “more is not better” when it comes to the use of topical medications.

   One should teach patients the fingertip rule, namely measuring the amount of medication used from the distal crease to the tip of the index finger. Generally, patients use one fingertip of product on one plantar foot, one fingertip unit on the dorsum, etc. Two fingertip units equal approximately 1 g. Therefore, the physician can calculate the size of the tube needed between office visits.

   Lastly, one should factor into account the vehicle (ointment, cream, lotion, foam, etc.) when choosing a prescription medication. I consider the anatomical area to be treated (leg versus plantar foot), the severity of the skin rash and patient occupation. For example, I would typically choose a lotion for a leg but would consider a cream or ointment for the plantar foot. If the patient’s occupation is such that having an ointment on the plantar surface would be difficult, I would choose a foam or spray (i.e., something that would dry quickly and still be potent).

What About Systemic Therapy Options?

Topical preparations can be very effective for plaque psoriasis but there are cases in which these medications fail to provide improvement in the patient’s quality of life. Even though palmar-plantar psoriasis can affect less than 5 percent of body surface area in some cases, the disability and severity of the disease the patient experiences may warrant a more aggressive therapy.

   In these cases, one may explore systemic therapies such as cyclosporine and methotrexate. Clinicians may consider phototherapy using UVB or psoralen plus UVA radiation. Lastly, one can add the biologic preparations such as entanercept (Enbrel, Amgen/Pfizer), adalimumab (Humira, Abbott) ustekinumab (Stelara, Centocor Ortho Biotech) and infliximab (Remicade, Centocor Ortho Biotech) to the patient’s regimen and greatly improve clinical signs and symptoms.

   Even in a severe psoriatic case presentation, the topical therapies are still useful in conjunction to the systemic medications and biologics to provide local care, and may allow a decrease in the dosage of the systemic therapy physicians employ.15

Final Notes

Overall, topical treatment for psoriasis is extremely useful when one follows an effective regimen. The art of combining these medications in a useful manner takes time and experience on the physician’s part along with patience and adherence on the patient’s part.

   Dr. Vlahovic is an Associate Professor at the Temple University School of Podiatric Medicine. She is a Fellow of the American Professional Wound Care Association and is board certified by the American Board of Podiatric Surgery.

   Dr. Vlahovic pens a bimonthly blog for Podiatry Today. For more info, visit https://www.podiatrytoday.com/blogs/tracey-vlahovic-dpm.

References

1. Koo J. Population-based epidemiologic study of psoriasis with emphasis on quality of life assessment. Dermatol Clin 1996; 14(3):485-496.
2. Mallbris L, Ritchlin CT, Stahle M. Metabolic disorders in patients with psoriasis and psoriatic arthritis. Curr Rheumatol Rep. 2006; 8(5):355-363.
3. Kremers HM, McEvoy MT, Dann FJ, Gabriel SE. Heart disease in psoriasis. J Am Acad Dermatol. 2007; 57(2):347-354.
4. Wu Y, Mills D, Bala M. Psoriasis: Cardiovascular risk factors and other disease comorbidities. J Drugs Dermatol 2008; 7(4):373-377.
5. Ramsing DW, Agner T. Efficacy of topical corticosteroids on irritant skin reactions. Contact Dermatitis 1995; 32(5):293-297.
6. Singh S, Gupta A, Pandey SS, Singh G. Tachyphylaxis to histamine-induced wheal suppression by topical 0.05% clobetasol propionate in normal versus croton oil-induced dermatitis skin. Dermatology 1996; 193(2):121-123.
7. Kragballe K. Treatment of psoriasis with calcipotriol and other Vitamin D analogues. J Am Acad Dermatol 1992; 27(6 Pt 1):1001-1008.
8. Rivard J, Janiga J, Lim HW. Tacrolimus ointment 0.01% alone and in combination with medium-dose UVA1 in the treatment of palmar or plantar psoriasis. J Drugs Dermatol. 2006; 5(6):505-510.
9. Carroll CL, Clarke J, Camacho F, Balkrishnan R, Feldman SR. Topical tacrolimus ointment combined with 6% salicylic acid gel for plaque psoriasis treatment. Arch Dermatol. 2005; 141(1):43-6.
10. Duvic M, Nagpal S, Asano AT, Chandraratna RA. Molecular mechanisms of tazarotene action in psoriasis. J Am Acad Dermatol 1997; 37(2 Pt 3):S18-24.
11. Gollnick H, Menter A. Combination therapy with tazarotene plus a topical corticosteroid for the treatment of plaque psoriasis. Br J Dermatol 1999; 140(Suppl 54):18-23.
12. Proksch E. The role of emollients in the management of diseases with chronic dry skin. Skin Pharmacol Physiol 2008; 21(2):75-80.
13. Seite S, Khemis A, Rougier A, Ortonne JP. Emollient for maintenance therapy after topical corticotherapy in mild psoriasis. Exp Derm 2009; 18(12):1076-1078.
14. Sharma V, Kaur I, Kumar B. Calcipotriol versus coal tar: a prospective randomized study in stable psoriasis. Int J Dermatol 2003; 42(10):834-8.
15. Laws PM and Young HS. Topical treatments of psoriasis. Expert Opin Pharmacother 2010; 11(12):1999-2009.

   Editor’s note: For further reading, see “How To Handle Common Skin Dermatoses” in the September 2002 issue of Podiatry Today.