Based on the negative KOH and the nail pits, the FP made a diagnosis of plaque psoriasis. This condition can present in an annular pattern resembling tinea corporis. The combination of negative KOH and nail pits are enough to diagnose plaque psoriasis without a biopsy. Otherwise, a 4-mm punch biopsy of the area with erythema and scale would confirm the diagnosis.
Plaque psoriasis is typically treated using a mid- to high-potency topical steroid. Although repeated use of steroids in cases of atopic dermatitis can lead to skin atrophy, this is less common when treating psoriasis. If skin atrophy is still a concern, an alternative to topical steroids is a topical vitamin D preparation.
Vitamin D preparations are typically more expensive than steroids and require prior authorization, but there is one generic preparation (calcipotriene) that is more affordable than its brand-name counterparts. Another nonsystemic treatment to consider when treating plaque psoriasis without psoriatic arthritis is narrowband ultraviolet B therapy.
One risk factor for psoriasis is being overweight. In this case, the FP counseled the patient on weight loss. The FP then prescribed 0.1% triamcinolone ointment to be applied twice daily (especially after bathing).
At a follow-up appointment a month later, there was about 70% clearance of the lesions. For the stubborn areas, the FP prescribed a higher-potency steroid, 0.05% clobetasol ointment, to be applied twice daily. As the cost of clobetasol has risen over the past 2 years, alternatives that may be covered by insurance include augmented betamethasone and halobetasol.
Photos and text for Photo Rounds Friday courtesy of Richard P. Usatine, MD. This case was adapted from: Usatine R. Psoriasis. In: Usatine R, Smith M, Mayeaux EJ, et al, eds. Color Atlas of Family Medicine. 2nd ed. New York, NY: McGraw-Hill; 2013: 878-895.
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