Test your medicine knowledge with the MKSAP challenge, in partnership with the American College of Physicians.

A 33-year-old man is evaluated because of the recent appearance of stretch marks in his groin that extend to his thighs. He has a history of long-standing psoriasis that at times has involved much of his body, including his intertriginous areas. His topical treatments include tar-containing ointments, clobetasol propionate 0.05%, and calcipotriene 0.0005%; he has also undergone phototherapy. He is otherwise healthy.

On physical examination, scattered psoriasiform plaques are noted on the torso, elbows, knees, gluteal cleft, and scalp. There are pink, well-demarcated plaques in both axillae and in the inguinal folds. Purple striae extend from the inguinal creases onto the anterior thighs bilaterally. No moon facies or buffalo hump is present.

Which of the following treatments most likely resulted in this patient’s cutaneous changes?

A. Calcipotriene
B. Clobetasol propionate
C. Phototherapy
D. Tar-containing ointment

MKSAP Answer and Critique

The correct answer is B. Clobetasol propionate.

Clobetasol propionate 0.05% is an ultra–high-potency corticosteroid. Potential cutaneous complications associated with the use of topical corticosteroids include thinning of the skin, development of striae (stretch marks), development of purpura, pigmentary changes (hypo- or hyperpigmentation), acneiform eruptions, and increased risk of infections. Striae formation has been documented in 1% or more of patients using a mid-potency corticosteroid; the incidence may be higher with the use of more potent agents. The risk increases when corticosteroids are used for prolonged periods, are applied under occlusion, or are applied in skin folds where there is natural occlusion, as in this patient.

Calcipotriene, a vitamin D analog, inhibits proliferation of keratinocytes, normalizes keratinization, and inhibits accumulation of inflammatory cells (neutrophils and T-lymphocytes). Calcipotriene’s efficacy is comparable to that of medium-strength topical corticosteroids, but the drug is not associated with the cutaneous side effects seen in this patient.

Phototherapy induces T-lymphocyte apoptosis and therefore decreases proinflammatory cytokines. The most commonly reported side effects include photoaging, cataracts, and skin cancer. Severe cutaneous atrophy with striae formation is not a side effect of phototherapy.

Topical tar compounds are frequently used as corticosteroid-sparing drugs for patients with refractory psoriasis and are associated with excellent results when combined with ultraviolet B phototherapy. Coal tar products do not result in thinning of the skin.

Key Point

• Potential side effects of topical corticosteroids include development of striae and atrophy of the skin.

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