A 40-year-old man comes to the office due to a rash on his arms. The rash has been present for 3 weeks. The lesions are very itchy; he has applied several over-the-counter lotions, but they did not help. The patient has not participated in any unusual outdoor activity recently. He takes no medications on a regular basis. The patient has used intravenous illicit drugs in the past but not in the last 15 years. Vital signs are normal. Skin findings are shown in the exhibit. The remainder of the examination shows no abnormalities. Laboratory results are as follows: Which of the following is the most likely diagnosis?

Question

A 40-year-old man comes to the office due to a rash on his arms.  The rash has been present for 3 weeks.  The lesions are very itchy; he has applied several over-the-counter lotions, but they did not help.  The patient has not participated in any unusual outdoor activity recently.  He takes no medications on a regular basis.  The patient has used intravenous illicit drugs in the past but not in the last 15 years.  Vital signs are normal.  Skin findings are shown in the exhibit.  The remainder of the examination shows no abnormalities.  Laboratory results are as follows:  Which of the following is the most likely diagnosis?

Quizplus · Accepted Answer

11ec25c8_d37e_c44c_bc81_af2bb882fd35_MD0003_00 This patient has lichen planus (LP), an immunologically mediated skin disorder affecting middle-aged adults. LP typically develops symmetrically on the extremities, most commonly on the flexural surfaces of the wrists and ankles; the nails, oral mucous membranes, and genitalia can also be involved. The skin lesions are described by the 5 Ps: Pruritic, Purple/pink, Polygonal Papules and Plaques. They often have white, lacy markings known as Wickham striae and can form along lines of minor trauma (Köbner reaction). skin lesions Wickham striae The diagnosis of LP is based primarily on examination, but biopsy can be performed for confirmation. LP is often seen in association with hepatitis C; screening may be warranted in patients with a history of illicit drug use or elevated hepatic aminotransferase levels. A similar disorder can be seen with a number of common medications (eg, ACE inhibitors, thiazide diuretics). Although LP resolves spontaneously within 2 years, high-potency topical glucocorticoids (eg, betamethasone) are often used to accelerate healing and alleviate pruritus. (Choice A) Atopic dermatitis causes a pruritic rash affecting flexor surfaces but usually presents in childhood. Most patients have other atopic disorders (eg, allergic rhinitis, asthma). Atopic dermatitis (Choice B) Dermatitis herpetiformis causes an intensely pruritic rash on the elbows, back, knees, and buttocks. Lesions are typically herpetiform (ie, small, erythematous papules and vesicles); the purplish papules in this patient are not typical of dermatitis herpetiformis. Dermatitis herpetiformis (Choice C) Erythema multiforme presents with target-like plaques with central clearing that begin on the extensor surfaces of the distal extremities and spread centripetally; such plaques are not seen in this patient. Oral lesions and a febrile prodrome are also common. target-like plaques (Choice E) Tinea corporis presents with round or ovoid, annular plaques with a scaly border and central clearing, not the purple polygonal plaques seen in this patient. central clearing Educational objective: Lichen planus presents with pruritic, purple/pink, polygonal papules and plaques on the extremities, most commonly on the flexural surfaces of the wrists and ankles. Lesions may also occur on the oral mucosa, nails, and genitalia. Lichen planus is often associated with hepatitis C. Although this disorder resolves spontaneously, topical glucocorticoids can be used to accelerate healing and alleviate pruritus. References: Dermatologic manifestations of chronic hepatitis C infection. (http://www.ncbi.nlm.nih.gov/pubmed/28689593)

A 40-Year-Old Man Comes to the Office Due to a Rash