A 50-year-old man comes to the office for evaluation of an itchy rash on his lower abdomen. The rash has been present for many months, and the patient is unable to obtain relief with moisturizers. He has no chronic medical conditions and takes no medications. On examination, the affected skin is noted to be thickened and dry; the rash is shown in the exhibit. The remainder of the examination reveals no abnormalities. What is the most likely cause of the patient's symptoms?

Question

A 50-year-old man comes to the office for evaluation of an itchy rash on his lower abdomen.  The rash has been present for many months, and the patient is unable to obtain relief with moisturizers.  He has no chronic medical conditions and takes no medications.  On examination, the affected skin is noted to be thickened and dry; the rash is shown in the exhibit.  The remainder of the examination reveals no abnormalities.  What is the most likely cause of the patient's symptoms?

Quizplus · Accepted Answer

11ec25c8_d375_756b_bc81_d92db920a967_MD0003_00 This patient has chronic allergic contact dermatitis (ACD) presenting with persistent itching and lichenification in the affected skin. ACD represents a type IV (cell-mediated) hypersensitivity reaction, with initial sensitization occurring within days of contact with the causative substance. On reexposure, the antigen is presented to sensitized lymphocytes, leading to inflammatory skin changes. Nickel (eg, belt buckles, watches, jewelry) is a common trigger for chronic ACD; corrosion of metal alloys by electrolytes in sweat releases soluble metal ions that trigger the hypersensitivity reaction. Nickel-induced ACD typically causes symptoms in characteristic locations, especially at the medial beltline (as in this patient), wrists, and earlobes. Other common allergens that can induce ACD include clothing dyes, topical medications, leather- and rubber-processing chemicals, and skin care products. Acute ACD results when the skin is reexposed to high levels of an allergen (eg, poison ivy) and manifests with intensely pruritic papules and plaques with erythema, vesicles, weeping, and crusting. In contrast, chronic, low-level exposure, as is typical in nickel allergy, leads to lichenification and pruritus. Most cases of ACD respond to application of topical corticosteroids and avoidance of the allergen. vesicles lichenification (Choice A) Chronic plaque psoriasis presents with pruritic erythematous plaques covered with silvery scales on multiple areas of the body. It is most common on extensor surfaces (eg, elbows, knees). This patient's lesion does not have silvery scales and is isolated to the abdomen. Chronic plaque psoriasis (Choice C) Infection with Trichophyton rubrum causes tinea corporis, which manifests as an expanding, scaly, annular plaque. This patient's lesion is not annular (ring shaped), and occurrence at the location of clothing fasteners is more suggestive of ACD. scaly, annular plaque (Choice D) Although scabies (Sarcoptes scabiei infestation) causes intense pruritus, the rash usually presents acutely with excoriated red papules and burrows, not a lichenified plaque. The distribution of rash usually involves >1 area (eg, hands, elbows, waist); rarely, scabies is localized to a single area. excoriated red papules (Choice E) Xerosis, or dry skin, is common in elderly persons and tends to occur when the environment is dry. Symptoms often occur on the lower extremities. Severe xerosis can evolve into an eczematous plaque. However, this patient's rash did not improve with moisturization, indicating a different etiology. Xerosis Educational objective: Nickel can cause chronic allergic contact dermatitis (type IV hypersensitivity) that is typically triggered by belt buckles, jewelry, or watches. Chronic, low-level nickel exposure can lead to itching and lichenification. Treatment includes topical corticosteroids and allergen avoidance. References: Diagnosis and management of contact dermatitis. (http://www.ncbi.nlm.nih.gov/pubmed/20672788)

A 50-Year-Old Man Comes to the Office for Evaluation of an Itchy