A 35-year-old woman comes to the office due to a weeklong history of rash in the bilateral axilla. The rash is not painful and does not itch. Two weeks ago, the patient fractured her right ankle while jogging and has since ambulated with crutches. Medical history includes prediabetes. She smokes a pack of cigarettes a day. Her only medication is acetaminophen with codeine as needed for ankle pain. BMI is 33 kg/m². Vital signs are normal. On examination, many red papules and pustules are present in both axillae. There is no axillary lymphadenopathy or mass. The remainder of the skin examination is normal. Which of the following most likely contributed to this patient's skin condition?

Question

Quizplus · Accepted Answer

This patient has nonpruritic papules and pustules indicative of an acneiform rash. Whereas acne vulgaris typically occurs on the face and back, this patient's lesions are in the axillae. This presentation is most consistent with acne mechanica, which can occur anywhere pressure or friction is applied. In addition to crutches and other medical devices, common causes of acne mechanica include bra straps, turtlenecks, sports padding, helmets, and heavy backpacks. Recurrent mechanical pressure damages pilosebaceous follicles, leading to obstruction, comedone formation, and acneiform lesions. Eliminating the source of pressure is usually adequate to allow clearing of acne mechanica. (Choice A) Allergic contact dermatitis is a type IV hypersensitivity reaction to external allergens (eg, poison ivy, nickel). It manifests as erythema, swelling, vesicles, bullae, and lichenification (in chronic cases), typically with significant pruritus. The asymptomatic papules and pustules in this patient suggest a different etiology. erythema, swelling, vesicles, bullae (Choice B) Candidal intertrigo occurs in intertriginous areas where moisture and occlusion create an ideal environment for Candida albicans infection. However, the infection typically causes beefy red patches with satellite red papules or macules, not an acneiform eruption. red patches (Choice C) Irritant contact dermatitis is a nonimmunologic skin reaction to chemical agents (eg, solvents, detergents). It usually presents with erythema, edema, vesicles, bullae, and lichenification (in chronic cases), typically with a burning or stinging sensation. Irritant contact dermatitis typically affects exposed skin (eg, hands); axillary involvement is uncommon. lichenification (Choice E) Opiates can cause itching and urticaria through their effect on certain opioid receptors and through non-IgE mediated mast cell activation. Papules and pustules without itching are not characteristic. Educational objective: Acne mechanica is an acneiform eruption caused by pressure-related damage to pilosebaceous follicles. It can result from pressure from crutches, bra straps, turtlenecks, sports padding, helmets, and heavy backpacks. References: Inner thigh friction as a cause of acne mechanica. (http://www.ncbi.nlm.nih.gov/pubmed/30883890)

A 35-Year-Old Woman Comes to the Office Due to a Weeklong