A 31-year-old woman comes to the physician with a velvety skin rash in her axilla, as shown in the image below. Which of the following is the most likely cause of this patient's condition?

Question

A 31-year-old woman comes to the physician with a velvety skin rash in her axilla, as shown in the image below.  Which of the following is the most likely cause of this patient's condition?

Quizplus · Accepted Answer

This image shows the typical presentation of acanthosis nigricans (AN), which occurs most commonly in flexural areas. The most common locations are the axillae, posterior neck, and groin, but it may appear on other areas of the body such as the palms, soles, and oral mucosa & vermilion border. On physical examination, these lesions appear as hyperkeratotic, hyperpigmented plaques with a classic "velvety" texture. Skin tags (acrochordons) are pedunculated outgrowths of normal skin that are commonly present on regions affected by acanthosis nigricans. AN is associated with a number of diseases. Depending on the underlying condition, it is divided into benign and malignant forms. (Choices A and E) Hypersecretion of calcitonin (as in medullary thyroid cancer) and vitamin D resistance are not associated with AN. (Choice C) Hypersecretion of serotonin can occur with carcinoid tumors, including the gastrointestinal variety. However, excess serotonin itself does not cause AN. (Choice D) Testosterone unresponsiveness (androgen insensitivity syndrome, testicular feminization syndrome) develops due to a defect in testosterone receptors in peripheral tissues. Such patients are phenotypic females who present with primary amenorrhea. The uterus is absent and the vagina ends as a blind pouch, but breast development is normal due to the production of estrogen by aromatase. Educational objective: Acanthosis nigricans presents with thickening and hyperpigmentation of skin in the flexural areas. The lesions have a classic "velvety" texture. Acanthosis nigricans is commonly associated with insulin-resistant states (eg, diabetes mellitus, acromegaly, obesity) and gastrointestinal malignancies.

A 31-Year-Old Woman Comes to the Physician with a Velvety