**Question:** Pitted keratolysis affects -

A. Epidermis
B. Stratum corneum
C. Sebaceous glands
D. Apocrine glands

**Core Concept:** Pitted keratolysis, also known as keratolytic dermatitis or sweat gland acanthosis, is a skin condition characterized by the breakdown of the stratum corneum, leading to keratin layer dissolution and resulting in pitted, oily, and acne-like lesions. This condition is primarily caused by the overgrowth of Cutibacterium acnes in the apocrine glands, which results in the production of proteolytic enzymes that degrade the keratin in the stratum corneum.

**Why the Correct Answer is Right:** The correct answer, D (apocrine glands), is right because pitted keratolysis primarily affects the stratum corneum, which is a part of the epidermis. The stratum corneum is formed by the keratinocytes within the stratum corneum, and its breakdown is due to the overgrowth of Cutibacterium acnes. Apocrine glands are the primary site of Cutibacterium acnes colonization, leading to the overproduction of proteolytic enzymes that break down the keratin in the stratum corneum.

**Why Each Wrong Option is Incorrect:**

A (Epidermis) is incorrect because the stratum corneum, the site of pitted keratolysis, is a part of the epidermis. However, the condition itself occurs due to the overgrowth of Cutibacterium acnes in the apocrine glands.

B (Stratum corneum) is incorrect because the stratum corneum is a component of the epidermis, not a specific organ or structure affected by pitted keratolysis. The condition occurs in the stratum corneum due to Cutibacterium acnes colonization in the apocrine glands.

C (Sebaceous glands) is incorrect because sebaceous glands are not directly linked to pitted keratolysis. Apocrine glands are the primary site of Cutibacterium acnes colonization, leading to the overproduction of proteolytic enzymes that break down the stratum corneum. Sebaceous glands produce sebum, which is different from the apocrine glands that secrete sweat.

**Clinical Pearl:** Pitted keratolysis is a clinical entity to be considered when examining patients with acne-like lesions, especially in the axillae, groin, and axillary regions. Recognizing this condition can prevent unnecessary investigations and treatments for acne vulgaris, which is typically characterized by open comedones, papules, pustules, and nodules.