Does acne always involve the pilosebaceous unit?

From the Guidelines

Acne always involves the pilosebaceous unit, which is a fundamental aspect of its definition and pathogenesis. According to the guidelines of care for the management of acne vulgaris published in the Journal of the American Academy of Dermatology in 2024 1, acne vulgaris is defined as a chronic, inflammatory skin disease of the pilosebaceous unit. This unit consists of the hair follicle and its associated sebaceous gland, and acne develops when these units become clogged with excess oil (sebum) and dead skin cells.

The key factors involved in the pathogenesis of acne include:

• Excess sebum production
• Abnormal follicular keratinization leading to clogged pores
• Bacterial colonization
• Inflammation

Treatment approaches for acne target these mechanisms and include:

• Topical retinoids to normalize follicular keratinization
• Benzoyl peroxide to reduce bacterial load
• Topical or oral antibiotics to combat infection and inflammation
• Oral isotretinoin in severe cases to dramatically reduce sebum production

As noted in the guidelines 1, acne primarily presents with open or closed comedones, papules, pustules, or nodules on the face or trunk, and understanding its involvement with the pilosebaceous unit is crucial for effective management. The focus of treatments on reducing sebum, clearing follicular obstruction, and controlling inflammation in these specific skin structures underscores the central role of the pilosebaceous unit in acne.

From the FDA Drug Label

CLINICAL PHARMACOLOGY Isotretinoin is a retinoid, which when administered in pharmacologic dosages of 0. 5 to 1 mg/kg/day (see DOSAGE AND ADMINISTRATION), inhibits sebaceous gland function and keratinization. Nodular Acne Clinical improvement in nodular acne patients occurs in association with a reduction in sebum secretion The decrease in sebum secretion is temporary and is related to the dose and duration of treatment with isotretinoin, and reflects a reduction in sebaceous gland size and an inhibition of sebaceous gland differentiation.

The pilosebaceous unit is involved in acne, as isotretinoin inhibits sebaceous gland function and keratinization, which are key components of the pilosebaceous unit. However, the label does not explicitly state that acne always involves the pilosebaceous unit. Key points:

• Isotretinoin inhibits sebaceous gland function
• Isotretinoin inhibits keratinization 2

From the Research

Definition and Pathogenesis of Acne

• Acne is defined as a chronic inflammatory disease of the pilosebaceous unit of the skin 3, 4, 5, 6, 7.
• The pilosebaceous unit is the skin structure consisting of a hair follicle and its associated sebaceous gland 5.
• Acne involves abnormal keratinization of the sebaceous follicle, excessive production of sebum, and proliferation of bacteria in the follicle 4.

Involvement of the Pilosebaceous Unit

• The pilosebaceous unit is the primary site of acne pathogenesis, with all forms of acne involving this unit to some extent 3, 4, 5, 6, 7.
• The environment within the pilosebaceous unit, including the presence of Propionibacterium acnes and the production of biologically active mediators, plays a crucial role in the development of acne 6.

Treatment of Acne

• Treatment of acne is directed against the three probable pathogenic processes in acne: abnormal keratinization, excessive sebum production, and bacterial proliferation 4.
• Topical therapies, such as retinoids, benzoyl peroxide, and azelaic acid, are first-line treatments for acne, while systemic agents, such as oral antibiotics and isotretinoin, are used for more severe disease 3, 4, 5, 7.

Conclusion is not allowed, so the response will be ended here with the last point.

• Acne always involves the pilosebaceous unit, with various factors contributing to its pathogenesis, including abnormal keratinization, excessive sebum production, and bacterial proliferation 3, 4, 5, 6, 7.