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Derm 101: A multi-part introductory series on Acne Vulgaris

The information and resources included below can help you educate your patients about Acne Vulgaris and how the disease is diagnosed and managed.


Part 1: Epidemiology, pathophysiology and clinical presentation

Acne is the most common skin condition in the United States, affecting well more than 50 million Americans each year. Approximately 85% of people experience some degree of acne between the ages of 12 and 24.[i] As the average age of puberty onset appears to be declining, it is not unusual now to see pre-adolescent acne starting as early as 7 to 11 years of age in otherwise healthy children.[ii]

On the other end of the spectrum, increasing rates of post-adolescent adult acne are also being reported, with an estimated 26% of women and 12% of men experiencing acne beyond age 25 and well into their 40’s and older. While considered a global disease, the highest acne prevalence rates were reported among Western Europeans, North Americans and southern Latin Americans.[iii]

Acne is a multifactorial inflammatory condition of the pilosebaceous unit, which consists of the hair follicle, hair shaft and sebaceous gland. The four key factors involved in acne pathogenesis include (1) altered follicular hyperkeratinization, (2) proliferation of Cutibacterium acnes (C. acnes; formerly Propionibacterium acnes, P. acnes), (3) increased sebum production, and (4) complex inflammatory mechanisms involving both innate and acquired immunity.[iv]

Several factors contribute to the severity and onset of acne flares, including genetic background, endocrine disorders, dietary and skin care habits and environmental factors. Severe acne is known to be associated with a family history, and several genetic factors have been identified—including the number, size, and activity of sebaceous glands, which all appear to be inherited.[v]

Endocrine disorders such as polycystic ovarian syndrome, hyperandrogenism, metabolic syndrome, hypercortisolism, and precocious puberty have been found to correlate with acne in all age groups, including adults.[vi]

Medications known to cause acne include androgens, glucocorticoids, phenytoin, lithium, and progesterones. While the connection between diet and acne remains controversial, data from several studies suggest that the consumption of skim milk, whey protein supplements, and/or high glycemic-index foods can exacerbate the condition.[vii] More recently, new interest in the roles of both skin and gut microbiomes in acne pathogenesis has led to increased investigation of these factors; however, their exact roles are not yet clear.[viii]

Acne is typically found in sites where sebaceous glands predominate, such as the face, shoulders, and upper trunk or torso.[ix] The classification of acne as inflammatory, comedonal, or mixed is based on the primary lesion types identified. Comedonal acne is characterized by the presence of open and/or closed comedones. Open comedones (a.k.a. “blackheads”) are the clinical manifestation of the accumulation of shed keratin within follicular openings. The black color of these lesions is secondary to melanin deposition and lipid oxidation within the debris. Closed comedones (a.k.a. “white heads”) clinically appear as small, skin-colored follicular papules with no associated erythema. Inflammatory acne is associated with papules, pustules, and nodules of varying severity.[x] Secondary changes due to acne include scarring, post-inflammatory erythema, and post-inflammatory pigmentation. Additionally, acne may cause significant psychological effects resulting in a negative quality of life and poor self-esteem. Studies report that patients with acne display higher rates of anxiety, unemployment, low self-worth and depression.[xi]

The severity of acne is based on the type, distribution, and number of lesions. Mild to moderate acne is often limited to the face and consists of mostly comedones, plus or minus a few inflammatory papules and/or pustules. Moderate to severe acne presents with more inflammatory lesions (pustules, nodules, or cysts) and typically affects the face, with or without involvement of the trunk and/or shoulders. In severe acne, both inflammatory and comedonal lesions, including nodules or cysts, are seen. Involvement of the trunk and shoulders is common, and scarring is more likely in these areas.[xii] Scarring can also occur in mild to moderate acne.[xiii]

The diagnosis of acne vulgaris is mostly clinical; however, a thorough patient history (including family history, medication and supplement use, diet, topical product application, skin care routine, psychiatric history, and review of systems) is important for identifying potential causative or exacerbating factors.[xiv] In the next installment of this two-part series, we’ll take a closer look at some of these factors as we discuss the initial evaluation, differential diagnoses and treatment.



[i]   Medscape, 2021. Acne Vulgaris. Available at: Accessed: Sep 2021.

[ii], 2020. Acne ages and stages; Acne in preteens. Available at: Accessed: Sep 2021.

[iii] Elemental, 2019. Why is Acne more prevalent than ever? Available at: Accessed: Sep 2021.

[iv] Epocrates Online, 2021. Acne Vulgaris. Available at: Accessed: Sep 2021

[v], 2020. Can acne be passed from parent to child? Available at: Accessed: Sep 2021.

[vi] Mayo Clinic Online, 2020. Acne Symptoms & Causes. Available at: Accessed: Sep 2021.

[vii] MDAcne, 2021. Do skim milk and dairy make acne worse? Available at: Accessed: Sep 2021.

[viii]            J Clin Med, 2019. Potential role of microbiomes in acne: a comprehensive review. Available at: Accessed: Sep 2021.

[ix] NIAMS, 2020. Acne. Available at: Accessed: Sep 2021.

[x]   Healthline, 2019. Types of Acne and how to treat them. Available at: Accessed: Sep 2021.

[xi] JAMA Dermatology, 2020. Development and initial validation of a multidimensional Acne grading system integrating primary lesions and secondary changes. Available at: Accessed: Sep 2021.

[xii], 2020. Systematic review of the epidemiology of Acne Vulgaris. Available at: Accessed: Sep 2021.

[xiii] J Drugs Dermatol, 2017. Prevalence and risk factors of Acne scarring among patients consulting dermatologists in the US. Available at: Accessed: Sep 2021.

[xiv] Am Fam Physician, 2019. Acne Vulgaris: diagnosis and treatment. Available at: Accessed: Sep 2021.

*Expert author(s), speaker(s) or contributor(s) where indicated are paid Galderma consultants.

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