Presentations of Cutaneous Disease in Various Skin Pigmentations: Acne Vulgaris - Comedonal Acne

Abstract

Description

Acne vulgaris is a common inflammatory skin condition of the pilosebaceous unit in adolescents and young adults and is primarily characterized by the presence of open and closed comedones. In patients of various skin pigmentations, skin-colored comedones may be difficult to appreciate and lead to incorrect or delayed diagnosis of acne. To aid in the identification of acne vulgaris in patients of various skin pigmentations, we present comedonal acne in different skin types and commonly encountered differential diagnoses. With its significant volume and burden of disease, acne vulgaris should be correctly identified in various skin pigmentations by primary care clinicians for the initiation of appropriate management.

Introduction

Acne vulgaris is a chronic inflammatory skin condition involving the pilosebaceous unit.¹ The development of an acneiform lesion begins with the formation of comedones from normal pores.¹ This process is driven by androgenic stimulation associated with puberty, which gives rise to increased sebum and keratin production within pilosebaceous units. Colonization with the bacterium Cutibacterium acnes (formerly Propionibacterium acnes) is additionally associated with the pathogenesis. The result is impaction of the follicular opening.¹ Subsequent activation of the inflammatory cascade induces advancement to inflammatory papules, pustules, nodules, and cysts, which may promote discoloration, scars, and keloids.¹ Acne is classified by severity (eg, mild, moderate, or severe) and the predominant lesion type (eg, comedonal, papulopustular, nodulocystic, or conglobate).¹ This article discusses the comedonal presentation of acne and how it manifests in various skin pigmentations.

Comedones are non-inflammatory acne lesions. There are 2 types of comedones, open and closed, which differ by the visibility of the follicular opening. Accumulated keratin and sebum within closed pores result in closed comedones, colloquially referred to as whiteheads.² By contrast, open follicles expose the keratinaceous material to air, which undergoes oxidation and accumulation of melanin granules. This leads to darker-appearing open comedones, or blackheads.² Both comedones are non-inflammatory and exhibit the same color as the surrounding skin.

Acne vulgaris commonly affects adolescents and young adults, with 85% of affected individuals aged 12–24 years old, but is observed frequently from ages 5 to 44.^1,3 The classic distribution is on the face and trunk as these anatomic locations have increased populations of pilosebaceous units.¹ Several exacerbating factors have been studied, including diet, smoking, stress, and genetics. The pathogenesis of acne remains the same across skin types; however, differences in skin structure and anatomy can produce varying presentations that clinicians must recognize.

Skin pigmentation varies among individuals and across ethnic groups. The Fitzpatrick scale was created to describe the spectrum of skin tones based on the physical characteristics of tanning and burning in response to ultraviolet light exposure. A visual depiction of this scale is found in Figure 1, which illustrates the classification of Fitzpatrick skin types I–VI. Additional background information on the Fitzpatrick scale and a description of the classification are discussed separately.⁴

Figure 1.

The Fitzpatrick scale provides a classification system for an individual’s skin type based on that individual’s ability to burn and/or tan when exposed to ultraviolet light. It is frequently, though incorrectly, used to approximate the degree of skin pigmentation.

This presentation of clinical images received IRB exemption.

Case Presentation

Figure 2 shows a 16-year-old male with Fitzpatrick type I (always burns, never tans) skin. This image demonstrates comedonal acne on the midline upper back. There are several closed comedones, which are small, skin-colored papules (raised, <1 cm) without a visible follicular opening. There are also scattered open comedones, demonstrated as small, skin-colored papules, with a dilated central follicular opening containing a dark-brown follicular plug. While comedones are the predominant lesion type, erythematous papules and pustules (raised, <1 cm) are also seen. The dark brown keratinaceous material within the open comedones is easily contrasted against the pallor of the surrounding skin.

Figure 2.

Fitzpatrick I (always burns, never tans): (A) Scattered open and closed comedones are seen on the midline upper back of an adolescent male. The color of each comedone is the same as the surrounding skin. (B) Closed comedones (solid arrows) are small, raised, skin-colored lesions without a visible follicular opening. Open comedones (open arrows) are small, raised, skin-colored lesions with dilated follicular openings. They are filled with oxidized keratin that appears brown-to-black.

Figure 3 demonstrates non-inflammatory acne in a 12-year-old female with Fitzpatrick type II (mostly burns, rarely tans) skin. Several scattered open and closed comedones are found on the forehead. The comedonal lesions are the same color as the surrounding skin. In lighter skin types, open comedones are more easily visualized as the color of the oxidized keratin differs from the background skin.

Figure 3.

Fitzpatrick II (mostly burns, rarely tans): Scattered open and closed comedones are seen on the forehead of an adolescent female. The closed comedones are the same color as the surrounding skin. The open comedones, in contrast, are more easily visible as open follicles with oxidized keratin.

Figure 4 shows comedones in Fitzpatrick III (sometimes burns, often tans) type skin. Figure 4A illustrates comedones on the temple and cheek of a 20-year-old female. In this image, closed comedones are predominant. Figure 4B has many comedones on the lateral cheek and alar nose. The superior and malar cheeks exhibit predominantly closed macrocomedones. Macrocomedones are larger comedones ranging from 2–3 mm in size. A few lesions superior to the nasolabial fold are inflammatory in nature with surrounding erythema. In Fitzpatrick III skin, open comedones are more difficult to appreciate as the keratinaceous material appears more similar in color to the surrounding skin.

Figure 4.

Fitzpatrick III (sometimes burns, often tans): (A) On the right temple and cheek of a young adult female, predominantly closed, with some open, comedones are seen. Coincidental erythematous papules are also seen on the lateral cheek. (B) Macrocomedones are seen on the right lateral nose and medial cheek of a young adult female. These are larger comedones ranging from 2–3 mm. Incidental erythematous papules and violaceous macules, at the sites of prior lesions, are also seen on the right lateral cheek.

Figure 5 exhibits comedonal acne in Fitzpatrick IV (rarely burns, mostly tans) type skin. The forehead of a 14-year-old female shows scattered open and closed comedones. Open comedones with dark keratin are increasingly difficult to see. Some closed comedones on the forehead are advancing to inflammatory papules. This is evident by mild pink erythema that is often more subtle than erythema seen in lighter Fitzpatrick skin types.

Figure 5.

Fitzpatrick IV (rarely burns, mostly tans): Scattered comedones are seen on the forehead of an adolescent female. There is a predominance of closed comedones (solid arrow) with scattered open comedones (open arrow). Macrocomedones are also seen.

Figure 6 demonstrates non-inflammatory acne in a 14-year-old female with Fitzpatrick V (almost never burns, always tans) type skin. There are scattered open and closed comedones located on the forehead and cheeks. The dark keratinaceous material within open comedones is less contrasted with the surrounding skin, making them more challenging to appreciate. On the forehead and cheeks, scattered hyperpigmented macules (flat, <1 cm) indicate post-inflammatory changes from previous acne lesions.

Figure 6.

Fitzpatrick V (almost never burns, always tans): Acne vulgaris of an adolescent female is seen. On the forehead and temple, there are scattered closed comedones (black solid arrows). Some open comedones are present on the cheeks (black open arrows). Also, an inflammatory papule is seen (white solid arrow). Pustules are papules (raised, <1 cm) with tips containing white, purulent fluid. One pustule is seen (white open arrow). The associated erythema of inflammatory acne is visible but not pronounced, masked by the skin’s natural pigmentation.

Table 1 illustrates the differential diagnosis of comedonal acne, including keratosis pilaris, milia, and sebaceous hyperplasia. Figure 7 shows an example of keratosis pilaris rubra faceii in an 8-year-old female. This clinically presents with follicular-based skin-colored papules on the face that may mimic closed comedones. Clinical involvement of the proximal extremities, background erythema, and a history of atopic disease favor this variant of keratosis pilaris.⁵ Milia are 1–2 mm papules that are non-follicular, have a light whitish color, and are usually distributed periorbitally as in a 14-year-old female in Figure 8.⁶ Sebaceous hyperplasia, demonstrated in a 49-year-old female in Figure 9, may also mimic closed comedones, but these occur on the forehead and cheeks of older adults and have an umbilicated center.⁶

Table 1.

A Summary of Common Differential Diagnoses for Comedonal Acne Vulgaris.

Condition	Predominant ages	Morphology	Color	Distribution
Comedonal acne	Adolescents and young adults	Closed and open comedones	Skin-colored	Face, chest, and back (sebaceous)
Keratosis pilaris	Children through young adults	Papules	Skin-colored to erythematous	Face (rubra pilaris), dorsal arms, lateral thighs, back
Milial cysts	All ages	Papules	Skin-colored, with white top	Face (periorbital)
Sebaceous hyperplasia	Middle-aged and older adults	Umbilicated papules	Skin-colored, with orange-yellow hue	Face

Figure 7.

Fitzpatrick II (mostly burns, rarely tans): On the cheek of a young girl, follicularly-based skin-colored to erythematous papules are seen, consistent with keratosis pilaris rubra faceii. These papules are commonly mistaken as the comedones of acne vulgaris.

Figure 8.

Fitzpatrick IV (rarely burns, mostly tans): A white-topped papule (raised <1 cm), consistent with a milial cyst, is seen on the right medial lower eyelid margin of an adolescent female. These papules are commonly mistaken as comedones of acne vulgaris.

Figure 9.

Fitzpatrick I (always burns, never tans): Several yellow-orange papules (raised, <1 cm) with a central pore are seen on the left temple of a middle-aged female. These are sebaceous hyperplasia, which are often mistaken for comedones in acne vulgaris.

Discussion

Acne can present in patients as open and closed comedones, papules, pustules, nodules, and cysts.¹ Comedonal acne presents predominantly with non-inflammatory open and closed comedones. These are not associated with inflammatory signs, such as erythema, and thus are skin-colored.¹ Histologically, comedones show little evidence of inflammation.¹ Inflammatory acneiform lesions, however, do often exhibit erythema, induration, and pain, and they reveal lymphocytic infiltration on histopathology.¹ Interestingly, comedonal acne patients with darker Fitzpatrick skin types exhibit a different histologic pattern. In a study of African American female patients, comedonal lesions clinically graded as mild showed marked inflammation histologically.⁷ This finding may contribute to an increased prevalence of hyperpigmented post-acne lesions in patients of darker skin color.⁷

Comedonal acne presents differently across the spectrum of Fitzpatrick skin types. It is important that clinicians are equipped to identify this condition. Because comedones are skin-colored lesions, they may be difficult to distinguish from the surrounding skin. Visualizing the skin from various angles and using a hand-held light source (eg, side lighting) may help identify comedones by highlighting their raised nature. This is especially useful in patients with darkly pigmented skin, as the shadows cast from illuminating comedones can appear more faintly. Additionally, open comedones can present with lower contrast in darker Fitzpatrick skin types. Closer visual inspection allows for these lesions to be distinguished from surrounding skin.

Sequelae of acne, namely post-inflammatory hyperpigmentation and scarring, occur more frequently in patients with skin of color. Post-inflammatory hyperpigmentation and permanent scarring may occur even in cases of clinically mild-appearing acne.⁸ Emotional distress is another negative result of acne and acne-related scarring.^1,8 Early recognition of acne, especially at its mildest stages, can minimize its potentially long-lasting sequelae.

Conclusion

Equipped with the knowledge to accurately diagnose comedonal acne vulgaris, physicians will be able to provide excellent care to patients of all skin types.

Funding Statement

This research was supported (in whole or in part) by HCA Healthcare and/or an HCA Healthcare-affiliated entity.