Enlarged Pores and Sebaceous Hyperplasia

Bradley S. Bloom

ENLARGED PORES

BACKGROUND

Facial pores are a common cosmetic concern across genders and ethnicities. However, there is much confusion both among the lay public and in the medical literature surrounding the definition of “pores” and the etiology of visible pores. The term “skin pores” generally applies to the enlarged openings of pilosebaceous follicular units visible at the skin surface.¹,²

PRESENTATION

Skin pores may present as empty funnel-shaped structures or openings filled with cylindrical cornified plugs, which correspond to open comedones¹,³ (Figure 9.4.1).
Enlarged pores are most frequently found on the nose and medial cheeks.¹

FIGURE 9.4.1 Clinical image of enlarged pores on the forehead and glabella. The pores appear as empty funnel-shaped structures.

FIGURE 9.4.2 Optical coherence tomography of control skin of the lateral cheek (A) compared with the medial cheek (B) with more pronounced pores. (Images courtesy of Bradley S. Bloom, MD.)

DIAGNOSIS

Clinical Diagnosis

Commercially available skin analyzers have been used to quantify pore size and number. Kim et al. used one such device that classified morphological subtypes of pores: visible skin pores (size of 0.1-0.6 mm²), enlarged skin pores (size of 0.3-0.6 mm²), and blackhead-embedded skin pores.⁴ Commercially available optical coherence tomography imaging systems can be used to further quantify the characteristics of enlarged pores (Figure 9.4.2).

In vivo confocal laser scanning microscopy (CLSM) has been used to evaluate the architecture of facial pores. Under CLSM conspicuous pores demonstrate a central follicular opening surrounded by a thickened epidermis with a strongly undulated dermal-epidermal junction (DEJ).⁵,⁶ This undulating architecture of the DEJ
has been termed stalagmite-like (Figure 9.4.3) and is associated with larger hollows and uneven skin tone.⁵,⁷,⁸ Further CLSM studies have shown ethnic variation in pore size and stalagmite-like architecture, but the clinical significance has yet to fully be elucidated.⁶

FIGURE 9.4.3 Confocal image (A) of pore. Three-dimensional image (B) of a pore demonstrating the epidermaldermal junction around the hair follicle (dashed line) with the stalagmite-like structure. Asterisk (*) denotes dermal papillae. (Reprinted from Sugata K, Nishijima T, Kitahara T, Takema Y. Confocal laser microscopic imaging of conspicuous facial pores in vivo: relation between the appearance and the internal structure of skin. Skin Res Technol. 2008;14(2):208-212.)

Facial skin pores are present in all individuals, but the conspicuousness of these pores can vary as they are dynamic structures. Because of a lack of consensus on definition and pathophysiology, enlarged facial pores are a difficult condition to treat.

Histopathology

Histology of an enlarged pore is characterized as a hair follicle with a dilated infundibulum that is either empty or may have keratinaceous plug, which correlates with an open comedone.

PATHOGENESIS

The pathogenesis of enlarged facial pores is poorly understood but is clearly multifactorial, with both intrinsic and extrinsic factors playing important roles. Although there is no consensus agreement, the 3 major pathogenic factors include (1) increased sebum production, (2) increased hair follicle volume, and (3) decreased elasticity surrounding pores.¹,²,⁴,⁸,⁹,¹⁰ Additional factors that may play a role are genetic predisposition, recurrent acne, seborrhea, sex hormones, chronic ultraviolet light exposure, skin care regimen, topical cosmetics, and vitamin A deficiency.¹,³

Sebum Production

A positive correlation of sebum output and pore size has been well described.² This likely explains the finding that most enlarged pores are found on the nose and medial cheeks where casual sebum levels are higher compared with the lateral cheeks.¹ The relationship of pore size and sebum output is particularly well described in men where sebum production is driven by androgens such as testosterone. The relationship of sebum production and pore size is more complex
in women as the sebum production varies with the menstrual cycle. Roh et al. have demonstrated that sebum output and pore size increase during the ovulation phase of the menstrual cycle, which is believed to result from the effects of increased progesterone on sebaceous gland activity.¹,² Although the relationship of sebum output with pore size is clear, there are conflicting data on the relationship of gender and pore size.

Hair Size

It is hypothesized that hair thickness is an important factor in determining pore size. This hypothesis stems from a number of pieces of evidence. First, it has been demonstrated that pore volume correlates with the visual assessment of enlarged pores by fringe projection analysis using 2 and 3-dimensional images.¹¹ Second, pore volume is believed to be composed primarily of the hair follicle with or without the sebaceous gland.¹ Third, we know the volume of the dermal papilla correlates with hair follicle diameter and is androgen responsive. Thus, effective treatments for pore size will need to address the hair within the pore.

Loss of Elasticity

Loss of elasticity of the skin is associated with both chronological aging and photoaging.¹²,¹³ Several studies have demonstrated a correlation between pore size and loss of elasticity.⁴,⁸ It has also been shown that aged and photodamaged skin have decreased expression of microfibril-associated glycoprotein-1 (MAGP-1), which normally stabilizes the microfibril and elastin matrix network of the skin.¹⁰ This protein is decreased not only in the dermis but also around pores, and it has been hypothesized that age-related loss of MAGP-1 correlates with enlarged pores.¹⁰

TREATMENT

Although many treatment modalities have been proposed, there are relatively few clinical trials with enlarged pores as the primary investigative outcome. Treatments of enlarged pores are chosen to target the underlying causes and thus aim to decrease sebum output, decrease follicular size, and improve the elasticity of the skin.

Algorithm 9.4.1 outlines treatment options for enlarged pores.

Medical

Topical Retinoids

Topical retinoids are vitamin A analogs that are frequently used in the treatment of acne vulgaris, photoaging, and facial roughness.¹⁴,¹⁵ The mechanism by which topical retinoids improve acne is through normalization of corneocyte cohesion and follicular keratinization, which loosens existing pilosebaceous unit obstruction and prevents further obstruction. A number of trials have demonstrated improvement in the appearance of enlarged pores with topical retinoids.¹⁶,¹⁷ The use of topical retinoids can be limited by dose-related skin irritation. It is important to note we cannot conclude that topical retinoids directly improve enlarged pores because we are unable to differentiate the effects of normalized keratinization and corneocyte cohesion of the pilosebaceous units. Topical retinoids have also been shown to treat photoaging through increased collagen synthesis and normalization of elastic tissue, which may contribute to improving the appearance of enlarged pores.¹⁴

Cosmetic

Chemical Peels

A variety of chemical peel formulations are available for the treatment of photoaging and acne. Several studies have demonstrated improvement of enlarged pores with chemical peels. In one study using a series of glycolic acid peels every 2 weeks for a total of 5 treatments, over 70% of participants demonstrated improvement in enlarged pores.¹⁸ Another study using a series of chemical peels with a proprietary formulation of α-hydroxy acids and vitamin C demonstrated significant improvement in pore size reduction.¹⁹ Although several chemical peel formulations have been shown to improve the appearance of enlarged pores, it is unclear if this can be reliably reproduced.

Injectable Neurotoxin

Increasing evidence indicates that intradermal injections of botulinum toxin type A (BoNT-A) can decrease sebum
production and improve pore size.²⁰,²¹,²² Using a sebometer, Rose et al. demonstrated that intradermal injection of BoNT-A resulted in a statistically significant (P<.001, t test) reduction in sebum production at 1 week and 1, 2, and 3 months following injection.²¹ Shah has also demonstrated the use of intradermal BoNT-A to reduce sebum production and facial pore size.²⁰ Although further clinical trials are required to validate this technique, it has become increasingly popular. Further investigation into the dose response is also warranted.

ALGORITHM 9.4.1 Treatment of enlarged pores. EBD, energy-based devices; IPL, intense pulsed light; Nd:YAG, neodymium:yttrium aluminum garnet; RF, radiofrequency. (Courtesy of Macrene Alexiades, MD, PhD.)

The mechanism of action by which intradermal BoNT-A reduces sebum production and pore size remains unclear. However, it is hypothesized that inhibition of the release of acetylcholine and its cotransmitters (eg, substance P) leads to decreased sebum production. This hypothesis is supported by evidence that acetylcholine signaling has a significant role in human sebaceous gland biology and sebum production.²¹,²³ It is hypothesized that the appearance of enlarged pores is improved through a combination of reduced sebum output and neuromodulatory effects on the arrector pili muscles.²⁰

It is critical to understand that the technique of injection for this off-label indication, sometimes referred to as “microdroplet,” requires precise placement of small amounts of BoNT-A in the dermis. One potential complication of this technique is temporary paralysis of underlying skeletal muscles. This is particularly when treating the cheeks and perioral skin. Shah has suggested a technique of inserting a 30-gauge or smaller needle at a 75° angle for injection to facilitate intradermal placement. He has also suggested that extrusion of the injected toxin from adjacent pores may be an indicator of correct depth.²⁰,²¹ Success of the intradermal BoNT-A technique is dependent on reproducible delivery of BoNT-A at precisely controlled depths and precise dosage. We may see new microdroplet delivery systems introduced over time to address this issue.

Lasers, Light-Based Devices, and Energy-Based Devices

Lasers and light- and energy-based devices (EBD) have received significant attention in the treatment of acne and enlarged pores, but as previously discussed, there are relatively few clinical trials with reduction in pore size the primary investigative outcome. Several excellent resources review the energy device treatment of acne that are beyond the scope of this chapter.²⁴

Intense Pulsed Light. Intense pulsed light (IPL) devices have be demonstrated to be effective in the improvement of photodamaged skin and visible improvement of pore size.²⁵ Bitter et al. used an IPL source (Vasculight, ESC/Sharplan, Norwood, Mass, USA) to treat 49 subjects with varying degrees of photodamage. Four or more (average 4.94) full-face treatments were performed at 3-week intervals using cut-off filters of 550 or 570 nm for all treatments. Subjects were asked to rate the severity of fine wrinkles, texture, laxity, irregular pigmentation, pore size, telangiectasias, facial erythema, and facial flushing.²⁵ Sixty-seven percent of subjects reported at least a 50% improvement in the appearance of their pores.²⁵

Sadick et al.²⁶ also demonstrated improvement in the appearance of pores with a combination device using
synchronous intense pulsed optical and conducting bipolar radiofrequency (RF) energy. One hundred and eight subjects received 5 full-face treatments at 3-week intervals using this combination device (Aurora SR, Syneron, Yokneam, Israel).²⁶ Double-blinded physicians performed photographic evaluation and reported a 65.1% improvement in the appearance of pores.

It is important to note that in both studies, improvement of pore size was assessed using subjective evaluations. The proposed mechanisms of action for improved pore size with IPL treatments include reduction in hair follicle size or hair removal resulting in decreased pore volume as well as improved skin elasticity and neocollagenesis.¹

Nonablative Lasers

Nonablative Laser: 1064-nm Nd:YAG. The use of nonablative near-infrared lasers in skin rejuvenation is well established, and these devices have been shown to stimulate neocollagenesis.²⁷,²⁸ Many wavelengths of light have been investigated for rejuvenation, but the 1064-nm neodymium-doped yttrium aluminum garnet (Nd:YAG) laser with nanosecond and microsecond pulse durations has received much attention.

Koh et al.²⁹ used a nonablative microsecond 1064-nm Nd:YAG laser system (Vantage, Brisbane, CA, USA) to treat 12 Korean subjects for rejuvenation of photodamaged skin. The subjects received a series of 5 full-face treatments at 3- to 6-week intervals with the Nd:YAG laser using a painting technique (fluence 13-14 J/cm², pulse duration 0.3 ms, spot size 5 mm, repetition rate 7 pulses/s).²⁹ Improvement was assessed using subject and investigator clinical evaluations. Photography, Mexameter, Sebumeter, and Visiometer analysis of silicone replicas of the left cheek were also used in assessment of improvement. In this trial the investigators noted a statistically significant improvement in elasticity, texture, and enlarged pores following the third and fourth treatments compared with baseline.²⁹ However, this same improvement in pore size did not reach statistical significance using subject self-assessments. It is hypothesized that the improvement is seen as a result of improved skin elasticity and neocollagenesis.

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