Overview of treatment principles for skin of color – Epidemiology, Pathogenesis, treatment and Therapy

INTRODUCTION

Treating acne in patients of color requires special consideration of the unique differences within this heterogeneous patient population. While pathogenesis, clinical presentation, and treatment are similar among all patients regardless of color, two important complications occur more frequently in ethnic skin postinflammatory hyperpigmentation (PIH) and scarring (1). Acne and its con-sequences may have a significant psychosocial impact, reducing quality of life (2). In fact, PIH and scarring are oftentimes the motivating factors for patients to seek medical attention in people of color (3).

Skin of color is traditionally classified as Fitzpatrick skin phototypes IV through VI and encompasses a spectrum of pigmented skin (4). People of color make up the majority of the world’s population (5) and are projected to represent half of the population in the United States by 2050 (6). This further highlights the importance of understanding management of acne in this patient population.

EPIDEMIOLOGY

Acne vulgaris is the most common dermatological condition among patients of color just as it is in the general population (7 12). It affects 40 to 50 million people nationwide (13). Most data regarding prevalence of acne in patients of color come from survey studies. In 1983, Halder et al. conducted a survey (of predominantly black and white private practices in Washington, D.C.) reporting that acne was the most common dermatologic diagnosis in both black (27.7%) and white (29.5%) patients. In 2007, Alexis et al. found similar results at the Skin of Color Center in New York City, with acne being the top diagnosis in both black (28.4%) and white (21.0%) patients seen. The incidence does not seem to differ in the Latino or Hispanic population (14). However, one study reported a higher prevalence of acne in Mexican-American indigent adolescents when compared with their white or African-American counterparts (15). Addi-tionally, a survey of Arab Americans documented acne as the most common self-reported diagnosis (16). In Singapore, a large study of 74,589 Asian patients was conducted, and similarly, acne was among the most common diagnoses observed there (17). A 2010 study by Perkins et al. (1) examined acne prevalence and subtypes among 2,895 Caucasian, Asian, continental Indian, and African-American women and noted somewhat different findings, reporting that African-American and Hispanic women showed a higher prevalence of clinical acne when compared to groups with lighter skin types.

PATHOGENESIS

The development of acne in skin of color is thought to occur by the same mechanisms as in Caucasians. Pathogenesis is multifactorial, including abnormal keratinization, excess sebum production, and infection with Propionibacterium acnes.

Structure and Function

Structural and functional differences among darkly pigmented skin types have important clinical implications for diagnosis and treatment of acne. One significant difference in the skin of darker-pigmented individuals is that it contains an increased amount of melanin. Melanin is derived from melanocytes located in the basal cell layer of the epidermis. These dendritic cells produce pigment via membrane-bound granules, known as melanosomes, in which melanin synthesis takes place (18). There is no major difference in the number of melanocytes between ethnic groups, but in darker skin types, melanosomes are more numerous, larger, and singly dispersed when compared with fair skin types. In addition to higher melanin content, melanosomes undergo a slower rate of degradation in darker skin (18). The variation in number and distribution of melanosomes may help to explain the differences seen with pigment disturbances associated with acne in patients of color. An exaggerated response of melanocytes to cutaneous injury (i.e., ultraviolet (UV) irradiation, irritating topical medications, or inflammatory medical conditions) (19) has also been observed in darker skin and may play a part in the development of dyschromias. Labile melanocytes seem to demonstrate increased melano-genesis or greater melanin release in the setting of inflammation or trauma (20,21).

A thicker, compact dermis containing many fragments of collagen fibrils and glycoprotein has also been described in darker skin types (22). Fibroblasts are reportedly larger and more numerous than those found in white skin, sug-gesting heightened activity (or reactivity), which may influence keloid and hypertrophic scar formation complications particularly common in individuals of African and Asian ancestry (22).

There is conflicting evidence on sebum production. Studies have shown no difference in sebum production between African-Americans and Caucasians (23,24), while others report that African-Americans have larger sebaceous glands, increased sebum secretion, and a greater pore count fraction (25). A positive correlation between darker pigmentation and the amount of skin surface lipids has been noted in Asian women (26). A recent study noted a negative correlation between pore size and skin lightness, that is, larger pores were associated with darker skin types. However, the authors did not find an associ-ation between pore size or pore count fraction and acne (1).

CLINICAL PRESENTATION

Acne typically manifests with characteristic lesions including comedones, pap-ules, pustules, nodules, and/or cysts affecting primarily the face, chest, and upper back. The physical examination should not only document the location and type of lesion but also assess for discoloration (hypo- or hyperpigmentation) and acne scarring (keloidal, hypertrophic, or atrophic). Clinical features that are of par-ticular importance in skin of color patients are PIH and scarring. Therefore, along with the classic lesions mentioned above, hyperpigmented macules or patches are often found at sites of previous acne eruption and may be present alongside active lesions (Fig. 2.3.1). Scars may take the form of atrophic (ice pick, boxcar, or rolling), hypertrophic, or keloidal scars (Fig. 2.3.2A, B) (27). It is common for dyschromia and scarring to remain after the acne lesions them-selves have resolved and thus serve as a primary complaint for many patients of color affected by acne. One study reported a high incidence of PIH, where 47%, 53%, and 65% of Asian, Hispanic, and black patients, respectively, were found to have acne and acne-related hyperpigmented macules (28). Nodulocystic acne is reportedly less common in blacks as compared with Caucasian or Hispanic patients (29).

Cultural Practices and Considerations

Cultural practices must also be taken into account when evaluating patients. Some common practices known to exacerbate acne in patients of color include the use of occlusive products such as cocoa butter, hair pomades (hair grease), or steroid-containing fade creams used by some populations to lighten the com-plexion. Pomade acne is a type of acne generally limited to patients of African descent and are to lesser degree seen in Hispanic patients who use lubricating products on the hair (30,31). Several cases have also been reported in East Africa in response to the practice of treating the face of children with petroleum jelly up to twice daily (32). The lesions typically consist of closed or open comedones on the forehead along the anterior hairline in a patient giving the history of pomade and/or oils used in the hair. This may be worsened when hairstyles allow direct contact on the face (i.e., bangs). Pomade acne is less prevalent today than pre-vious decades because of changes in hair care practices and the introduction of more sophisticated formulations of hair lubricants such as silicone-based prod-ucts (33,34).

HISTOPATHOLOGY

Even acne lesions in clinically mild cases may prove to be very inflamed and hyperactive. Noninflammatory lesions (i.e., comedones) and seemingly unin-volved skin beyond the lesion have shown marked inflammation on histo-pathology in black patients (35). This may contribute to the high prevalence of PIH and scarring in ethnic patients.

TREATMENT

Although treatment of acne vulgaris is similar among all skin types, the potential for disfiguring PIH and scarring as a result of acne in darker skin types warrants early and aggressive treatment. Nonetheless, balance between effective treatment of acne and the risk of inducing potential adverse reactions secondary to irritating preparations must be considered. Inappropriate selection and over-zealous use of treatments may lead to worsening inflammation and/or secondary irritant dermatitis with resultant dyspigmentation.

Topical Therapy

Retinoids

As in all acne patients, topical therapy is the first line in treatment of mild-to-moderate acne. Topical retinoids continue to be the leading choice in skin of color.

Retinoids are vitamin A derivatives, which have comedolytic effects as well as antikeratinization and anti-inflammatory properties. These agents also facilitate melanin dispersion and removal by increasing epidermal turnover (36), making topical retinoids particularly effective in the treatment of acne and associated PIH in pigmented skin (37 44). Adapalene, tazarotene, and tretinoin are frequently used and available in the United States. A common concern when using retinoids, however, is the potential risk of irritant dermatitis, which may lead to secondary PIH. To reduce this potential adverse effect, it is important to start treatment with lower doses and more tolerable formulations (i.e., creams vs. gels) (33). Microsphere formulations and aqueous-based gels are now available and tend to be well tolerated. Starting treatment with alternate-day dosing (three times weekly to every other night) and titrating up (once nightly) as tolerated is one approach commonly utilized.

Antimicrobials

Topical antimicrobials are often used in combination therapy in mild-to-moderate cases of inflammatory acne in skin of color patients. Macrolides and lincosamides, such as erythromycin and clindamycin, respectively, are effective in reducing P. acnes and inflammation. These antibiotic agents are often com-bined with topical benzoyl peroxide, an oxidizer of bacterial proteins, which reduces the development of bacterial resistance commonly seen when topical antibiotics are used as monotherapy. Available in concentrations ranging from 2.5% to 10% as lotions, creams, gels, masks, pads, foams, and cleansers, benzoyl peroxide is sometimes used as monotherapy. However, clinical studies have shown increased efficacy with combination therapy (45).

Like retinoids, benzoyl peroxide can be both drying and irritating, and therefore, it is important to minimize the risk of irritation by choosing lower concentrations and careful vehicle selection (33). In general, creams are better tolerated than gels, and aqueous gels better than alcohol-based gels. Patients should be informed that benzoyl peroxide can bleach hair and color fabrics.

Dapsone

Topical dapsone is one of the latest additions to the list of acne therapeutic agents. Approved for the treatment of acne, dapsone is classified as a sulfone. It carries anti-inflammatory and antimicrobial properties. Historically, systemic sulfones have shown positive effects on acne (46); however, systemic toxicities have limited its widespread use. A particularly problematic complication with use of systemic sulfones is dose-dependent hemolytic anemia in patients with glucose-6-phoshate dehydrogenase (G6PD) deficiency (47). G6PD deficiency commonly affects certain ethnic groups of African, Asian, Middle-Eastern, and Mediterranean ancestry, with an estimated prevalence in approximately 1 in 10 African-Americans in the United States (48,49).

Studies have shown that topical dapsone 5% gel is both safe and effective for the treatment of acne (50,51). When compared with oral dapsone, topical dapsone was found to have systemic exposures of 100-fold or less, even when given along with trimethoprim/sulfa-methoxazole (TMP/SMX) (52), which is known to increase systemic absorption of oral dapsone (53). Piette et al. conducted a study in which 64 ethnic patients with G6PD deficiency and acne vulgaris were treated with topical dapsone.

The authors demonstrated no clinical or laboratory evidence of drug-induced hemolytic anemia in this group (54). Investigators noted a slight decrease in hemoglobin concentration of 0.32 g/dL from baseline to two weeks during dapsone gel treatment. This was not accompanied by changes in other laboratory parameters (i.e., reticulocytes, haptoglobin, bilirubin, and lactate dehydrogenase levels). There was no apparent decrease in hemoglobin at 12 weeks as treatment continued. Thus, topical dapsone 5% gel imposes no significant risk of hemolytic anemia in patients with G6PD deficiency and is safe in all patients (54). Use of benzoyl peroxide along with topical dapsone may cause a temporary yellow or orange discoloration of the skin (55).

Other Topical Agents

Azelaic Acid

Topical azelaic acid is a naturally occurring dicarboxylic acid derivative, which has been reported to successfully reduce both inflammatory and noninflammatory acne lesions as well as decrease hyperpigmentation via its inhibitory effect on tyrosine (56,57). It has activity against P. acnes and Staphylococcus epidermidis in vitro, and antiproliferative effects against hyperactive and abnormal melanocytes (57,58). The latter property is beneficial in acne-associated PIH. Azelaic acid is formulated as a 20% cream for acne, its efficacy profile has been reported to be similar to that of tretinoin 0.05% cream, BPO 5% gel, erythromycin 2% ointment, and clinda-mycin 1% gel (59). Its low irritation potential, however, makes it well tolerated and suited for patients of color, especially those with sensitive skin (e.g., atopic der-matitis). The typical dose is azelaic acid 20% cream applied twice daily. More recently, azelaic 15% gel, indicated for rosacea, is increasingly used for acne vulgaris with good results (60,61).

Systemic Agents

Antimicrobials

Systemic agents are generally reserved for moderate-to-severe inflammatory acne and are often used in conjunction with topical therapy. Oral antibiotics are used in skin of color patients as in the general population. Commonly used oral antibiotics include the tetracyclines (e.g., tetracycline, doxycycline, minocycline) and the macrolides (e.g., erythromycin). Systemic antibiotics target P. acnes and reduce inflammation, improving acne and subsequently reducing the risk of PIH and scarring. Clinical studies have shown success when com-bining oral antibiotics with topical agents. Examples include minocycline along with tazarotene (62), or doxycycline plus adapalene (63).

Retinoids

The treatment of choice for severe or nodulocystic acne is oral isotretinoin (13- cis-retinoic acid). Although nodulocystic acne is reportedly less common in blacks as compared with Caucasian or Hispanic patients, some experts have proposed use of systemic retinoids in mild-to-moderate acne in skin of color as a way to avoid disfiguring PIH and acne scarring (33). When considering this systemic agent, the safety profile must be considered along with a careful examination of the risks and benefits. Of note, retinoids may cause adverse effects including teratogenicity, psychiatric disorders, hepatic toxicity, elevation in lipid profile, and mucocutaneous side effects. Therefore, careful patient selection and close monitoring are required.

Hormonal Therapy

Hormonal therapy for acne may be very effective in women even when androgen levels are normal. Several antiandrogenic therapies have been used to treat acne, including oral contraceptives (64) androgen receptor antagonists (e.g., spiron-olactone, flutamide, cyproterone acetate), finasteride, and corticosteroids. Thus, oral contraceptives, like norgestimate/ethinyl estradiol, Ortho Tri-Cyclen Lo® (Ortho-McNeil-Janssen Pharmaceuticals, Inc., New Jersey, U.S.), have been viable options in appropriately selected women who concurrently desire family-planning alternatives. It is important to consider that oral contraceptives may cause several side effects and can sometimes trigger the development of mel-asma (65), patchy hyperpigmentation predominantly on the face, which is especially common in patients of color.

Adjunctive Treatments

Intralesional Corticosteroids

Intralesional corticosteroids are often used as an adjunct for acutely inflamed nodules and cysts and offer a rapid response with marked improvement, gen-erally within 48 to 72 hours (66). Preparations of triamcinolone 10 mg/mL diluted with sterile water or lidocaine to concentrations of 2.5 to 5.0 mg/mL are commonly used (67,68). Concentrations as low as 0.63 mg/mL have also been reported to be effective in the treatment of nodulocystic acne (66). If keloidal or hypertrophic scarring is present, individual lesions may be injected with 10 to 20 mg/mL triamcinolone to flatten the lesions. This is generally repeated at two- to four-week intervals (33).

Rare complications of intralesional corticosteroid therapy include devel-opment of atrophy, telangiectasias, and hypopigmentation. The latter tends to be more visible in darkly pigmented individuals. Lower concentrations and wider intervals of treatment help to circumvent these potential effects. Suppression of the hypothalamic-pituitary-adrenal axis has been reported with repeated injec-tions or higher total doses (69,70).

Chemical Peels

Chemical peels are effective and safe in skin of color when limited to superficial peeling agents such as salicylic acid and glycolic acid (71,72). These agents induce epidermolysis and comedolysis (73,74). Salicylic acid and glycolic acid are often found in over-the-counter acne treatments in low concentrations. At higher concentrations, as chemical peels, they may aid in effective improvement of primary and secondary acne lesions, including PIH, as well as facilitates absorption of other topical agents (72). As a general rule, deeper peels are not used in darker skin types as the risk of complications is significantly greater. A series of peels with salicylic acid (20 30%) or glycolic acid (30 70%) performed at four-week intervals are usually performed for acne vulgaris. Concomitant use of topical retinoids may actually deepen the depth of the peel. For this reason, topical retinoids should be held for at least one week prior to treatment and may be resumed five to seven days after the peel. Some clinicians have suggested resuming all topical acne medications as soon as the skin ‘feels’ normal to the patient. Potential complications include scarring, hyperpigmentation, or hypo-pigmentation. Because of the risk of post-peel hyperpigmentation, pretreatment with hydroquinone 4% cream for one to two weeks before has been suggested as a way to minimize this risk in skin types IV to VI (71,72). Spot testing with the selected chemical peeling agent prior to full treatment is advisable in skin of color.

Microdermabrasion

Indications for microdermabrasion are similar to that of chemical peels and include acne, acne scarring, and hyperpigmentation. It is a noninvasive proce-dure that can be safely performed in all skin types (75), although acute skin inflammation, such as pustular acne, is a relative contraindication (76). Efficacy was noted in one study with 25 patients with grade II or III acne (77).

Fade Creams/Lightening Agents

Treatment of PIH is often incorporated into the acne treatment regimen and is best initiated after the acne itself is under control. Commonly used lightening agents include hydroquinone, azelaic acid, and kojic acid. Hydroquinone inhibits the action of tyrosinase, inhibiting melanin synthesis. Spot treatment with hydro-quinone 4% cream twice daily following the application of acne medications is recommended. Care must be taken to avoid inadvertent application to surrounding normal skin as a halo effect, with a noticeable hypopigmented ring surrounding the lesion may occur on the adjacent skin. This is generally transient. Cotton-swab application may help to minimize this effect.

Azelaic acid has activity against tyrosinase in addition to mild anti-inflammatory and comedolytic effects (57,60) and has also been effective in the treatment of melasma (78).

Sun protection is an important measure in treating skin of color patients with acne and PIH as UV exposure may exacerbate PIH. Sun protection factor (SPF) 15 or greater with both UVA and UVB protection and sun avoidance has been suggested as a necessary adjunct (79).

Laser Devices

Given the considerable risk for dyschromia and keloids, ablative resurfacing in darker skin types is generally not recommended. As many as 66% to 100% of patients with Fitzpatrick skin types IV to VI will develop some degree of hyperpigmentation, in contrast to up to 40% in skin types I to III (80). Ablative devices cause full thickness injury and include the carbon dioxide (CO2) and erbium:yttrium-aluminum-garnet (Er:YAG) lasers. Nonablative resurfacing is theoretically safer in darker skin types and is associated with less side effects and downtime. Few studies have examined the efficacy and safety of nonablative laser modalities in skin types IV to VI. A recent study by Mahmoud and colleagues (81) found significant improvement in facial acne scars in patients skin types IV to VI after five sessions with the fractionated erbium 1550-nm laser at monthly inter-vals. No difference was found between those treated with 10-mJ versus 40-mJ fluences at a constant treatment density. Other devices have reportedly shown some effect in pigmented skin, including the nonablative 1450-nm diode (82).

Common side effects include pain and hyperpigmentation. These effects seem to be more severe with increasing skin phototype type (greatest in skin type VI) (81). Other commonly used nonablative laser systems include the 1064-nm Q-switched Nd:YAG laser (83,84), 1320-nm Nd:YAG laser (85,86),1450-nm diode laser (86), and 1540-nm Er:Glass laser (87). It is important that no oral isotretinoin be used at least one year prior because there is a reportedly higher risk of abnormal postoperative healing and scarring (80).

Dermal Fillers

The concept of using injectable agents such as collagen, hyaluronic acid, and silicone to fill atrophic scarring has long been established (88 90). Of late, dermal fillers have gained popularity among various ethnic groups. Few studies have looked specifically at darker skin types however. Poly-L-lactic acid (PLLA) (91) has been reported to be effective and safe for treatment of macular atrophic scars. For some darker-skinned patients, injection site dyschromia may occur but generally resolves spontaneously within several weeks. No reports of keloid formation or hypertrophic scars post injection have been found.

A combination of procedures generally produces the best results. One case report noted satisfactory results in one Hispanic patient and one African-American patient where several procedures were performed including chemical peeling, punch grafting, subcision, dermal grafting, and dermabrasion (92).

Patient Education

Patient education is paramount to ensuring patient compliance with any treat-ment regimen. In patients of color, it is important to understand and be sensitive to differences in cultural practices and to educate patients as to potential exac-erbating factors such as those mentioned above. Questioning patients regarding their daily routine (i.e., cleansers, scrubs, astringents, and other over-the-counter topicals) is a great place to start. Gentle cleansers are best when prescribing any treatment regimen. Setting realistic expectations is essential. For example, informing patients of the risks of various medications, giving instructions in case they experience an adverse effect, or explaining that dark spots may take months to fade will aid in the patient’s compliance, outcome, and overall satisfaction.

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Jean-Paul Marat

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