Acne vulgaris is a common chronic skin disease involving blockage and/or inflammation of pilosebaceous units (hair follicles and their accompanying sebaceous gland). Acne can present as noninflammatory lesions, inflammatory lesions, or a mixture of both, affecting mostly the face but also the back and chest.  See the image below.
Acne vulgaris has a multifactorial pathogenesis, of which the key factor is genetics.  Acne develops as a result of an interplay of the following four factors: (1) follicular epidermal hyperproliferation with subsequent plugging of the follicle, (2) excess sebum production, (3) the presence and activity of the commensal bacteria Propionibacterium acnes, and (4) inflammation. 
Signs and symptoms
Acne vulgaris is characterized by noninflammatory, open or closed comedones and by inflammatory papules, pustules, and nodules. Acne vulgaris typically affects the areas of skin with the densest population of sebaceous follicles (eg, face, upper chest, back). Local symptoms of acne vulgaris may include pain, tenderness, or erythema.
Systemic symptoms are most often absent in acne vulgaris. Severe acne with associated systemic signs and symptoms, such as fever, is referred to as acne fulminans. Severe acne, characterized by multiple comedones, without the presence of systemic symptoms, is known as acne conglobata. This severe form of acne frequently heals with disfiguring scars. Additionally, acne vulgaris may have a psychological impact on any patient, regardless of the severity or the grade of the disease. 
See Clinical Presentation for more detail.
Examination in patients with acne vulgaris includes the following features:
Comedonal acne: Presence of open and closed comedones but usually no inflammatory papules or nodules
Mild acne: Presence of comedones and a few papulopustules
Moderate acne: Presence of comedones, inflammatory papules, and pustules; a greater number of lesions are present than in milder inflammatory acne
Nodulocystic acne: Presence of comedones, inflammatory lesions, and large nodules greater than 5 mm in diameter; scarring is often evident
Acne vulgaris is a clinical diagnosis. However, laboratory testing may be indicated in the following situations:
Female patients with dysmenorrhea or hirsutism: Consider a hormonal evaluation with levels of total and/or free testosterone, dehydroepiandrosterone sulfate, luteinizing hormone, and follicle-stimulating hormone
Cases refractory to treatment or when improvement is not maintained: Culture skin lesions to rule out gram-negative folliculitis
See Workup for more detail.
Treatment of acne vulgaris should be directed toward the known pathogenic factors, including follicular hyperproliferation, excess sebum, P acnes, and inflammation. The most appropriate treatment is based on the grade and severity of the acne.
The following medications are used in the treatment of Propionibacterium acne vulgaris:
Retinoid-like agents (eg, topical tretinoin, adapalene, tazarotene, isotretinoin)
Antibiotics (eg, tetracycline, minocycline, doxycycline, trimethoprim/sulfamethoxazole, clindamycin, topical clindamycin, topical erythromycin, daptomycin)
Selective aldosterone antagonists (eg, spironolactone)
Estrogen/progestin combination oral contraceptive pills (eg, ethinyl estradiol, drospirenone, and levomefolate; ethinyl estradiol and norethindrone; ethinyl estradiol and norgestimate; ethinyl estradiol and drospirenone)
Acne products (eg, erythromycin and benzoyl peroxide, clindamycin and tretinoin, clindamycin and benzoyl peroxide, azelaic acid, benzoyl peroxide)
When a topical or systemic antibiotic is used, it should be used in conjunction with benzoyl peroxide or topical retinoid to reduce the emergence of resistance.
Diet therapy, such as a low-glycemic diet and avoidance of “junk foods,” has been suggested as a nonpharmacologic measure to manage acne vulgaris.
Procedural treatments for acne vulgaris include the following:
Manual extraction of comedones
Intralesional steroid injections
Superficial peels that use glycolic or salicylic acid
Acne vulgaris is characterized by noninflammatory, open or closed comedones and by inflammatory papules, pustules, and nodules. Acne vulgaris typically affects the areas of skin with the densest population of sebaceous follicles; these areas include the face, the upper part of the chest, and the back.
Acne vulgaris is the most common skin disease in the United States; it affects an estimated 80% of Americans at some time during their lives.  Twenty percent have severe acne, which can result in permanent physical and mental scarring.
Release of inflammatory mediators into the skin
Follicular hyperkeratinization with subsequent plugging of the follicle
Propionibacterium acnes follicular colonization
Excess sebum production
Research has shown that inflammatory responses actually occur before hyperkeratinization. Cytokines produced by CD4+ T cells and macrophages activate local endothelial cells to up-regulate inflammatory mediators such as vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), and human leukocyte antigen (HLA)–DR in the vessels around the pilosebaceous follicle. 
Follicular hyperkeratinization involves increased keratinocyte proliferation and decreased desquamation, leading to sebum- and keratin-filled microcomedones. 
P acnes is an anaerobic organism present in acne lesions. The presence of P acnes promotes inflammation through a variety of mechanisms. P acnes stimulates inflammation by producing proinflammatory mediators that diffuse through the follicle wall. Studies have shown that P acnes activates the toll-like receptor 2 on monocytes and neutrophils.  Activation of the toll-like receptor 2 then leads to the production of multiple proinflammatory cytokines, including interleukins 12 and 8 and tumor necrosis factor. Hypersensitivity to P acnes may also explain why some individuals develop inflammatory acne vulgaris while others do not. 
Excess sebum is another key factor in the development of acne vulgaris. Sebum production and excretion are regulated by a number of different hormones and mediators. In particular, androgen hormones promote sebum production and release.  The degree of comedonal acne in prepubertal girls correlates with circulating levels of the adrenal androgen dehydroepiandrosterone sulfate (DHEA-S). 
Numerous other mediators and receptors, including growth hormone and insulinlike growth factor, as well as peroxisome proliferator-activated receptors also regulate the sebaceous gland and may contribute to the development of acne. [12, 13] Furthermore, the sebaceous gland acts a neuroendocrine-inflammatory organ that is activated via corticotrophin-releasing hormones in response to stress and normal functions. 
Acne vulgaris affects 80% of Americans at some time during their lives.  Twenty percent have severe acne, which can result in permanent physical and mental scarring.
Persons of some races are affected more than others. Cystic acne is prevalent in the Mediterranean region from Spain to Iran. 
Acne is common in North American whites. African Americans have a higher prevalence of pomade acne, likely stemming from the use of hair pomades. Ethnicities with darker skin are also more prone to postinflammatory hyperpigmentation. 
During adolescence, acne vulgaris is more common in males than in females. In adulthood, acne vulgaris is more common in women than in men. 
Acne or acneform lesions, such as in neonatal cephalic pustulosis, may be present in the first few weeks and months of life, when a newborn is still under the influence of maternal hormones and when the androgen-producing portion of the adrenal gland is disproportionately large.  This neonatal acne tends to resolve spontaneously. However, some neonates may require therapy (eg, topical retinoids). 
Adolescent acne usually begins with the onset of puberty, when the gonads begin to produce and release more androgen hormone.
Acne is not limited to adolescence. Twelve percent of women and 5% of men at aged 25 years have acne. By age 45 years, 5% of both men and women still have acne. 
Acne may cause long-lasting and detrimental psychosocial and physical effects. It is associated with depression and anxiety, regardless of disease severity, although the psychological effects usually improve with treatment. Furthermore, acne may cause permanent scarring that is difficult to correct. 
In male patients, acne generally clears by early adulthood. Five percent of men still have acne at age 25 years. Female patients frequently have adult acne. Twelve percent of women still have acne at age 25 years. Five percent of women still have acne at age 45 years. 
The overall prognosis for persons with acne is good.
Patients should be instructed on their morning and evening treatment programs. Retinoid dermatitis may develop at approximately day 10 of therapy. Patients must be informed of this in advance so they will not consider this exfoliation an allergy. By skipping a day or 2 and restarting the program slowly, the skin can adapt to this irritation.
Prescriptions should be accompanied by a discussion of the potential adverse effects.
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