Acne vulgaris is a common chronic inflammatory disease of the hair follicles and sebaceous glands during adolescence, frequently occurring on the face and often accompanied by seborrhea. The condition is self-limiting and typically resolves by adulthood.

bubble_chart Etiology

The occurrence of acne is the result of multiple factors working together, primarily related to increased sebum production, hyperkeratinization of the follicular opening, and the proliferation of Propionibacterium acnes within the follicle, along with certain genetic factors. The development of sebaceous glands is regulated by androgens. During adolescence, increased androgen production enlarges the sebaceous glands and boosts sebum secretion, which is then excreted through the follicular opening to the skin surface. In acne patients, abnormal keratinization of the follicular epithelium prevents normal shedding of epithelial cells, narrowing the follicular opening and causing sebum to accumulate rather than flow freely, leading to acne formation. Normally, the follicle contains Propionibacterium acnes, Malassezia furfur, and Staphylococcus epidermidis. When sebum stagnates within the follicle, these bacteria proliferate. The enzymes produced by Propionibacterium acnes break down sebum, generating free fatty acids that are a major cause of inflammatory reactions in the follicle. Propionibacterium acnes also produces some low-molecular-weight peptides that act as chemoattractants for neutrophils. The hydrolytic enzymes released by these neutrophils cause the follicular wall to develop exudation or even rupture, allowing the contents of the follicle to enter the surrounding dermal tissue. This results in a range of clinical manifestations, from inflammatory papules to cystic lesions.

It often occurs during adolescence, with females typically developing symptoms earlier than males, usually half a year to one year before the onset of menstruation. The lesions primarily appear on the face, especially the forehead, cheeks, and chin, followed by the chest, back, and shoulders. Initially, it manifests as acne, including whitehead acne and blackhead acne, both containing keratin and sebum. Whitehead acne, also known as closed comedones, presents as flesh-colored papules, about the size of a pinhead, with an inconspicuous follicular opening, making it difficult to squeeze out the sebaceous plug. Blackhead acne, also called open comedones, features a clearly enlarged pore at the center of the papule, with the sebaceous plug blocking the follicular opening. The black appearance is due to the oxidation of sebum and melanin, and the yellowish-white sebaceous plug can be more easily extruded.

Acne can progress to inflammatory papules, pustules, nodules, or cysts. Inflammatory papules are usually the size of a grain of rice to a mung bean. Some may develop secondary化脓感染 due to severe inflammation or manual picking, forming pustules or abscesses with a pus-filled center. Nodules appear purplish-red or dark red, either raised hemispherically above the skin or deeper and only palpable, gradually resolving over time. Cysts are flesh-colored or dark red, hemispherical, and raised above the skin, with a fluctuant sensation upon touch. Nodular acne and cystic acne are more common in males and are less likely to subside. When secondary bacterial infection occurs, the lesions become significantly red, swollen, and tender. Healing may leave behind atrophic or hypertrophic scars. Clinically, several types of lesions often coexist, with one or two being predominant.

Additionally, there is a special type of acne called acne conglobata, which is more common in young and middle-aged males, frequently affecting the back, buttocks, and cheeks. The onset is slow, starting with acne, papules, pustules, and cysts, which gradually merge to form predominantly cystic lesions. These cysts may become spindle-shaped or large, irregular patches, soft and fluctuant to the touch. Upon rupture, they form sinuses or fistulas, interconnected beneath the skin, leaving behind atrophic or hypertrophic scars on the surface. The condition has a prolonged course, with fluctuating severity, often taking several years to subside, leaving noticeable scars after healing.

bubble_chart Diagnosis

The patients are mostly young men and women, with primary lesions such as acne, papules, or pustules, commonly occurring in areas with abundant sebaceous glands like the face, upper chest, and back, symmetrically distributed, making diagnosis straightforward.

bubble_chart Treatment Measures

The principle is to remove oil, dissolve keratin, sterilize, and reduce inflammation.

1. Patients should avoid consuming irritating foods, frequently wash the affected area with warm water, and use sulfur-containing soap for better results. Advise patients to refrain from squeezing the lesions with their hands, avoid using cosmetics with high oil content, and avoid long-term use of medications containing iodides or bromides.
2. For acne patients primarily presenting with acne, papules, or pustules, topical treatments alone may suffice. Commonly used agents include sulfur and resorcinol-containing preparations, such as compound sulfur lotion, which have oil-removing and keratolytic effects; antibiotic preparations like 1% lincomycin liniment or 2–4% erythromycin alcohol; and 5–10% benzoyl peroxide gel or cream. Benzoyl peroxide has antibacterial and sebum-suppressing effects, significantly reducing Propionibacterium acnes counts and inhibiting acne formation. Topical application may cause grade I skin irritation, and use should be discontinued if significant erythema occurs. A 0.05–0.1% tretinoin cream has keratolytic and exfoliating effects, making acne plugs easier to remove and sebum plugs easier to expel. Topical application may also cause some skin irritation, such as erythema or peeling. The above topical treatments should be used alone or in combination based on the condition of the lesions.
3. For patients with severe acne primarily presenting with nodules, cystic lesions, or numerous and highly inflamed lesions, the following methods may be considered in addition to topical treatment:
   1. Oral antibiotics: Tetracyclines are commonly used, such as tetracycline at an initial dose of 1.0 g/day, reduced to 0.25–0.5 g/day after significant inflammation subsides, and continued for several weeks. Minocycline, due to its lipophilic properties, penetrates sebaceous glands more effectively, resulting in stronger antibacterial effects. The dosage is 100 mg/day, reduced to 50 mg/day for maintenance after inflammation subsides. Doxycycline is administered at 200 mg/day initially, then reduced to 100 mg/day for maintenance. Tetracyclines are photosensitizing, and use should be discontinued immediately if photodermatitis occurs. Other antibiotics, such as erythromycin at 0.5 g/day, may also be used.
   2. Isotretinoin capsules: These strongly inhibit sebaceous gland secretion and also suppress Propionibacterium acnes. The initial oral dose is 0.5–1.0 mg/kg/day, typically 30–60 mg/day, reduced for maintenance after significant improvement. Treatment lasts 3–4 months. Side effects may include dry lips, skin peeling, alopecia areata, and elevated blood lipids. Use with caution in patients with impaired liver or kidney function. This medication is teratogenic, so contraception is required for men and women of childbearing age during treatment, and pregnancy should be avoided for six months after discontinuation.
   3. Corticosteroids: For severe nodular, cystic, or conglobate acne, oral prednisone at 30–40 mg/day may be effective. For individual lesions, triamcinolone acetonide suspension (10 mg/mL) or prednisolone suspension (5 mg/mL) mixed with a small amount of 2% procaine can be injected into nodular or cystic lesions once weekly for 3–4 weeks. Long-acting corticosteroid preparations may also be injected into lesions once monthly.
4. Endocrine therapy: Sebaceous gland development is regulated by androgens, so anti-androgenic drugs can treat acne. However, this therapy may disrupt endocrine balance and is generally not recommended. For female patients with acne worsening before menstruation, 10 mg of progesterone may be injected intramuscularly one week before menstruation. For severe female acne patients, diethylstilbestrol may be taken at 1 mg/day starting on the 14th day of the menstrual cycle for two weeks.
5. Physical therapy: Liquid nitrogen cryospray or spot application is suitable for nodular or cystic acne. Specialized acne extractors may be used to remove acne contents. Facial masks, including medicated masks and gypsum masks, may also be employed.
6. Chinese medicine refers to this disease as "acne." The treatment principle involves ventilating the lungs and clearing heat. Internally, Loquat Lung-Clearing Decoction can be taken (composed of Tangshen, loquat leaf, Coptis Rhizome, White Mulberry Root-Bark, Phellodendron Bark, and Liquorice Root). Externally, apply Inverted Powder (Rhubarb Rhizoma and sulfur) mixed with cool water.

bubble_chart Differentiation

It should be differentiated from the following diseases:

1. Rosacea: Mostly occurs in middle age, commonly affecting the central part of the face, with manifestations including diffuse erythema, papules, pustules, and telangiectasia.
2. Occupational acne: Frequently seen in workers regularly exposed to tar, engine oil, petroleum, paraffin, etc., presenting with acne-like eruptions that are densely distributed and may be accompanied by follicular keratosis. Besides the face, it can also appear on the back of the hands, forearms, and other areas exposed to mineral oils.
3. Lupus miliaris disseminatus faciei: The lesions are brownish-yellow or dark red hemispherical or slightly flattened papules, symmetrically distributed on the eyelids, nasolabial folds, and cheeks, often merging into a ridge-like formation on the lower eyelids.