What is Acne and Its Forms
Acne vulgaris is a chronic inflammatory disease of the pilosebaceous follicles characterized by both non-inflammatory lesions (open and closed comedones) and inflammatory lesions (papules, pustules, and nodules/cysts). 1
Definition and Pathophysiology
Acne is a multifactorial inflammatory disease affecting the pilosebaceous units primarily on the face, neck, chest, and back. 1 The pathogenesis involves four key mechanisms:
- Follicular hyperkeratinization leading to plugged pores 1
- Increased sebum production driven by androgens 1, 2
- Colonization with Cutibacterium acnes (formerly Propionibacterium acnes), a Gram-positive anaerobic bacterium 1
- Complex inflammatory mechanisms involving both innate and acquired immunity 1
Additional contributing factors include neuroendocrine mechanisms, genetic predisposition, and environmental influences. 1, 2
Clinical Forms and Lesion Types
Non-Inflammatory Lesions
- Open comedones (blackheads): Dilated follicular openings filled with oxidized keratin and sebum 1
- Closed comedones (whiteheads): Obstructed follicles without visible opening 1
Inflammatory Lesions
- Papules: Small, raised, red bumps without visible fluid 1
- Pustules: Inflamed lesions containing visible pus 1
- Nodules (also called cysts): Deep, painful, solid lesions larger than 5mm 1
Severity Classification
The American Academy of Dermatology recommends using a 5-point ordinal scale (0-4: clear, almost clear, mild, moderate, severe) to quantify acne severity in clinical practice. 1, 3
Mild Acne
Moderate Acne
- Numerous comedones present 4
- Multiple papules and pustules 4
- Few small nodules may be present 4
- No significant scarring 4
Severe Acne
- Extensive papulopustular lesions 4
- Multiple nodules present 4
- Marked inflammation 4
- Scarring is present 4
Very Severe Acne
- Sinus tracts and grouped comedones 4
- Numerous deeply located nodules 4
- Severe inflammation and extensive scarring 4
Grading Systems
The Investigator Global Assessment (IGA) is the most commonly used grading system in the United States and demonstrates good agreement between clinician and patient ratings. 1, 3 However, no universal acne grading system can be recommended at this time, as descriptors require standardization and validation. 1
Other classification systems include the Leeds revised acne grading system, Global Acne Grading System, Global Acne Severity Scale, and Comprehensive Acne Severity Scale. 3
Clinical Assessment Considerations
When evaluating acne, assess the following:
- Predominant lesion type: comedones, papules, pustules, or nodules 3
- Lesion counts and distribution: number of lesions and anatomic sites affected 1
- Secondary changes: scarring, post-inflammatory erythema, or hyperpigmentation 3
- Disease extent and severity: overall involvement and impact 1
Epidemiology and Impact
Acne affects approximately 9.4% of the global population, with roughly 85% of individuals aged 12-24 years experiencing the condition. 1, 5 In the United States, over 50 million people have acne, with more than 5.1 million seeking medical treatment annually. 1
Quality of Life Impact
While acne causes no mortality, it produces significant physical and psychological morbidity comparable to chronic conditions like asthma, psoriasis, and arthritis. 1
- Permanent scarring affects up to 20% of teenagers 2
- Associated with poor self-image, depression, anxiety, and suicidal ideation 1, 5
- Impacts emotional functioning, social relationships, leisure activities, daily activities, sleep, school, and work 1, 3
- Increased risks of stigmatization and bullying 1, 3
- Higher unemployment rates in affected individuals 4
Common Pitfalls
Do not assume all acne-like lesions are acne vulgaris. Gram-negative folliculitis can mimic acne and may require microbiologic testing for proper diagnosis. 1 Additionally, certain endocrine disorders (particularly in prepubertal children or women with signs of hyperandrogenism) can present with acne and require hormonal evaluation. 1