Local symptoms of acne vulgaris may include pain, tenderness, and/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 connecting comedones and abscesses, without the presence of systemic symptoms, is known as acne conglobata. These severe forms of acne frequently heal with disfiguring scars. Additionally, acne vulgaris may have a psychological impact on any patient, regardless of the severity or the grade of the disease. 
Acne vulgaris is characterized by comedones, papules, pustules, and nodules in a sebaceous distribution (eg, face, upper chest, back). A comedone is a whitehead (closed comedone) or a blackhead (open comedone) without any clinical signs of inflammation. Papules and pustules are raised bumps with obvious inflammation. The face may be the only involved skin surface, but the chest, back, and upper arms are often involved.
In comedonal acne, patients develop open and closed comedones but may not develop inflammatory papules or nodules.
Mild acne is characterized by comedones and a few papulopustules. Note the image below.
Moderate acne has comedones, inflammatory papules, and pustules. Greater numbers of lesions are present than in milder inflammatory acne. Note the image below.
Nodulocystic acne is characterized by comedones, inflammatory lesions, and large nodules greater than 5 mm in diameter. Scarring is often evident. Note the image below.
The main underlying cause of acne is a genetic predisposition. In addition the following aggravating factors are recognized:
Cosmetic agents and hair pomades may worsen acne. 
Medications that can promote acne development include steroids, lithium, some antiepileptics, and iodides. 
Mechanical occlusion with headbands, shoulder pads, back packs, or under-wire bras can be aggravating factors. 
Excessive sunlight may either improve or flare acne. In any case, the ultraviolet exposure ages the skin.
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