Bacteria, especially Propionobacterium acnes, colonize the duct and produce lipases that break down sebaceous oils, liberating highly irritant fatty acids resulting in the earliest inflammatory phases of acne. Inibition of bacterial lipase production is a rationale for administration of antibiotics to patients with inflammatory acne. The lesions of acne vary from greasy red papules and pustules to cysts, nodules and scarring. Acne has both open and closed comedones. The closed comedones are a potential source of follicular rupture and deep inflammation and scarring.
Inflammatory acne is characterized by erythematous papules, nodules, and pustules.
Micro Histologically, the comedone forms as an expanding mass of lipids and keratin within the hair follicle, which becomes increasingly dilated. The follicular epithelium and sebaceous glands eventually atrophy. Extensive acute and chronic inflammation and scarring accompany follicular rupture. Systemic therapy, especially with tetracycline and erythromycin, are effective and act by interfering with the growth of the bacteria that produce the lipases.