The adrenal glands secrete higher amounts of DHEA-S during adrenarche (a stage of puberty), and this leads to an increase in sebum production. In a sebum-rich skin environment, the naturally occurring and largely commensal skin bacterium C. acnes readily grows and can cause inflammation within and around the follicle due to activation of the innate immune system. C. acnes triggers skin inflammation in acne by increasing the production of several pro-inflammatory chemical signals (such as IL-1α, IL-8, TNF-α, and LTB4); IL-1α is essential to comedo formation.C. acnes ability to bind and activate a class of immune system receptors known as toll-like receptors (TLRs), especially TLR2 and TLR4, is a core mechanism of acne-related skin inflammation. Activation of TLR2 and TLR4 by C. acnes leads to increased secretion of IL-1α, IL-8, and TNF-α. The release of these inflammatory signals attracts various immune cells to the hair follicle, including neutrophils, macrophages, and Th1 cells. IL-1α stimulates increased skin cell activity and reproduction, which, in turn, fuels comedo development. Furthermore, sebaceous gland cells produce more antimicrobial peptides, such as HBD1 and HBD2, in response to the binding of TLR2 and TLR4.C. acnes also provokes skin inflammation by altering the fatty composition of oily sebum. Oxidation of the lipid squalene by C. acnes is of particular importance. Squalene oxidation activates NF-κB (a protein complex) and consequently increases IL-1α levels. Additionally, squalene oxidation increases 5-lipoxygenase enzyme activity, which catalyzes the conversion of arachidonic acid to leukotriene B4 (LTB4).
The evaluation of a person with suspected acne should include taking a detailed medical history about a family history of acne, a review of medications taken, signs or symptoms of excessive production of androgen hormones, cortisol, and growth hormone. Comedones (blackheads and whiteheads) must be present to diagnose acne. In their absence, an appearance similar to that of acne would suggest a different skin disorder. Microcomedones (the precursor to blackheads and whiteheads) are not visible to the naked eye when inspecting the skin and require a microscope to be seen. Many features may indicate that a persons acne vulgaris is sensitive to hormonal influences. Historical and physical clues that may suggest hormone-sensitive acne include onset between ages 20 and 30; worsening the week before a womans period; acne lesions predominantly over the jawline and chin; and inflammatory/nodular acne lesions.Several scales exist to grade the severity of acne vulgaris, but disagreement persists about the ideal one for diagnostic use. Cooks acne grading scale uses photographs to grade severity from 0 to 8, with higher numbers representing more severe acne. This scale was the first to use a standardized photographic protocol to assess acne severity; since its creation in 1979, the scale has undergone several revisions. The Leeds acne grading technique counts acne lesions on the face, back, and chest and categorizes them as inflammatory or non-inflammatory. Leeds scores range from 0 (least severe) to 10 (most severe) though modified scales have a maximum score of 12.