Acne: Understanding What's Happening On the Skin -

Michael H. Berkson, M.D.

What’s happening on the skin in acne is a direct extension of what’s happening microscopically in the skin. Having some insight as to what’s going on at the surface can help one to understand how the various acne treatments work as well as which particular types of treatment might be most applicable to a given situation.

Types of Acne Lesions ( Morphology)

There are four main types of lesions that can appear during the course of acne. These various types can appear in isolation in any given person, or more commonly as a mixture of different types.

Comedones typically first appear early in the course of acne and can persist throughout. There are two types of comedones, closed comedones, or whiteheads, and open comedones, or blackheads. Comedones tend to be most visible on the face. Comedones are not associated with visible inflammation, unlike the other three main categories of acne lesions.

Papules, commonly referred to as pimples, are seen on the skin as red bumps and correspond to areas of localized inflammation deep within the pilosebaceous follicle. Papules tend to become more numerous as the acne becomes more developed.

Pustules, also referred to as pimples, are the superficial version of the papule. In this case the inflammatory reaction resides higher in the follicle, and the collection of white blood cells ( pus) can be seen at the surface. Many times there is a mixture of papules and pustules. This is referred to as papulopustular acne.

Nodules present as localized red swellings that are deep in the skin and may be painful. They represent areas of intense inflammation surrounding the ruptured follicle. The acne nodule is the most severe of the four main types of acne lesions and has the greatest propensity to scar.

Complications of Acne

To follow are the most common after effects that can result as acne lesions resolve. These are much more commonly seen in association with inflammatory than comedonal acne.

Post inflammatory erythema refers to persistent redness at the site of a resolved papule pustule or nodule. It is caused by residual inflammation and recedes with time.

Post inflammatory hyperpigmentation (PIH) are dark spots or blemishes that are left at the site of prior inflammatory lesions. These result from over activity of the melanocytes ( pigment producing cells) that are stimulated by the inflammatory response in and around the follicle. PIH tends to be more persistent and bothersome in people of color whose melanocytes tend to be more sensitive to stimulation. PIH blemishes are often referred to as scars but they are not. They do fade over time and also respond to treatment with topical medications such as retinoids (Retin-A and Differin) and bleaching creams.

Scarring represents textural changes in the skin that are usually permanent and the result of alterations in collagen in the second layer of skin (dermis) It is not known why some people are more prone to scaring than others, but for some, there appears to be a genetic predisposition. In general, the more inflammatory nodular acne is more likely to scar, yet there are some who have papular acne that scars significantly.

There are two broad categories of acne scars, atrophic and hypertrophic. Atrophic scars are indentations or depressions in the skin and usually occur on the face. There are several variants of atrophic scars that have descriptive names based on their appearance. Hypertrophic scars are the opposite of atrophic. They present as firm, raised red to flesh colored plaques and are most commonly seen on the shoulders back and chest

Cysts can occasionally develop as a result of inflammatory acne. A cyst is a balloon-like structure that forms deep in the skin. It has a well defined lining and is filled with a material called keratin. Most of what are referred to as acne cysts are actually nodules. Cysts are permanent structures whereas nodules are temporary pockets of intense inflammation that do not have a lining.

Location of Acne (Distribution)

Acne can occur anywhere on the body where there are pilosebaceous follicles. These specialized hair follicles are most numerous on the face, neck, scalp, back, shoulders, and chest, which are the most common locations for acne. Teenage acne most commonly occurs on the face and, to a lesser extent, on the trunk. Men are more likely to have significant truncal involvement than woman. Adult acne, which affects women more often than men, tends to favor the lower face and jawline.

Acne Severity

For the purposes of this discussion, acne severity has to do with the degree to which the acne is, or has the potential to significantly alter one’s appearance in the short or long term, as well as whether the acne is having a negative impact on one’s mental health and/or psychosocial functioning. There are qualitative, quantitative and subjective aspects of acne severity.

The qualitative component refers to the types of acne lesions and the presence or absence of or potential for complications such as scarring. In general, the more deep seated inflammatory lesions such as papules, and especially nodules, are associated with more severe acne. The presence of scarring is certainly indicative of severe acne. The number of acne lesions is also a factor in determining acne severity. In general, the more numerous the lesions, the more severe the case. Although uncommon, one can have severe acne that is primarily comedonal.

The subjective element refers to whether or not the acne is adversely impacting the person’s mental health including their self image and ability to function in social settings. There is no question that acne can worsen or even trigger episodes of anxiety and depression in some individuals. It is possible for a person to have mild acne on the qualitative and quantitative scale, yet be markedly impaired psychologically and psychosocially as a result of their skin condition. In this situation, the acne is severely impacting the individual and they deserve aggressive treatment as well as psychological support

Timeline and Course of Acne

Acne is an almost ubiquitous condition in that 90% of people are affected at some point during their lives. In most, acne follows a rather predictable course. That said, acne can be capricious in that it can come and go at will.

Acne usually first manifests during the preteen years, although sometimes it starts much earlier or later. With the onset of adrenarche, the skin takes on a more oily appearance as the sebaceous glands begin producing sebum. The development of comedones, usually in the T zone area of the face, follows soon thereafter. Over time, the inflammatory lesions of acne begin to appear among the comedones, initially in the form of papules and pustules. At this stage, the development of acne often begins to occur on the trunk. This may be followed by inflammatory nodules in some people. Typically, acne peaks during the late teen years and then gradually abates.

Adult acne, arbitrarily defined as acne occurring in people age 25 and older, is becoming increasingly common. It is estimated that up to 30% of women and a lesser percentage of men have acne in their mid 20’s and sometimes into their 30’s and 40’s. Adult acne is a continuation of teen acne in 75% of cases and first begins during the adult years in the remainder. It is unclear why adult acne is on the increase but it is a very real phenomenon. In women it often tends to have a clear cut hormonal component and flare ups leading up to the menstrual period are commonly reported. Stress is probably an aggravating factor in some as stress can alter the physiology and hormones that help drive acne.

The next four articles in this series will focus on the medical treatment of acne.

References:

Acne vulgaris: pathogenesis, treatment, and needs assessment. Knutsen-Larson S, Dawson AL, Dunnick CA, Dellavalle RP. Dermatol Clin. 2012 Jan;30(1):99-106.

Acne vulgaris. Williams HC, Dellavalle RP, Garner S. Lancet. 2012 Jan 28;379(9813):361-72.

The interaction between acne vulgaris and the psyche. Baldwin HE. Cutis. 2002 Aug;70(2):133-9.

The prevalence of acne in adults 20 years and older. Collier CN, Harper JC, Cafardi, JA, et al. J Am Acad Dermatol 2008; 58(1): 56-59.

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