What are the different types of acne?

Theacne is an inflammatory disease of the pilosebaceous follicle. Very common, it primarily affects teenagers. However, adults can also be affected by this condition.

Acne manifests itself through the emergence of inflammatory or non-inflammatory pimples. Generally, these appear on the face, but they can also be found on the body (back, chest, buttocks, etc.).

Acne is a complex disease ofmultifactorial origin. The pathophysiology of acne includes, among other things, 3 key elements:

• An overproduction of sebum (hyperseborrhea) :

Sebum is a complex mixture of lipids synthesized by the sebaceous glands located in the dermis. Under normal conditions, it is evenly distributed across the skin, providing protection.

In the case of acne, we observe ahypersecretion of sebum(also known as hyperseborrhea) at the level of the pilosebaceous follicles. The sebum clogs the pores, which are the openings of the sebaceous glands on the skin's surface. This fat-rich environment is conducive to the proliferation of the bacteria responsible for acne,Cutibacterium acnes(formerly Propionibacterium acnes), which primarily feeds on sebum. This bacteria secretes pro-inflammatory substances that cause inflammation and the formation of pimples.

• An abnormal follicular keratinization:

In the case of acne-prone skin, we observe a abnormal thickening of the epidermal cells (hyperkeratinization) which prevents the elimination of sebum. This leads to an obstruction of the follicular canal and the formation of comedones or blackheads.

• A bacterial colonization:

As previously mentioned, there is a bacterium responsible for acne: it is Cutibacterium acnes. This bacterium secretes pro-inflammatory substances that cause acne.

Recent research has proven that there is a imbalance of the skin microbiota (dysbiosis) responsible for the proliferation of Cutibacterium acnes. Through immune mechanisms, this bacterium leads to hyperkeratinization of the pilosebaceous follicles.

Note : Acne is multifactorial in origin, meaning there are several factors that can contribute to its onset such asdiet, stress, or the use of unsuitable cosmetic products.

Acne is a very common disease, affecting not only teenagers but also adults. Its pathophysiology includes hyperseborrhea, abnormal follicular keratinization, and a proliferation of Cutibacterium acnes within the pilosebaceous unit.

There is not just one, but several types of acne. Among them, we find:

• Retentional Acne:

This type of acne is primarily observed in adolescents, as it results from an overproduction of sebum. Indeed, under hormonal influence, the sebaceous glands produce an excessive amount of sebum. This sebum clogs the openings of the hair follicles, thus forming acne lesions. In retentional acne, two types of lesions are generally observed: the microcysts (closed comedones) and the blackheads (open comedones).

• Inflammatory Acne:

Generally, inflammatory acne follows retentional acne (hence the importance of acting early before inflammation). Indeed, the overproduction of sebum promotes the proliferation of Cutibacterium acnes which secretes pro-inflammatory substances. If the inflammation is superficial, we observe papules (red elevations) or pustules (purulent pimples). In the case of deep inflammation, very painful nodules appear and can evolve into abscesses or cysts.

There exist other types of acne that are rarer and more severe:

• Conglobate Acne:

Theacne conglobata or nodulo-cystic acne is characterized by very large comedones. These comedones become inflamed very quickly (deep inflammation), leading to the formation of cysts and nodules. This type of acne is chronic and can leave extensive scars.

• Fulminans Acne (fulminant):

This refers to the rarest and most severe form of acne, primarily affecting men. Unlike other types of acne, this is an acute form of the disease. It is characterized by a significant and striking presence of skin lesions. The uniqueness of this type of acne is the presence of extra-cutaneous signs such as fever (>102.2°F) or joint pain.

• ZOUBOULIS C. C. Acne and sebaceous gland function. Clinics in Dermatology (2004)

• DRÉNO B., What's New in the Pathophysiology of Acne, an Overview (2017)