What are the different types of acne?

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

Acne presents itself through the emergence of inflammatory or non-inflammatory spots. 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 synthesised 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 spots.

• An abnormal follicular keratinisation:

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

• A bacterial colonisation:

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 hyperkeratinisation of the pilosebaceous follicles.

Please note : acne has multifactorial origins, there are several factors that can promote its appearance such as diet, 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 keratinisation, 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 occurs). 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 spots). In the case of deep inflammation, very painful nodules appear and can progress to abscesses or cysts.

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

• Conglobate Acne:

Theacne conglobata or nodulocystic acne is characterised 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 scarring.

• Fulminans Acne (fulminant):

This refers to the rarest and most severe form of acne, which primarily affects men. Unlike other types of acne, this is an acute form of the disease. It is characterised by a significant and striking presence of skin lesions. The specificity of this type of acne is the presence of extra-cutaneous signs such as fever (>39°C) 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)