What is alopecia and what types of alopecia are there?

Hair loss disorders or alopecia are a large and heterogeneous group of conditions that present various clinical characteristics and causes.Hair loss can be due to disorders of the hair cycle, inflammatory conditions that damage the hair follicles, or inherited or acquired factors in the hair shaft.

What types of alopecia are there?

One way to classify the different forms of hair loss is the distinction between non-scarring alopecia and scarring alopecia.

• In thenon-scarring alopecia, the hair follicle is not permanently damaged, so spontaneous growth or growth in response to treatment is possible in most cases.
• Thescarring alopeciaare inflammatory changes in the scalp that lead topermanent losshair related.

Non-scarring alopecia

In non-scarring alopecia, the destruction of the hair follicle does not occur.One way to classify this type of alopecia is by distributing hair loss.

Focal hair loss

• Alopecia areata:is a relatively common form of non-scarring alopecia in which an autoimmune process contributes to hair loss on the scalp or other areas.The defense cells of our own immune system attack the root of the hair producing an inflammation that causes its fall.Therefore, the hair will not grow back until this inflammation has stopped.Most often, hair loss occurs in isolated oval patches.Sometimes alopecia areata can progress to the loss of all hair on the scalp or body, known as universal alopecia areata.

• Traction alopecia:It is the result of prolonged stress on the hair follicle, usually due to hairstyles such as pigtails or tight braids.Normally, it is detected on the most frontal and lateral part of the scalp.Prolonged traction can lead to a transition to scarring alopecia with permanent hair loss.

Hair loss following a characteristic pattern

• Male androgenetic alopecia:Androgenetic alopecia is caused by the action of androgens in the hair follicles of the areas most sensitive to androgens (crown, top and forehead) in genetically susceptible men.The hairs of the scalp exist in the form of clusters composed of three to five follicles that produce hair shafts.In male androgenetic alopecia, one by one, the follicles thin out (which is called miniaturization), and little by little only one or two terminal hairs begin to be produced.Once all the follicles are miniaturized, baldness is observed.

• Female pattern hair loss:It most often presents as a thinning of the hair in the frontal and crown areas of the scalp, with a relative preservation of the posterior scalp.The frequency of this condition increases with age.

Diffuse hair loss

• Anagen effluvium:It occurs as a result of an acute interruption of the growth phase (anagen) and results in severe hair loss.Hair loss usually occurs within two weeks of a triggering event.For example, chemotherapy treatment is one of the main causes of anagen effluvium.
• Telogen effluvium:Various alterations are capable of modifying the biological clock of the hair follicles, and it is possible that an abnormally high number of hair enters a phase of loss simultaneously.When this occurs, the hair loss is called telogen effluvium.Some examples of factors that can stimulate acute telogen effluvium are diseases such as COVID, major psychological stressors, childbirth, dietary restriction, andsome medications.Hair loss usually occurs two to three months after the event that caused it.
• Other:Non-scarring alopecia can also occur as a direct consequence of the involvement of the scalp by inflammatory skin diseases.For example, psoriasis, atopic dermatitis, and seborrheic dermatitis can cause focal or diffuse hair loss.

Scarring alopecia

Fibrosing frontal alopecia

There are several types of scarring alopecia, however we will focus on thefibrosing frontal alopeciasince it is an increasingly frequent form of scarring alopecia and the cause of which continues to be the subject of investigation.

Patients have aband alopeciathat most frequently affects the frontal area (area of the headband) of the scalp.

Theeyebrow involvementit is frequent and can precede hair loss.

There are multiple causes that can cause alopecia as well as multiple forms of presentation.

The most important thing when suspecting alopecia is to consult your dermatologist to make a correct diagnosis and be able to guide the appropriate treatment for each condition.