Quite a rare disease, which, nevertheless, attracts the attention of many scientists. It is interesting that the loss of hair, starting with complete well-being, just as suddenly stops. It can last a long time and lead to complete baldness in some parts of the head or even the body, and can quickly stop. The most interesting is that a person who has been completely bald for years, can grow normal hair literally in a month. And then lose them again. Hair with focal alopecia seems to live their own lives, leaving their heads and going back when they want.
Alopecia areata usually begins with a small patch of alopecia growing into a total loss of hair on the head (A. totalis) or on the whole body (A. universalis). Hair loss can occasionally be diffuse (A. diffusd), for example, limited to the beard area of men (A. barbae), or can develop not only on the head, but also on other hairy areas of the body. Extensive hair loss is observed only in a small part of people affected by focal alopecia, which is about 7%, although in the recent past this part of the patients was 30%.
There are three types of hair fibers along the edge of the patch of alopecia – tapered, club-shaped and exclamation mark. Restoring hair is thin and unpigmented, and only later they get a normal color and texture. Hair restoration can occur on one part of the head, while in another area, hair loss can continue.
From 7 to 66% of people suffering from focal alopecia have deviations in the formation of nails (on average 25%). Dystrophy of the nails can fluctuate from weakly expressed (roughness, shabbiness) to an extreme degree.
Alopecia areata can occur with varying degrees of damage – from small inhomogeneous areas to extensive hair loss throughout the body or diffuse thinning of the hair. The causes of such different manifestations of the disease have not been studied well enough.
For a long time it remained to be questioned whether different forms of hair loss were the same disease. In the emergence and development of the disease, there appear to be some differences that are not yet known to scientists. Intensive research is being carried out in this direction, and something has already been clarified.
For example, it is known that hair follicles in different parts of our body can vary greatly in size and shape. The same hormones can have different effects on bulbs located on different parts of the body. It is established that androgenic hormones cause increased hair growth, especially in the region of the beard. These same hormones, apparently, have the opposite effect on scalp hair follicles, which gradually leads to forms of baldness, characteristic of men, in which baldness affects mainly the scalp area.
At present, the theory of the L-mosaic of the skin, which partly explains the differences in hair follicles in different parts of the body, has gained the greatest support of scientists. The cells that make up our skin come from a very small number of embryonic cells, and the skin can be divided into different parts depending on which embryonic cells they originated from. So, it is known that the skin and scalp of the occipital part of the head differ from the macular area. Particularly interesting is the fact that in the form of focal alopecia described as Alopecia lophiasis, hair loss occurs only on the occipital part of the head, while adjacent areas are not affected.
Of course, it is tempting to relate the nature of hair loss to its origin, but there is no direct evidence to support this assumption. It is assumed that the pigmented hair is more prone to focal alopecia as compared to blond hair. When developing the disease in brown-haired people or people with light-brown hair, as a rule, the first ones are affected by bulbs of pigmented hair, and only later the hair falls out. Due to this fact, some dermatologists believe that the effect of the immune system is specifically directed at cells producing melanin. With a rare form of focal alopecia (Alopecia areata naevi), hair loss occurs in the immediate vicinity of pigmented spots or moles. It is assumed that the areas around the hyperpigmented skin areas are more sensitive to the disease.
Who is most often prone to focal infection
Demographic studies have shown that 0.05-0.1% of the population undergoes alopecia, at least once. In England, patients with alopecia make up 30-60 thousand, in America – 112-224 thousand and in the whole world – 2.25-4.5 million people. The first signs of alopecia appear in most people aged 15-25 years. It is shown that in 10-25% of cases the disease has a family origin. Most people suffering from focal alopecia are healthy, except for cases of alopecia caused by Down’s syndrome, Addison’s disease, thyroid disorders, vitiligo, etc.
There are two points of view about the incidence of focal alopecia in men and women. Or it is believed that the disease affects men and women equally (1: 1), or more women (2: 1). In most other autoimmune diseases, an even greater number of women are exposed to the disease (10: 1 with systemic lupus erythematosus). It is believed that this is due to differences in the hormonal levels of men and women. Humoral and cellular immunity of women is on average more active than in men, it is better to fight with bacterial and viral infections. But such a highly mobile immunity is more susceptible to the development of autoimmune activity. It is known that many hormones, including sex steroids, adrenaline, glucocorticoids, thymus and prolactin hormones, affect the activity of lymphocytes. But the most powerful hormone that affects the immune system is estrogen – a female sex hormone.
Modern ideas about the pathogenesis of focal infection
Speaking about the pathogenesis of any disease, it is necessary to highlight two main points: the cause of the disease and the mechanism of development.
Factors leading to focal alopecia
The most common assumptions about what is the trigger signal for the development of focal alopecia are the following:
Mental stress. Stress is often seen as the cause of focal alopecia, but this hypothesis is confirmed only statistically. There was no direct relationship between stress and alopecia. It is extremely difficult to conduct such studies, since stress often occurs due to hair loss. Rather, stress can be regarded as an external factor that triggers focal alopecia in people predisposed to it.
Physical trauma. In the literature, many cases of how a physical trauma triggers the development of focal alopecia are described. Any event that stimulates the immune system, be it a blow to the head or an infection, can be a potential cause of the disease. Recently, a real link between the trauma and autoimmune diseases was demonstrated. Under the influence of physical stress, cells can produce heat shock proteins (HSP). HSPs play an important role in the development of the immune response and are involved in many autoimmune diseases: rheumatoid arthritis, systemic lupus erythematosus and some others.
Infection. In the literature, there are descriptions of cases of hair loss after the transferred infectious diseases, including skin infections. Currently, scientists explain this phenomenon through the development of an immune response in response to the introduction of a foreign antigen.
Genetic predisposition. It was shown that focal alopecia often occurs in relatives. It is believed that, at least, some people have a genetic predisposition to focal alopecia.
The role of autoimmunity in the development of focal alopecia
The causes of focal alopecia are still unknown. The point of view of focal alopecia as an autoimmune disease is very popular among scientists. As the main evidence, observations are made of the infiltration of immune cells around and in the hair follicles, as well as a number of known facts of restoring hair growth in some patients with focal alopecia after immunosuppressive therapy.
The remaining evidence follows when comparing alopecia areata with other autoimmune diseases.
Admittedly, such indirect evidence in support of the autoimmune origin of this disease is not 100%. Theoretically, there are many possible pathogenic pathways that can lead to the appearance of an infiltrate of immune cells. All these paths can be divided into three main groups.
- The cause of the infiltration, leading to hair loss, is an infection.
- Alopecia causes autoimmunity. At the same time, the immune system functions abnormally against normal functioning hair follicles.
- Alopecia is also caused by autoimmunity, but in this case the tissues of the hair follicles are damaged, which leads to the production of follicles of their own antigens, to which the immune system responds. In other words, the immune system functions normally against abnormally functioning hair follicles.
According to the classical scheme of autoimmunity, the development of focal alopecia would begin with the appearance of autoreactive antigens in the hair follicles, which would be attacked by the immune system. But so far, suspicious antigens, which should have been present in the hair follicles of patients, have not been found.
In other variants of autoimmune diseases, autoantibodies play an active role. Autoantibodies recognize their own antigens and begin destructive activity against them. Usually such destructive activity is directed to certain tissues and organs, although there are antibodies that do not show obvious effects.
Most people have a low level of autoantibodies in the blood, and they do not have any damaging effect. However, even a high level of autoantibodies with some autoimmune diseases does not have obvious activity. Characterization of antibodies contained in the blood of patients is often used to diagnose certain diseases. There have been many studies of autoantibodies in focal alopecia, but the results are contradictory. Some scientists believe that the level of autoantibodies in various organs increases with focal alopecia.
Others believe that there is no significant change in the level of autoantibodies. By indirect immunofluorescence in the serum of patients with focal alopecia, antinuclear antibodies were detected (certain types of antinuclear antibodies are associated with autoimmune diseases such as systemic lupus erythematosus and rheumatoid arthritis).
Attempts to identify autoantibodies against components of hair follicles in the serum of patients with focal alopecia were unsuccessful. However, not so long ago it was found that in the serum of healthy people there may be a low level of specific autoantibodies against hair follicles. The significance of these autoantibodies is still not understood. Autoantibody of B cells is one of the variants of autoimmune disease, in other cases immune cells have simply an impaired type. CD4 + and CD8 + lymphocytes – the main cells that appear around injured hair bulbs – are alternative candidates for explaining the causes of focal alopecia. To fully understand the role of the immune system in this disease, it must be considered in all its complexity and consider various options.
Alternative explanations for the development of focal alopecia
A small part of dermatologists are disputing the autoimmune origin of focal alopecia. With the use of PCR (polymerase chain reaction) in the skin of patients with focal alopecia, genes encoding cytomegalovirus (CMV) were found, while in healthy people they were not found. Studies in this area have been conducted relatively recently, but scientists suggest that the presence of CMV in hair follicles causes an immune response, which can also lead to abnormalities and damage to the surrounding tissue. However, this hypothesis requires solid evidence, at least it is necessary to show that CMV is indeed capable of causing alopecia.
It is still not clear what exactly is the target for the cells of the immune system in this disease, but the possibility of the origin of the target from an external source is still not disproved. These studies do not negate the immune mechanism of development of focal alopecia. And yet, since the activation of immune cells in response to a viral antigen occurs, this mechanism of development of focal alopecia can not be defined as truly autoimmune in nature. However, the initial reaction to viral antigens in the future may lead to an autoimmune effect.
Another assumption about the cause of focal alopecia was the “starvation” of hair follicles, caused by a weak circulation of blood due to narrowing of the surface vessels. However, it was not confirmed experimentally.
At present, it is believed that susceptibility to focal alopecia is polygenic. This means that there are a number of genes that, if they exist, make a person more susceptible to the disease. The trigger mechanisms appear to be external factors, but the extent of the lesion, the nature of the course and the resistance to treatment are determined by the presence and interaction of several genes.
It is not necessary that all these genes are present simultaneously, but the more of them, the worse the prognosis. The HLA genes located on chromosome 6 encode the proteins of the main histocompatibility complex (MHC). These proteins are expressed on the cell surface and serve to recognize the antigen and own cells with the help of immune cells. To date, it has been found that some HLA alleles are more characteristic of patients with focal alopecia. Recently, it has been shown that alleles of these types are present in 79% of patients. Expression of such genes encoding MHC proteins inside the affected hair follicle is often obvious, but its true value remains questionable. Probably, there are many more alleles associated with focal alopecia, which encode other factors. The search for such factors, which could serve as genetic markers for focal alopecia, does not stop.
Diagnosis of focal alopecia
Until now, there is no reliable diagnosis of focal alopecia. Dermatologists diagnose the method of successively eliminating the causes of hair loss, and with close examination of the damage itself. Usually at the initial stage the disease manifests itself in the form of a small spot, the development of which can last for 24 hours. Some people feel tingling or even pain on the affected area.
Focal alopecia can occur on any part of the body, but the scalp is most often affected. In the early stages of the disease, the hair protruding in the form of an exclamation mark is seen along the edge of the affected area. The primary test is the hair strength test. If the hair is easily pulled out, then the disease is in the active phase, and further hair loss will occur. For more accurate diagnosis, dermatologists usually take a skin biopsy (a small piece of skin – 4 mm in diameter) for microscopic analysis.
The strategy of treatment of alopecia
Hair is capable of recovery even after many years of disease. In many patients, especially those with a mild illness, spontaneous hair restoration is possible. However, with proper treatment, remission occurs even in cases of severe illness. Of course, there are incurable cases, and cases where hair growth is restored only with constant treatment, and when it stops hair again falls out in a few days. In some patients, despite the treatment, the disease recovers. Unfortunately, there are no universal means and methods for treating focal alopecia. Here are some useful practical tips:
- to maximally improve the cosmetic effect of treatment of intense, conspicuous focal alopecia, it is necessary to treat the surface of the entire head, and not only obviously affected areas;
- do not expect any positive changes earlier than three months after the start of any treatment taken;
- cosmetic restoration of hair growth can occur within a year or more, constant treatment increases the probability of permanent hair growth, but individual patches of baldness can then appear, then disappear again;
- in patients with intermittent hair loss, the effect of treatment improves with prophylactic administration of antihistamines;
- the growth of hair is also facilitated by the preventive intake of multivitamins; in severe cases, injections of B vitamins are recommended;
- an important factor for the effectiveness of treatment is the psychological factor.
There are a number of treatments that can achieve some success, but when they are reversed, the disease returns. All currently used methods of treatment are most effective in mild forms of the disease and less effective in severe lesions. Different methods of treatment can be divided into several groups:
- nonspecific stimuli: anthralin, croton oil, dithranol, etc .;
- agents that cause contact dermatitis: dinitrochlorobenzine, diphenylcyclopropenone, dibutyl ester of squaric acid, etc .;
- nonspecific immunosuppressors: corticosteroids, 8-label-sepsoralen in combination with UV-A (PUVA-therapy);
- specific immunosuppressors: cyclosporin (SuA);
- methods of direct action on hair bulbs: Minoxidil;
- non-traditional methods of treatment;
- experimental treatment: neoral, tacrolimus (FK506), cytokines.