Generality
The trichogram is the microscopic examination of the hair. This semi-invasive procedure allows you to follow the life cycle of the hair, assessing the state of health and helping the dermatologist to identify the underlying causes of any alopecia.
How it is done
Before the exam
The trichogram, in itself, is a rather simple procedure, which nevertheless requires compliance with some procedural standards to increase the reliability of the results. For example, to avoid misinterpretation, the patient is asked not to wash their hair for at least one week before the test In view of the trichogram, for at least two weeks, friction and cosmetic treatments such as undulations or permanent dyes should also be avoided.
The exam
The trichogram begins with the removal, by pulling, of 50-100 hairs; also in this case the procedure must respect very specific rules. The tear, for example, must be rather decisive and carried out in the direction of hair growth; otherwise it can cause structural deformations of the roots, invalidating the test results.
In the case of diffuse alopecia, the tear must be performed in the site of greatest thinning, while in the case of alopecia areata it must be performed on the edge of the patch and in the contralateral area. In both cases, however, it is good practice to proceed with a further tear from a control area, generally at the occipital level. In fact, for example, in the case of male androgenetic alopecia, the increase in the percentage of hair in telogen affects only the fronto-occipital areas, while in the case of effluvium in telogen the phenomenon is widespread throughout the scalp.
In the event that the patient suffers from seborrhea and / or hyperhidrosis, the sample must also be taken in the temporal areas.
If, on the other hand, the patient suffers from dandruff, the hair removal can only be carried out in the nape area.
The hair sample is then placed on a slide sprinkled with Peruvian balsam, with the hairs arranged parallel to each other. It is covered with a coverslip and proceeded with the examination under an optical microscope or polarized light. Thanks to the optical enlargements, the dermatologist can evaluate in which growth phase the uncorked hair is, observing its structure with particular attention at the root level.
Deepening
Briefly, let us remember that the life cycle of a hair consists of three contiguous phases:
Anagen: is the growth phase, which simultaneously affects percentages varying between 80% and 90% of the hair; its duration, of several months or even years, tends to decrease in the presence of androgenetic alopecia.
Catagen: is the phase of hair loss and lasts about two weeks.
Telogen: is the resting phase of the hair that precedes the fall (catagen), and lasts about 100 days. The length of this period tends to increase in the presence of androgenetic alopecia, up to the inversion of the temporal relationship between anagen and catagen.
Once the roots of the preparation have been examined, the trichogram provides for the detailed count of the number of hairs present in the various phases, followed by the calculation of the relative percentages.
According to the classic dictates, in the normal trichogram the hair percentages in the various phases correspond approximately to the following values:
- Anagen: 80-90% of the hair.
- Catagen: 1-2% of the hair.
- Telogen: 10-20% of the hair.
Diagnosis
Whatever the reference percentages are (variable depending on the equipment used, the operator's experience, the time elapsed between sampling and microscopic examination, etc.), a variation with respect to the standard values is noted in the pathological trichograms. to the clinical picture and to the anamnesis, it represents a precious help in formulating a correct diagnosis.
In alopecia areata, for example, the roots have an easily recognizable dystrophic appearance in the anagen phase, while in androgenetic alopecia the roots in the telogen phase are clearly superior to the norm.
Why do you do it
The trichogram is a very reliable examination that allows to obtain precise information on the health of the hair, allowing to identify any anomalies and alterations in the normal life cycle of the same. Thanks to the information obtained from this examination, it is therefore possible to identify the causes of a "possible hair loss, discriminating whether it is effluvium or outflow and whether this thinning is occurring in the anagen or telogen phase.
Below, the main characteristics of these different forms of hair loss will be described (for more information: Effluvium and Defluvium).
Once the type of thinning afflicting the patient has been established with the help of the trichogram, the doctor may prescribe further tests and analyzes in order to assess the cause of the hair loss. Only in this way will it be possible to undertake the treatment - pharmacological and not - which best suits each patient.
Effluvium in anagen
This condition typically occurs a few days after a particularly stressful event, such as poisoning, a protein-free diet, chemotherapy, exposure to ionizing radiation or febrile illness.
In predisposed subjects, these stressful events cause alopecia areata, which is characterized precisely by a heavy anagen effluvium. In any case, the fall is self-limiting and in general the lost hair grows back spontaneously if the stressful event does not recur.
Telogen effluvium
It is possible to distinguish two different forms of telogen effluvium, acute and chronic.
Acute telogen effluvium
It is also caused in this case by stressful and short-lasting events, which nevertheless occurred not a few days, but about three months before the effluvium. The massive hair loss can be the consequence of surgery, bleeding, bereavement or febrile illnesses. The phenomenon is self-limiting and tends to self-resolve, but in some cases, the dermatologist may still decide to prescribe a drug therapy based on corticosteroids.
Chronic telogen effluvium
In the chronic form of telogen effluvium there is significant and relatively constant hair loss over time. More frequent in women, it is generally linked to a chronic hair growth disorder, often with no tendency to spontaneous resolution. Among the main causes of chronic telogen we mention frequent blood donations, serious mental illnesses, dystyroidism, chronic systemic diseases or prolonged use of some drugs (retinoids, interferon, heparin, some oral contraceptives, allopurinol ...).
The treatment of this form of effluvium involves the administration of corticosteroids topically or orally, depending on the severity of the clinical picture.
Defluvium in anagen
It is characterized by a hair loss higher than the norm, but without the dramatic characteristics of the effluvium. The thinning is due to the progressive loss of the follicles, secondary to their destruction. It is typical of cicatricial alopecias and can represent the consequence of diseases such as lichen planus , discoid cutaneous lupus erythematosus, alopecizing folliculitis, linear scleroderma (morphea), Broq's pseudoarea, trichomalacia and radiation scarring alopecia.
Defluvium in telogen
In most cases, hair loss is characterized by a telogen outflow. This is in fact the characteristic manifestation of androgenetic alopecia, a condition linked to the activity of androgens in a genetically predisposed terrain. As anticipated, this disease is characterized by moderate hair loss, accompanied by their gradual involution (they become increasingly thin, short and depigmented). Unlike the outflow in anagen, in androgenetic alopecia the follicle is preserved, but becomes more and more superficial.
In addition to androgenetic alopecia, both male and female, in women the defluvium in telogen is also accompanied by states of hyperprolactinemia, anorexia nervosa and all forms of alopecia related to hyperandrogenism (syndrome of the polycytic ovary, androgen-secreting neoplasms ...) and / or hypoestrogenism (menopause, postpartum, suspension of the contraceptive pill ...).
For information about the treatment of the aforementioned forms of alopecia, we recommend reading the dedicated articles already present on this site.
