Alopecia

Article Author:
Ahmad Al Aboud
Article Editor:
Patrick Zito
Updated:
3/5/2019 4:35:20 PM
PubMed Link:
Alopecia

Introduction

The term alopecia means hair loss regardless of the cause. It is not exclusive to the scalp; it can be anywhere in the body. Everyone is born with hundreds of thousands of hair on the head. The hair cycle consists of three phases: the growth phase which is called anagen, the resting phase which is called catagen, and the shedding phase which is the telogen.[1] Ninety percent of our hairs are in the growth phase (anagen) and the rest, which corresponds to ten percent in the resting and shedding phases.[2] When the hair is falling out, this is the telogen phase, and the hair is going to recycle, and it starts growing again in the (growth) anagen phase.[3] Alopecia can subdivide into two main categories: scarring and non-scarring.

The most common type is non-scarring or androgenetic alopecia. The majority of men start to lose hairs in the twenties, while women begin to lose their hair in forties or fifties. As an individual grows older, he/she will lose hair. The difference between male hair loss and female hair loss is the pattern. Men generally lose hair in the front and the temporal region, while women tend to lose hair from the central area of the scalp. Also, female hair loss will not end up with complete baldness; whereas male hair loss can end up with complete baldness. Males tend to retain hair at the posterior area of the scalp because this hair is resistant to the androgenic hormone.[4] 

Etiology

Non-scarring alopecia falls into six major categories: 

1) Alopecia areata: this is a patch of hair loss that can affect every part of the body including the scalp, face, trunk, and extremities. When it affects only a portion of the body, it is called alopecia areata. When it affects an entire site, it is called alopecia totalis. When it involves the whole body, it is called alopecia universalis. The etiology is unknown, but it might be related to an autoimmune disease.[5] 

2) Androgenetic alopecia: is a pattern of hair loss that is affected by the genes and hormones (androgenic).

3) Telogen effluvium: results from shifting of the hair cycle growth (anagen) phase towards the shedding (telogen) phase. It may result from an illness like hypo or hyperthyroidism. Also, it can arise from stress like major surgery. Additionally, a crash diet, poor feeding, and drugs can cause telogen effluvium.[6]

4) Traumatic alopecia: like traction alopecia which results from forceful traction of the hair commonly seen in children. Also, trichotillomania is a type of traumatic alopecia in which the patient is pulling his/her hair repeatedly.[7]

5) Tinea capitis: the classical kind of tinea capitis (black-dots) causes non-scarring hair loss unlike other types like kerion and favus.

6) Anagen effluvium: Seen in cancer patients who are receiving chemotherapeutic agents.

Scarring alopecia into three major types:

1) Tinea capitis: the inflammatory variety of tinea capitis (favua) may culminate with scarring alopecia

2) Alopecia mucinosa: infiltration of a localized spot of hair with malignant lymphocytes as in Mycosis fungoides.

3) Alopecia neoplastica: metastatic infiltrate of the scalp hair with malignant cells. 

Epidemiology

Epidemiology is different depending on the cause of alopecia and the type. In alopecia areata, the prevalence is 0.2%, there is no racial or sexual predilection, and it might affect any age group.  Androgenetic alopecia is a common disorder affecting 50% of men and 15% of women, especially postmenopausal women.[8] It affects white races more than dark races. In telogen effluvium, women tend to be more affected than men, but there is no racial or age predilection. In tinea capitis, the incidence is much higher in the pediatric age group and is more common in dark-skin individuals, and there is no sexual predilection.[9] Anagen effluvium is common in cancer patients treated with chemotherapeutic agents.

Pathophysiology

The pathophysiology of alopecia is different depending on the type of alopecia. In alopecia areata, it is unknown, but the most common hypothesis involves autoimmunity in the form of T-cell–mediated pathway. In androgenetic alopecia, both genetic and hormonal androgens play a role in the pathogenesis. In telogen effluvium, the shedding of telogen hairs is under the influence of hormone or stress, but sometimes the trigger is not very clear.[10] In tinea capitis, the dermatophytes infection is responsible for hair loss. In anagen effluvium, the shedding of anagen hairs is under the effect of chemotherapeutic agents. In alopecia mucinosa, the infiltration of the scalp with abnormal lymphocytes is the cause.[11] 

Histopathology

Histopathology is different depending on the cause of alopecia. In patients with alopecia areata, there is peribulbar lymphocytic infiltrate with decreases in the ratio of anagen to telogen hair. In androgenetic alopecia, there are miniaturized hair follicles with an increase in telogen-to-anagen ratio without inflammatory reaction. In telogen effluvium, there is an increase in the numbers of catagen hair. In tinea capitis, there is evidence of fungal infection as under a microscope, and also there is neutrophilic infiltrate. In anagen effluvium, there is a decrease in anagen hairs without any inflammatory response. In alopecia mucinosa, there is an infiltrate of the epidermis, dermis and peribulbar lymphocytic infiltrate mainly anaplastic cells.[12]

History and Physical

In a patient with alopecia, the diagnosis derives from having a good history from the patient. The attending should ask about the number of hairs lost per day and the onset of the issue. In cases of alopecia areata, hair loss can happen overnight while some other types of alopecia may require months or years to become apparent. Also, the physician should ask about the general health of the patient including his/her diet protocol, habits, and overall general condition including recent labs, especially iron, thyroid, ovarian and male hormones. The attending should ask about the usual bathing habits of the patients including shampooing and the use of conditioner. Stress is a significant cause of hair loss, and the physician should inquire about it as well. Family history is contributory in giving a clue for patients who may have a  genetic predisposition towards having androgenetic alopecia.

During the physical examination, it is essential to notice the pattern of hair loss. In a patient with androgenetic alopecia patients tend to lose hair from the frontal and temporal area (male type) and the central scalp area in (female type). In alopecia areata, the patient might lose hair from a single area (alopecia areata classical type), the whole scalp and eyebrows (alopecia totalis), or from the entire body (alopecia universalis). In tinea capitis, the classic presentation is black dots associated with broken hairs while the inflammatory type (favus) correlates with scarring type of alopecia. In telogen effluvium, patients will have diffuse thinning of hairs, and the pull test will be strongly positive. In the pull test, ten hairs are gently pulled from ten different spots, and if 3 or more hairs from these spots are removed, then it would be positive and indicate the underlying cause of hair loss; if less than three hairs are removed, then the test is negative. In a patient with alopecia mucinosa, the patient would have multiple flesh-colored papules and nodules infiltrating the skin of the scalp.

Evaluation

Patients with alopecia need to be investigated thoroughly to look for the type and cause of alopecia. Complete blood count, iron panel, thyroid function test, autoantibodies, total testosterone, and free testosterone, ovarian hormones, luteinizing hormone, and follicular stimulating hormone may be necessary for some patients. KOH preparation and fungal culture in case of tinea capitis are mandatory. Chest x-ray and MRI are required in case of alopecia mucinosa to stage the disease (mycosis fungoides).

Treatment / Management

Depending on the etiology and type of alopecia, the treating physician should direct the treatment plans. In androgenetic alopecia, anti-androgen medications like finasteride along with minoxidil spray will help, but ultimately the patient might require a hair transplant.[13] In alopecia areata, medium potency steroids along with minoxidil spray and topical immunomodulators like tacrolimus may help. In tinea capitis, the mainstay of treatment is anti-fungal medications.

Differential Diagnosis

Non-scarring alopecia:

  • Androgenetic alopecia
  • Alopecia areata
  • telogen effluvium
  • Traction alopecia 
  • Trichotillomania
  • Anagen effluvium

Scarring alopecia:

  • Alopecia mucinosa
  • Metastatic infiltrate
  • Favus

Prognosis

Prognosis depends on the type of alopecia.

Enhancing Healthcare Team Outcomes

Healthcare providers including nurse practitioners should evaluate all cases of alopecia by obtaining a thorough history and conducting a complete physical exam. Patients should be instructed not to wash their hair 24 to 48 hours before the visit to have an accurate pull test. The hair should be examined under a Woods light to check for any elements of fungal infection. If there is any uncertainty about the diagnosis or management, the patient should obtain a referral to a dermatologist.



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      Contributed by Ahmad Al Aboud, MD

References

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