Alopecia is the loss of hair in areas anywhere on the body where hair normally grows. Alopecia may be defined as scarring Scarring Inflammation or non-scarring, localized or diffuse, congenital Congenital Chorioretinitis or acquired, reversible or permanent, or confined to the scalp or universal; however, alopecia is usually classified using the 1st 3 factors. The etiologies of alopecia are usually divided into disorders in which the hair follicle Hair follicle A tube-like invagination of the epidermis from which the hair shaft develops and into which sebaceous glands open. The hair follicle is lined by a cellular inner and outer root sheath of epidermal origin and is invested with a fibrous sheath derived from the dermis. Follicles of very long hairs extend into the subcutaneous layer of tissue under the skin. Cowden Syndrome is abnormal or damaged and those in which the hair follicle Hair follicle A tube-like invagination of the epidermis from which the hair shaft develops and into which sebaceous glands open. The hair follicle is lined by a cellular inner and outer root sheath of epidermal origin and is invested with a fibrous sheath derived from the dermis. Follicles of very long hairs extend into the subcutaneous layer of tissue under the skin. Cowden Syndrome is normal but the cycling of hair growth is abnormal. The most common presentations are androgenetic hair loss, alopecia areata, traction alopecia, tinea capitis Tinea capitis Ringworm of the scalp and associated hair mainly caused by species of Microsporum; Trichophyton; and Epidermophyton, which may occasionally involve the eyebrows and eyelashes. Dermatophytes/Tinea Infections, and telogen effluvium Telogen Effluvium Dermatologic Examination. Diagnosis is made through a positive medical history and physical exam findings. Treatment depends on the type and potential for regrowth.
Last updated: 1 Feb, 2021
The 3 stages of hair growth:
Anagen represents the periods of active growth; 90% of all hair follicles are in the
anagen phase
Anagen phase
Skin: Structure and Functions. Catagen represents the periods of degeneration and
regression
Regression
Corneal Abrasions, Erosion, and Ulcers of the
hair follicle
Hair follicle
A tube-like invagination of the epidermis from which the hair shaft develops and into which sebaceous glands open. The hair follicle is lined by a cellular inner and outer root sheath of epidermal origin and is invested with a fibrous sheath derived from the dermis. Follicles of very long hairs extend into the subcutaneous layer of tissue under the skin.
Cowden Syndrome; < 1% of all hair follicles are in the
catagen phase
Catagen phase
Skin: Structure and Functions. Telogen represents the resting periods; < 10% of all hair follicles are in the
telogen phase
Telogen phase
Skin: Structure and Functions. After the
telogen phase
Telogen phase
Skin: Structure and Functions, the hair naturally falls out.
The most common classifications of hair loss are cicatricial ( scarring Scarring Inflammation) alopecia, non-scarring alopecia, and structural hair disorders.
Cicatricial ( scarring Scarring Inflammation):
The hair follicle Hair follicle A tube-like invagination of the epidermis from which the hair shaft develops and into which sebaceous glands open. The hair follicle is lined by a cellular inner and outer root sheath of epidermal origin and is invested with a fibrous sheath derived from the dermis. Follicles of very long hairs extend into the subcutaneous layer of tissue under the skin. Cowden Syndrome undergoes irreversible damage, which heals through fibrosis Fibrosis Any pathological condition where fibrous connective tissue invades any organ, usually as a consequence of inflammation or other injury. Bronchiolitis Obliterans, leading to a cessation in hair cycling and permanent hair loss.
Lymphocytic | Neutrophilic | Mixed |
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Non-scarring:
Inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation is mild or absent so that the hair follicle Hair follicle A tube-like invagination of the epidermis from which the hair shaft develops and into which sebaceous glands open. The hair follicle is lined by a cellular inner and outer root sheath of epidermal origin and is invested with a fibrous sheath derived from the dermis. Follicles of very long hairs extend into the subcutaneous layer of tissue under the skin. Cowden Syndrome is not damaged, resulting in non-permanent hair loss (divided into 3 subtypes: focal, patterned, and diffuse).
Focal | Patterned | Diffuse |
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Structural hair disorders:
Structural hair disorders are inherited or acquired disorders of hair structure that result in brittle or fragile hair, which lead to hair breakage or the appearance of hair growth failure Growth failure Chronic Granulomatous Disease.
Inherited | Acquired |
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Medical history:
Physical exam:
Normal scalp trichoscopy:
Multiple hair fibers can be seen to emerge from a single
infundibulum
Infundibulum
Uterus, Cervix, and Fallopian Tubes: Anatomy.
Trichoscopy:
In
androgenetic alopecia
Androgenetic Alopecia
Dermatologic Examination, a reduction in the number of hairs per follicular unit precedes the development of baldness.
Pull test:
Approximately 60 hairs are grasped from the proximal portion of the scalp and tugged from the proximal to the distal end.
Additional tests:
Androgenetic alopecia Androgenetic Alopecia Dermatologic Examination is a hereditary type of hair loss that is mediated by the presence of the androgen dihydrotestosterone Dihydrotestosterone A potent androgenic metabolite of testosterone. It is produced by the action of the enzyme 3-oxo-5-alpha-steroid 4-dehydrogenase. Gonadal Hormones ( DHT DHT A potent androgenic metabolite of testosterone. It is produced by the action of the enzyme 3-oxo-5-alpha-steroid 4-dehydrogenase. Gonadal Hormones) and is the most common type of alopecia.
Androgenetic alopecia Androgenetic Alopecia Dermatologic Examination, or male-pattern hair loss
Image: “Alopecia” by Welshsk. License: CC BY 3.0Alopecia areata is a chronic, relapsing, autoimmune disorder Autoimmune Disorder Septic Arthritis in which the body’s immune system Immune system The body’s defense mechanism against foreign organisms or substances and deviant native cells. It includes the humoral immune response and the cell-mediated response and consists of a complex of interrelated cellular, molecular, and genetic components. Primary Lymphatic Organs targets anagen hair follicles and causes non-scarring hair loss.
Alopecia areata in a man showing the characteristic smooth, circular, and discrete patch Patch Nonpalpable lesion > 1 cm in diameter Generalized and Localized Rashes of hair loss on the scalp
Image: “Alopecia areata” by Thirunavukkarasye-Raveendran. License: CC BY 4.0A 12-year-old patient with alopecia totalis
Image: “Alopecia totalis” by Department of Dermatology, Jahrom Medical School, Jahrom, Iran. License: CC BY 2.0Traction alopecia is a type of non-scarring hair loss caused by repetitive or prolonged tension on the hair.
Traction alopecia in an African American woman due to traction hairstyles
Image: “Figure 6” by Xu, Liu and Senna Senna Laxatives. License: CC BY 4.0Tinea capitis Tinea capitis Ringworm of the scalp and associated hair mainly caused by species of Microsporum; Trichophyton; and Epidermophyton, which may occasionally involve the eyebrows and eyelashes. Dermatophytes/Tinea Infections is a fungal infection of the scalp typically presenting as pruritus Pruritus An intense itching sensation that produces the urge to rub or scratch the skin to obtain relief. Atopic Dermatitis (Eczema) and scaling, leading to secondary cicatricial ( scarring Scarring Inflammation) alopecia.
Tinea capitis
Tinea capitis
Ringworm of the scalp and associated hair mainly caused by species of Microsporum; Trichophyton; and Epidermophyton, which may occasionally involve the eyebrows and eyelashes.
Dermatophytes/Tinea Infections in a child showing a common variant of a singular scaly
patch
Patch
Nonpalpable lesion > 1 cm in diameter
Generalized and Localized Rashes with hair loss:
This is a common
presentation
Presentation
The position or orientation of the fetus at near term or during obstetric labor, determined by its relation to the spine of the mother and the birth canal. The normal position is a vertical, cephalic presentation with the fetal vertex flexed on the neck.
Normal and Abnormal Labor of ectothrix infection caused by
Microsporum
Microsporum
A mitosporic oxygenales fungal genus causing various diseases of the skin and hair. The species microsporum canis produces tinea capitis and tinea corporis, which usually are acquired from domestic cats and dogs. Teleomorphs includes arthroderma (nannizzia).
Dermatophytes/Tinea Infections species.
Tinea capitis
Tinea capitis
Ringworm of the scalp and associated hair mainly caused by species of Microsporum; Trichophyton; and Epidermophyton, which may occasionally involve the eyebrows and eyelashes.
Dermatophytes/Tinea Infections in children:
The left shows the variant kerion which is described as inflammatory plaques with pustules, thick crusting, and/or drainage that develop due to an intense inflammatory immune response.
Pain
Pain
An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons.
Pain: Types and Pathways and tenderness are present. The right shows the variant of
patches
Patches
Vitiligo of hair loss with black dots that is a common
presentation
Presentation
The position or orientation of the fetus at near term or during obstetric labor, determined by its relation to the spine of the mother and the birth canal. The normal position is a vertical, cephalic presentation with the fetal vertex flexed on the neck.
Normal and Abnormal Labor of endothrix infection caused by
Trichophyton
Trichophyton
A mitosporic fungal genus and an anamorphic form of arthroderma. Various species attack the skin, nails, and hair.
Dermatophytes/Tinea Infections.
Telogen effluvium Telogen Effluvium Dermatologic Examination is defined as the premature Premature Childbirth before 37 weeks of pregnancy (259 days from the first day of the mother’s last menstrual period, or 245 days after fertilization). Necrotizing Enterocolitis transition of hair follicles into the resting state (telogen) after a physiologic or psychologic stressor, which leads to diffuse, non-scarring alopecia.
Chronic
telogen effluvium
Telogen Effluvium
Dermatologic Examination:
Note typical temporal recession. The hair density is otherwise normal.
The following are other conditions that can cause alopecia: