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CAUSES OF HAIR LOSS

ALOPECIA AREATA

TELOGEN EFFLUVIUM

ANAGEN EFFLUVIUM

LOOSE ANAGEN SYNDROME

HEREDITARY/CONGENIAL HAIR ABNORMALITIES

TRIANGULAR ALOPECIA

HAIR LOSS AS A SYMPTOM OF UNDERLYING DISEASE

CANCER OF THE SCALP

TRICHOTILLOMANIA

SCARRING ALOPECIA

CENTRAL CENTRIFUGAL SCARRING ALOPECIA

FOLLICULAR DEGENERATION
SYNDROME

FOLLICULAR DECALVANS

PSEUDOPELADE

FOLLICULITIS KELOIDALIS NUCHAE

Androgenetic alopecia is the most common cause of hair loss in men, and occurs in women as well. In men it is called male-pattern hair loss. Androgenetic alopecia patterns of hair loss are significantly different in women than in men and the underlying cause(s) may be more complex than in men.

A genetic predisposition for androgenetic alopecia has long been recognised. The condition quite obviously "runs in the family". The genetic predisposition to lose hair can be inherited from the mother, father, or a combination of both. Researchers are still trying to work out exactly why two people with the same genetic makeup can have different patterns of hair loss.

While the underlying cause of androgenetic alopecia is genetic, the direct cause is due to the effect dihydrotestosterone (DHT) has on the hair follice receptors. The parent molecule of DHT is testosterone - an androgenic or "male" hormone that is essential to the development of male characteristics (testosterone is also present in females, but at much lower levels than in males). Testosterone is converted to the physiologically more active DHT by the action of an enzyme, 5-alpha-reductase type 2.

In order to be effective, DHT must pass unhindered into its target cells. This is accomplished when DHT "docks" with an androgen receptor (AR) on the cell surface. The AR is a specially configured protein that has the single function of docking with the DHT molecule. When the docking is effective, the DHT-AR complex binds to DNA in the cell and regulates the activity of DHT-responsive genes. The DHT-AR complex has specific affinity for the DNA in target cells, initiating the down-regulation of gene expression necessary for hair growth.

Androgenetic alopecia is caused by altered access of DHT to androgen receptive target cells in the hair follicle. The result is to shorten the growth cycle so hair is shed earlier than usual, and to impede the growth of new hair with the effect that a follicle produces only vellus-like ("peach fuzz") hair. As this process progresses, the hair will eventually not regenerate and baldness will ensue. This process is known as miniaturisation.

Standard Classification of Male-Pattern Hair Loss Due to Androgenetic Alopecia

Standard Classification of Female-Pattern Hair Loss Due to Androgenetic Alopecia

The peak period of onset for female-pattern hair loss tends to occur later in life than in males; onset in the 40-50 age range is not uncommon. As in males, early onset tends to be associated with more severe eventual hair loss. In both males and females, hair follicles at the back of the scalp are not affected by the genetically-driven processes of androgenetic alopecia. The protected follicles at the back of the scalp provide the reservoir for use in hair transplantation or other surgical means of hair restoration.

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Alopecia areata is a hair-loss condition that affects millions of people worldwide. A defining feature of alopecia areata is patchy hair loss on the scalp that can progress to loss of hair over the entire scalp or even the entire body. Hair loss may or may not be permanent.

Apparent associations have been noted between the presence of alopecia areata, and the presence of other conditions including psoriasis and Type 1 diabetes. The simultaneous occurrence of alopecia areata with these conditions prompted investigators to look for "candidate genes". Investigations have indicated that genes on at least four chromosomes may be involved in alopecia areata, as well as (1) factors such as interaction between hair follicle genes and the body's immune system, and (2) environmental influences unspecified to date.

Telogen effluvium is an abnormality of hair cycling in which hairs in anagen (growth) phase are rapidly shifted to telogen (resting) phase, and subsequently shed. Hair loss due to telogen effluvium is typically discovered when extraordinary hair shedding is noted in comb, brush, hat or on a pillow.

A great variety of causes are known for telogen effluvium. If the cause can be identified and removed, telogen effluvium may resolve over a period of weeks to months. If a cause cannot be discovered and removed, the abnormal hair cycling and hair shedding can become chronic.

Known causes of telogen effluvium include:

• Hormonal - hypothyroidism, post-pregnancy hormonal changes, pre- or post-menopausal hormonal changes.
• Physical illness - anaemia, systemic disease involving major organs, major surgery.
• Nutritional - deficiency of some or all of calories, protein, essential fatty acids, vitamins, minerals (deficiency may sometimes be caused by nutrient-deficient diets, sometimes by inability to absorb or metabolise nutrients).
• Drugs - many prescribed and over-the-counter drugs have been implicated; sometimes it is difficult to distinguish the effect of a drug from the effect of a condition for which it is taken.
• Severe acute or chronic psychological stress - may be involved in physical illness in a primary or secondary role.

A condition is which hair in the anagen (growth) phase of the hair cycle is shed, often by breaking off at the level of the scalp. A frequent cause is exposure to a toxic agent (such as chemotherapy drugs, colchicine, mercury, thallium), ionising radiation (cancer therapy or accidental exposure), and severe protein restriction in a protein-deficient diet.

Some toxic agents, notably thallium, can be fatal after a single dose because they cannot be removed from tissue before they cause death. Anagen effluvium usually resolves after removal of the toxic agent or addition of sufficient protein to the diet. The classic condition due to protein-calorie malnutrition is kwashiorkor, recognized especially in children with protruding abdomens and tangled, broken hair.

The name "loose anagen syndrome" has been given to a condition in which hair in the anagen (growth) phase is easily pulled from hair follicles by combing, brushing or simply by running the fingers through the hair. The incidence of loose anagen syndrome appears to be highest in fair-haired people, especially in fair-haired children. The condition is genetic in origin. Symptoms may slowly improve with advancing age. In some patients, loose anagen syndrome is accompanied by features of other familial conditions that cause hair to be woolly and uncombable.

Hair loss and hair shaft abnormalities of hereditary or congenital cause usually become apparent in infancy or early childhood. Conditions range from total hair loss in infancy to hair shaft abnormalities such as hair breakage, misshapen hair shafts such as "bamboo hair" and "twisted" hair, woolly hair and uncombable hair. Congenital hair abnormalities may be associated with underlying congenital disorders that require the attention of a paediatric specialist.

As implied by its name, triangular alopecia is the loss of hair in a triangle-shaped patch, usually above the temple. The condition may be congenital and often appears in childhood. Hair loss is usually permanent.

Hair loss can be a symptom, even an initial symptom, of underlying disease involving the endocrine system (pituitary, thyroid, adrenal glands), digestive system (intestines, liver), urinary tract (kidneys) or skin. Unexplained hair loss should be pursued by medical examination.

Persistent scalp lesions with or without hair loss can be an indication of a primary skin cancer or a metastasis from another site. A persistent scalp lesion should be examined by a physician.

This "hair plucking mania" is a condition in which hair loss is caused by the individual's obsessive/compulsive plucking of his/her own hair. In a mild form, the plucking may be a routine, semi-automatic behaviour while the individual reads, watches, television, etc. In more severe obsessive/compulsive form, the plucking is consciously carried out, perhaps in front of a mirror.

The individual is likely to deny the behaviour, even when evidence of plucked patches is clear. The consciously compulsive hair plucker will usually conceal plucking instruments and discard plucked hairs to avoid discovery. In contrast, piles of plucked hairs may be discovered around the semi-automatic plucker's favourite chair.

Trichotillomania is a condition requiring psychological evaluation and treatment.

Injury to the scalp can be caused by physical trauma and disease. Injury can result in destruction of hair follicles and scarring of the scalp, with permanent hair loss.

Physical, Chemical, Thermal and Radiation Injury

Physical Injury: Laceration

• Automobile accident
• Workplace accident
• Criminal assault

Physical Injury: Traction

Corn-rowing and tight braiding can exert enough pressure on skin and hair follicles to cause injury and scalp scarring, with permanent hair loss.

Chemical Injury

• Hair-straightening chemicals, especially in "home-made" solutions, are capable of causing chemical injury to the scalp and destruction of hair follicles with scalp scarring. Chemicals that can soften the strong fibres of the hair shaft are potent enough to injure scalp skin.
• Hair bleaches can injure scalp skin, especially with recurrent use.
• Permanent waving solutions may cause scalp injury, especially with frequent recurrent use.
Thermal (Heat) Injury
• Accidental injury - house fire, automobile crash with fire, explosion with fire.
• Permanent waving with excessive heat.

Radiation Injury

Exposure to ionising radiation above the level regarded as safe can cause tissue destruction and scarring.

This is a broad classification of scarring alopecias that have some features in common.

A condition that has high incidence in people of African ancestry, its defining feature is degeneration and death of hair follicles on the scalp. While the cause is unknown, suspected causes or contributing factors are excessive use of (1) hot-comb hair straightening, and (2) chemical hair straightening.

Areas of scalp inflammation also exhibit boggy patches with boil-like pustules and scabby crusts. Moist areas may be infected with skin bacteria, but whether the infection is cause or effect is not known. Immune system dysfunction is also suspected as a cause.

Pseudopelade is a condition of unknown cause that slowly progresses from small patches of hair loss to large areas of permanent hair loss and scalp scarring. Lesions are not markedly inflamed. The incidence of the condition is higher in women than in men. Pseudopelade is frequently discovered when a small patch of hair loss is noted while combing, brushing or styling hair. The cause is unknown.

Inflamed hair follicles progress to acne-like lesions and eventual formation of the lumpy scars called keloids. Incidence is higher in people of African ancestry, who also have a genetic predisposition to form keloidal scars after injury. The lesions of folliculitis keloidalis nuchae occur frequently on the back of the neck just below the hairline, but also can involve the scalp. Cause of the condition is unknown.

A number of diseases of known or suspected autoimmune origin can cause scarring alopecia. These include cutaneous sarcoidosis, lupus erythematosis, lichen planus and lichen planopilaris. Cutaneous sarcoidosis is known as the "great imitator" because its appearance can be so similar to that of other conditions. Sarcoidosis is a systemic disease that can affect every organ system, including skin.

Cutaneous sarcoidosis (sarcoidosis of the skin) occurs in about a third of patients with systemic sarcoidosis. Clinical features include scaly scalp skin, tender red nodules just under the skin's surface, lumpy papules and decolourised patches on the skin. On visual inspection alone, it is difficult to differentiate cutaneous sarcoidosis from other skin diseases such as lichen planus and lupus erythematosis. A full diagnostic workup including skin biopsy may be necessary to confirm a diagnosis. The cause of sarcoidosis is unknown, but an autoimmune origin is suspected.

Bacterial, viral and fungal scalp infections that are severe or prolonged may cause scalp injury, scalp scarring and hair loss.

Skin cancer that invades deep layers of the skin can destroy hair follicles and cause scalp scarring.

The most common type of scalp scaling is the condition popularly known as "dandruff". Almost everyone has experienced "dandruff" at some time, usually in the appearance of whitish to yellowish-white flakes on clothing and bedding as well as clinging to hair. "Dandruff" is regarded as unsightly and socially embarrassing. A great many proprietary shampoos, lotions and ointments are marketed as "anti-dandruff" treatments.

Although "dandruff" is the all-encompassing term for scales shed from the scalp, there are a number of different and distinct causes of scalp scaling. Some should receive medical diagnosis and treatment.

The normal loss of "dead cells" from the scalp is usually imperceptible or nearly so. The cells of the epidermis (outer skin layer) of the scalp are replaced about every 27 days; the "dead" cells scale off as they are replaced by new cells. Usually, not enough cells are shed at any one time to become noticeable.

Scalp scaling becomes noticeable, and an embarrassing problem, when something happens to (1) increase the rate of turnover in scalp epidermal cells, or (2) increase the size of shed flakes, as when increased scalp oiliness causes dead cells to adhere together into clumps.

The most common, and usually unprogressive, type of scalp scaling, pityriasis (shedding of bran-like flakes) is a slight increase in turnover of epidermal cells, with or without an increase in scalp oiliness (seborrhoea). At various times there have been suggestions that this mild form of pityriasis is associated with micro-organisms on the scalp-specifically a yeast Pityrosporum ovale. This has never been definitively established. Mild pityriasis can usually be managed with regular shampoos about once a week. The use of anti-dandruff shampoos is more successful for some persons than for others. If the flake-shedding is successfully managed, there is no need to consult a physician.

Many of the other conditions that cause scalp scaling require medical diagnosis and treatment. Some of the causes are manifestations on the scalp of systemic diseases such as psoriasis or hormonal dysfunction. The size, form and colour of the scalp scales can suggest a diagnosis. For example:

• Pityriasiform (bran-like) flakes are characteristic of mild pityriasis or "dandruff".
• Brittle flakes in several loose layers suggest psoriasis.
• A fish-scale form suggests the skin disease ichthyosis.
• Lichenoid scales suggest a skin disease such as lichen planus.
• Waxy, greasy, yellowish-brown scales suggest a seborrhoea.

Abnormally heavy scaling, excessive scalp oiliness, open lesions on the scalp, and unrelieved scalp itching are all indications to consult a physician.

Itching of the scalp can occur with any of the conditions that cause scalp scaling. Other causes of scalp itching include:

Contact dermatitis - irritation or allergic reaction associated with contact with an offending agent such as hair bleach, colouring solution, or permanent wave solution.

Eczema occurring on the scalp; the type of eczema called atopic dermatitis is a systemic disease requiring medical diagnosis and treatment.

Acne on the scalp.

Lichen simplex, a localised thickening and "itchiness" of skin caused by persistent rubbing or scratching of apparently normal skin.

Head lice.

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