Diseases Affecting the Hair

Diseases Affecting the Hair

Thelda M. Kestenbaum MD

Hair is an extremely important part of an individual’s appearance and sense of identity. Loss of hair on the scalp or an excessive amount of unwanted hair on other body parts causes great psychologic distress. Our perception of femininity and masculinity is greatly affected by hair quantity, hair distribution, and hair styling.

Hair Physiology

There are three types of hairs: lanugo, vellus, and terminal hairs. Lanugo hairs are long, unmedullated hairs seen in utero and are shed during the end of pregnancy and the first several months postpartum. Vellus (or intermediate hairs) are short, nonpigmented hairs produced by follicles that penetrate only into the papillary dermis. Terminal hairs are produced by follicles that penetrate into the reticular dermis and are usually medullated (have a medulla), and are wider than the inner root sheath of the follicle that produces them. Hairs on the scalp and beard area are examples of terminal hairs. In the inherited types of balding some terminal hairs are lost and vellus hairs are seen instead.

Hair growth is not a continuous process. There is an anagen (growth) phase (about 85% to 95% of scalp hairs), a catagen (regressive) phase (about 1% of scalp hairs), and a telogen (resting) phase (about 10% to 15% of scalp hairs). The length of the anagen phase determines the length of the hair.Human scalp hair anagen phase is usually between 2 and 6 years, and the hair on the scalp grows about 1 cm/month. Therefore, some people can never have very long hair on the scalp even if they never cut their hair. Growth phases of hair on other body parts are much shorter than on the scalp. It is normal to lose between 50 and 100 scalp hairs per day. Plucking the resting hairs from follicles that have already entered anagen can advance the onset of the next anagen phase. Shaving the hair has no effect on the hair cycle. The telogen phase is the period between the completion of follicular regression (catagen) and the onset of the next anagen phase. On the human scalp, telogen phase lasts about 2 to 4 months, whereas catagen phase on the human scalp lasts 2 to 4 weeks.

With aging or with the inherited type of hair loss there is a shortening of the anagen phase and a lengthening of time between telogen and a new anagen phase. Hair cycles are influenced by multiple factors such as the season and a change in hormonal status as seen in pregnancy. Seasonal changes in hair shedding are usually not noticeable but are important when conducting studies on treatment of hair loss. During pregnancy there is an increase in the proportion of follicles in anagen, and postpartum there is an increase in the proportion of hairs in telogen, which results in a marked increase in shedding usually 3 months (1 to 5 months) postpartum. This problem rectifies itself usually within a year or less.

Hairs vary in diameter and number in different racial groups. The diameter of Asian hair is the widest and is round in cross section. Caucasian hair is round to oval in cross section. Black hair is more elliptical or flattened in cross section; black hair follicles are spiral in shape. The volume of the hair papilla determines the size of the hair shaft.

Hair amount varies among races with Caucasians (especially those of southern European extraction) generally being hairier than other racial groups. The number of scalp hairs is 10% greater in blonds and 10% less in redheads compared to Caucasian brunettes. Blacks have significantly fewer hair follicles and more fragile hair than Caucasians.

Graying of the hair is a normal process of aging and develops in Caucasians about a decade earlier than in blacks. Graying earlier than 20 years of age is considered premature in Caucasians, and graying earlier than 30 years of age is considered premature in blacks. By 50 years of age, the average Caucasian is 50% gray. In Caucasians, the age of onset of graying varies from 24 to 44 years; in blacks from 34 to 54 years; and in Asians in the 30s. Premature graying has been associated with pernicious anemia as well as thyroid disease (usually hyperthyroidism, may be seen with hypothyroidism), and a host of unusual inherited syndromes. A frontal white patch of hair may be inherited as an autosomal dominant trait (piebaldism). People with alopecia areata may note regrowing hairs that are light in color. People who are said to have “turned gray overnight” probably are those with “salt and pepper” hair that developed a diffuse form of alopecia areata in which the dark hairs were lost preferentially to the gray hairs.

Many people color their hair. The most common chemical used to dye the hair is paraphenylenediamine, which is sometimes the cause of a contact dermatitis.

Hirsutism and Hypertrichosis

Hirsutism is the excessive growth of terminal hair in a male sexual pattern in a female or a child. Hypertrichosis is the hair growth that is abnormal for the age, gender, or race of an
individual or for a particular area of the body. Medications can cause either of these problems (Table 32-1).

TABLE 32-1 ▪ Drugs That Can Cause Hirsutism and Hypertrichosis



















The prevalence of hirsutism in women overall is said to vary from 5% to 15%. The most common diagnosis associated with hirsutism is polycystic ovary syndrome (PCOS). Overall, about 5% to 15% of cases of hirsutism are idiopathic, but about 50% of cases of mild hirsutism are idiopathic.

Asian and Scandinavian women are generally less hairy than Caucasian women of Mediterranean ancestry, so sometimes it is difficult to judge when the hair growth in women is abnormal. Also, menopausal women who are not on hormone replacement may note some hirsutism. Androgen excess and drug-induced hirsutism need to be ruled out. Laboratory tests should be guided by the history and physical examination. Certainly, other signs of virilization such as severe acne would lead one to do a more aggressive hormonal evaluation. In mild hirsutism, when menses are regular and there are no features to suggest other causes, holding off on further laboratory testing is reasonable.

If hirsutism is moderate or severe or there are features suggestive of a secondary cause, then androgen levels and ultrasonographic examination of the ovaries, adrenals, or both may be in order. Pelvic ultrasonography may be useful in establishing the diagnosis of PCOS. Plasma-free testosterone is 50% more sensitive than total testosterone for detecting androgen excess and is the best single indicator of hyperandrogenism. The most reliable method of establishing free testosterone is by computing it from the levels of total testosterone and the sex hormone binding globulin (SHBG). Finding a reputable laboratory for establishing this information is imperative.

In females with androgen excess, 1.5% to 2.5% have nonclassic congenital adrenal hyperplasia and 0.2% have androgen-secreting tumors (half of these tumors are malignant). Other causes of androgen excess include Cushing’s syndrome, hyperprolactinemia, acromegaly, and thyroid dysfunction. About 8% of hirsute women have idiopathic hyperandrogenism.

Sometimes a serum testosterone and 17-α-hydroxyprogesterone may be sufficient, but women with irregular menses and hirsutism should be screened for thyroid dysfunction and prolactin disorders. A dehydroepiandrosterone sulfate (DHEAS) test is useful for screening for adrenal tumors but is not reliable for screening late-onset congenital adrenal hyperplasia. The presence of striae, central obesity, and peripheral weakness make the diagnosis of Cushing’s syndrome possible where a 24-h urine free cortisol test would be indicated.

Normally 78% of the testosterone in women is bound to SHBG, only 1% to 2% is free (which is the bioactive portion), and 20% is bound to albumin. SHBG may be reduced in amount by obesity, hypothyroidism, and hyperinsulinemia, thereby increasing free testosterone levels and therefore possibly leading to hirsutism.

An early-morning follicular phase 17-α-progesterone level is one of the better tests to screen for congenital adrenal hyperplasia. There are some rare enzyme deficiencies that can lead to congenital adrenal hyperplasia that might be better treated by an endocrinologist.

PCOS has a prevalence of 5% to 10% in all women and is the most common diagnosis associated with hirsutism. Stein and Leventhal were the first to describe this syndrome of amenorrhea, obesity, and hirsutism in association with sclerocystic ovaries. PCOS may be better described as chronic anovulation and hyperandrogenism with the exclusion of androgen-secreting tumors, nonclassic adrenal hyperplasia, and hyperprolactinemia. Currently, PCOS is said to be characterized by the presence of two or more of the following: chronic oligo-ovulation or anovulation, androgen excess, and polycystic ovaries.Usually these women have hirsutism, irregular menses, acne, and alopecia.

Insulin resistance with compensatory hyperinsulinemia is a prominent feature in many but not all cases of PCOS. Prevalence of type 2 diabetes is 10 times the rate of normal women. In women with PCOS the prevalence of metabolic syndrome is two to three times the rate in normal women and it may be that the prevalence of fatal myocardial infarction (if oligomenorrhea is severe) may be double the rate of normal women. Commonly found laboratory abnormalities in PCOS include an elevated total testosterone (about twice the normal), an elevated luteinizing hormone (LH) level (at least twice the value for follicle stimulating hormone (FSH)), a slight elevation in prolactin, and a slight elevation in DHEAS. The PSA (prostate-specific antigen) test may or may not be helpful in distinguishing women with PCOS from those with idiopathic hirsutism.

Treatment of hirsutism involves finding the cause and obtaining the help of an endocrinologist in some cases. Oral spironolactone (Aldactone) may be helpful in PCOS and idiopathic hirsutism. Spironolactone interferes with androgen
biosynthesis, blocks the action of androgens at the receptor level, and decreases the 5-α-reductase levels in the follicle. Six months’ treatment of spironolactone at 100 to 200 mg/day is at least worth a trial. It is important that this should not be given to women who are not using adequate contraception since it is teratogenic (it is a pregnancy category D drug). Oral contraceptives, flutamide (not approved by the FDA), finasteride, and cyproterone acetate (this is an ingredient in the contraceptive pill called Dianette, which is not available in the United States) are some other treatments that are available. The use of the antihyperglycemic metformin does reduce markers of insulin resistance in PCOS, and this may help treat hirsutism. Eflornithine hydrochloride (Vaniqa) cream is an irreversible inhibitor of ornithine decarboxylase that slows (but does not remove hair) hair growth and has been approved by the FDA for treatment of facial hirsutism.Maximal effect is seen by 8-24 weeks of use with marked improvement in 32% of users (compared to 8% marked improvement in the placebo group). This drug is used systemically for treatment of African trypanosomiasis, and its side effect of hair loss has been utilized in the development of it as a cream for treatment of facial hirsutism. Removal of hair as discussed under treatment of hypertrichosis may be a helpful adjunct to treatments mentioned here.


Hypertrichosis is the hair growth that is abnormal for the age, gender, or race of an individual or for a particular area of the body. It may result from the conversion of vellus hairs to terminal hairs, more hairs being in a prolonged anagen (growth) phase (and therefore a decrease in the number of hairs in the telogen phase) or an increase in hair follicle density.

It may be helpful to divide hypertrichosis into congenital or acquired and then into generalized and localized types.

Congenital generalized hypertrichosis and congenital hypertrichosis lanuginosa both are very rare inherited disorders; “dog-faced” or “monkey-faced” people in circus sideshows may have had the former diagnosis. Congenital hypertrichosis may be a feature of numerous inherited syndromes such as mucopolysaccharidoses, leprechaunism, and Cornelia de Lange syndrome. Of particular note is that fetuses exposed to hydantoin (Dilantin) during the first 9 weeks of gestation may have hypertrichosis as part of the fetal hydantoin syndrome. Hypertrichosis may also be seen in fetal alcohol syndrome.

Congenital localized hypertrichosis over the vertebral column (faun tail) may be a marker of an underlying spinal abnormality. Magnetic resonance imaging is strongly recommended in such cases since the underlying problems may require early surgical intervention to prevent neurologic damage. Congenital hypertrichosis of the ears may be seen in the babies of diabetic mothers or in babies with XYY syndrome. Hairy elbows may be present at birth or acquired, and may or may not be associated with other abnormalities.

Acquired hypertrichosis may be generalized or localized. Generalized acquired hypertrichosis may be seen as acquired hypertrichosis lanuginosa (malignant down), which is a rare, but striking, marker of an internal malignancy (usually lung or colon cancer but a multiplicity of underlying tumors have been associated). Multiple normal hair follicles revert to lanugo hair usually starting on the face and progressing caudally. Generalized acquired hypertrichosis may occur in diverse conditions, including porphyrias, dermatomyositis, anorexia nervosa, mercury intoxication (acrodynia), insulin-resistant diabetes, hypothyroidism, posten cephalitis, multiple sclerosis, head injuries, and POEMS syndrome (Polyneuropathy, Organomegaly, Endocrinopathy, Monoclonal gammopathy Skin changes: hyperpigmentation, hypertrichosis, skin thickening, edema, digital clubbing, cutaneous angiomas, among other possible signs). Multiple drugs can cause hypertrichosis (see Table 32-1). Some cause generalized and some localized hypertrichosis. A newer drug in this latter category is one for treatment of glaucoma called latanoprost which is a prostaglandin F analogue that causes hypertrichosis and hyperpigmentation of the eyelashes in most (77%) patients using it. (Unfortunately, latanoprost was not helpful for treatment of eyebrow alopecia areata.)

Localized acquired hypertrichosis on the pinnae may be an inherited trait (especially in men from India), or it may be seen with diabetes or with acquired immunodeficiency syndrome (AIDS). Localized hypertrichosis may develop under orthopaedic casts, or in areas that are chronically traumatized such as lichen simplex chronicus (neurodermatitis), areas in which habitual self-inflicted biting occurs (dermatophagia), over thrombophlebitis or over areas of osteomyelitis.

Treatment of hypertrichosis may include shaving, depilatories, bleaching, plucking, waxing (a sort of plucking of multiple hairs simultaneously), laser, and electrolysis. Electrolysis may require more than one treatment and should be carried out by someone trained in the procedure and who uses sterile needles so as to prevent transmission of bloodborne disease. Shaving, contrary to popular belief, does not increase the amount of hair that regrows. Chemical depilatories and bleaching agents are available over the counter and frequently prove effective, but they may irritate the skin of some users.Waxing and plucking have the advantage of removing the unwanted hair for longer periods without retreatment than does shaving or chemical removal. Electrolysis can cause scarring and is expensive. Laser (usually 694 to 1064 nm wavelengths) may be helpful in selected cases but may cause scarring. Light-skinned women with dark hair are the best candidates for laser.

Alopecia (Hair Loss)

Alopecia of the scalp is of considerable concern to men and women. It is helpful in differentiating among the many causes of alopecia to examine the hair and scalp and observe whether the scalp is scarred or nonscarred and whether the hair loss is diffuse (the most common type) or
patchy (Table 32-2). Establishing whether the hair is coming out by the roots or breaking off will help guide the physician how to proceed with the workup. If the hair loss is scarring, a scalp biopsy early on will probably prove helpful. If the hair is breaking off, fungal infection, trauma, or hair shaft defects are more likely causes. Loss of up to one-half of the scalp hair may occur before the hair loss is clinically obvious on casual inspection.

TABLE 32-2 ▪ Nonscarring and Scarring Hair Loss

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May 28, 2016 | Posted by in Dermatology | Comments Off on Diseases Affecting the Hair
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Nonscarring Hair Loss


Androgenic* (female pattern; male pattern)

Telogen effluvium



Sudden weight loss



Endocrinopathy (hypothyroidism; hyperthyroidism)

Alopecia areata

Loose anagen syndrome


Tinea capitis

Alopecia areata



Traumatic (traction)

Loose anagen syndrome

Scarring Hair Loss


Trauma (traction)

Tumors (malignant or benign)

Skin diseases (such as sarcoid; scleroderma)


Central centrifugal cicatricial alopecia (CCCA)

Discoid lupus§

Lichen planopilaris

Frontal fibrosing alopecia

Pseudopelade of Brocq


Folliculitis decalvans

Dissecting cellulitis


Acne keloidalis