This review presents a systematic approach to the diagnosis of hair loss. An accurate diagnosis is based on history, clinical examination, laboratory tests, and scalp biopsy. Whether the hair loss is a cicatricial or noncicatricial alopecia guides one’s history taking. After assessing the patient’s global appearance, the hair and scalp are evaluated, aided by a hair pull, hair tug, Hair Card, and hair mount. Scalp biopsies can confirm a diagnosis and are essential in all cases of cicatricial alopecia. In all patients with hair loss a complete blood count, ferritin, thyroid stimulating hormone, and vitamin D 25OH should be ordered.
Key Points
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At the start of the interview, evaluate for the presence or absence of follicular orifices, because history taking will be guided by whether the problem at hand is a noncicatricial or cicatricial alopecia.
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Determine whether the main issue is hair coming out “by the roots” or whether hair breakage is the main problem, because this will also guide the direction of history taking.
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For the clinical examination, position the patient with a hair problem in a chair, not on the examination table, to see the hair and scalp from above, and use magnified lighting from a close light source such as a portable magnifying lamp or a dermatoscope; daylight from a window or a lamp on the ceiling is not sufficient for the hair and scalp examination.
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The Hair Card, a 3 × 5-inch card, white on one side and black on the other, with a centimeter ruler along one edge, demonstrates new hair growth and miniaturized hair, and differentiates new hair from broken hair; the ruler portion is used for measuring length of new growth, temporal recession, and dimensions of hair loss.
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A scalp biopsy is the essential first step if a cicatricial alopecia is suspected, taken at or just beyond an active area of inflammation where hairs are still present, not a bare area.
Introduction
The hair follicle cycle is key to understanding hair loss because all causes of hair loss affect the hair cycle in some manner. The anatomic site of hair determines its size, and the diameter is determined by the size of the matrix. The 3 main phases of the hair follicle cycle include: (1) anagen or growth phase, which lasts 2 to 6 years; (2) catagen or involution phase, which lasts 2 to 3 weeks; and (3) telogen or resting phase, which lasts 2 to 3 months. The duration of anagen determines the hair length.
Hair follicles grow in a nonsynchronized fashion. Approximately 85% to 90% of scalp hair follicles are in anagen, 10% to 15% in telogen, and fewer than 1% in catagen. Scalp hair grows approximately 0.35 mm/d or 1 cm/mo. With 100,000 to 150,000 hairs on the scalp, the daily output of hair keratin protein is an impressive 35 m (0.35 mm/d × 100,000 hairs). Average normal daily scalp hair loss in an adult is 40 to 100 hairs on a nonshampoo day and 200 to 300 hairs on a shampoo day. Each hair that is shed is replaced by a new hair.
Introduction
The hair follicle cycle is key to understanding hair loss because all causes of hair loss affect the hair cycle in some manner. The anatomic site of hair determines its size, and the diameter is determined by the size of the matrix. The 3 main phases of the hair follicle cycle include: (1) anagen or growth phase, which lasts 2 to 6 years; (2) catagen or involution phase, which lasts 2 to 3 weeks; and (3) telogen or resting phase, which lasts 2 to 3 months. The duration of anagen determines the hair length.
Hair follicles grow in a nonsynchronized fashion. Approximately 85% to 90% of scalp hair follicles are in anagen, 10% to 15% in telogen, and fewer than 1% in catagen. Scalp hair grows approximately 0.35 mm/d or 1 cm/mo. With 100,000 to 150,000 hairs on the scalp, the daily output of hair keratin protein is an impressive 35 m (0.35 mm/d × 100,000 hairs). Average normal daily scalp hair loss in an adult is 40 to 100 hairs on a nonshampoo day and 200 to 300 hairs on a shampoo day. Each hair that is shed is replaced by a new hair.
Evaluating the patient
History
At the start of the interview, evaluate for the presence or absence of follicular orifices. Whether the problem at hand is a cicatricial (scarring) or noncicatricial alopecia guides history taking. The majority of this discussion focuses on noncicatricial alopecia, which accounts for most problems concerning hair loss.
Box 1 outlines the key features of history taking. Early in the interview, attempt to differentiate whether the hair is coming out “by the roots” or whether hair breakage is the issue. If the hair is coming out by the roots, ask whether the main concern is increased shedding or increased thinning. The patient’s medical history, particularly 6 to 12 months before the onset, may be relevant for increased shedding; for example, febrile illnesses, hospitalizations, surgeries, and traumatic events. Inquire about a family history of the same type of condition (androgenetic alopecia or alopecia areata) or associated conditions (family history of autoimmune diseases in alopecia areata). In a patient with androgenetic alopecia, ask about thinning hair in each family member. Ask patients whether they eat a balanced diet and, if they are vegetarian, ask the source of their dietary protein. Hair is composed of approximately 98% keratin protein, and the average adult produces approximately 35 m of hair keratin protein per day (0.35 mm/d × 100,000 hairs), which emphasizes the importance of daily protein intake.
Age of onset
Duration
Is hair coming out by the roots or is it breaking?
Increased shedding or increased thinning?
Medications
Past health
Family history
Diet: is there adequate protein or iron intake?
Menses, pregnancies, menopause
Hair care/hair cosmetics
Occupation and hobbies
In female patients, assess menses, pregnancies, and menopause. Does she have a menstrual period every month, for how many days, and how heavy is her menstrual flow? Does she have a history of infertility or miscarriages? Postpartum effluvium occurs 1 to 3 months after delivery, but does not necessarily occur after every pregnancy in a given patient. With menopause, hormone replacement with progestins that have androgenic metabolites, or testosterone, may aggravate or cause hair loss, as does removal of both ovaries.
Hair coming out by the roots
Common causes of hair coming out by the roots are shown in Box 2 . Distinguish whether there is increased shedding or increased thinning. Interest is focused on increased shedding that involves excessive hair drop-out on nonshampoo days. The sudden onset of markedly increased hair shedding is typical of telogen effluvium, and may last up to 6 months. In contrast, increased thinning implies less and less coverage and a more visible scalp, and may not be associated with increased shedding. Keep in mind that hair density has to decrease by more than half before there is noticeable hair thinning ( Fig. 1 ). Increased thinning is typical of androgenetic alopecia and age-related thinning.
Telogen effluvium
Alopecia areata
Androgenetic alopecia
Hair loss due to oral contraceptives
While taking oral contraceptives
After stopping oral contraceptives
Syphilitic alopecia
Oral contraceptive pills (OCP) may cause hair loss either while taking the OCP or after stopping the OCP. Taking progestins with androgenic metabolites, or testosterone, may cause increased thinning, particularly in women predisposed to androgenetic alopecia. Hair loss after stopping OCP can simulate postpartum effluvium and can occur after stopping any OCP.
Sometimes it is difficult to assess a patient’s concern about shedding, and in this situation hair collections are used. Ask patients to collect all hairs shed on a nonshampoo day, from the time they wake up until bedtime, and to place the hairs in a plastic bag that is dated. Collections are repeated once every 2 weeks over an 8-week period, and the 4 collections mailed to the clinician. The patient’s hair length must be documented ahead of time so that the volume of hair collected can be properly assessed. On a nonshampoo day, average daily hair loss is 40 to 100 hairs and on a shampoo day, 200 to 300 hairs. Do not count the hairs but rather make a visual estimate of each day’s collection.
Hair breakage
Increased hair breakage implies increased hair fragility. The Hair Card, discussed later in this article, demonstrates whether the distal ends are tapered, as with new growth ( Fig. 2 ), or whether they are blunt or straight, which indicates hair has been cut or broken ( Fig. 3 ). Common diagnoses associated with hair breakage are noted in Box 3 . The hallmark of tinea capitis is scalp scaling in an area of hair breakage. When tinea capitis is suspected, ask if schoolmates or other family members (such as grandmothers!) are affected. Trichotillomania, on the other hand, is not the result of innate fragility but rather of an extrinsic cause of hair breakage, such as a patient pulling or breaking hair. Hair-care practices and use of hair cosmetics do not cause significant hair breakage when carried out properly and according to directions. However, when done improperly they can cause damage and breakage. Examples of improper hair care practices include excessive heat used too frequently; bleaching, chemical relaxers, and permanent waves that are left on too long, or used too frequently; or chemical relaxers and permanent waves applied on the same day as hair coloring. Some individuals undoubtedly have a greater susceptibility to breakage than others.
