Definition and Epidemiology

Alopecia is a term used to describe abnormal hair loss. There are varied causes of hair loss. Medications, chemotherapy, radiation therapy, diabetes, trichotillomania, and hair loss from hair dyes or hairdos are possible causes, but alopecia is also related to congenital hair abnormalities and the more commonly observed alopecia from androgenetic or pattern hair loss. Whatever the cause, hair loss is a disturbing and highly emotional issue for many patients.

Pathophysiology

Alopecia, except for congenital alopecia, can be divided into two types of alopecia: scarring (cicatricial alopecia) and nonscarring (noncicatricial alopecia).¹ In noncicatricial alopecia, the hair follicles are still present and there is no sign of inflamed tissue, scarring, or atrophy.¹ Alopecia areata, androgenetic alopecia, lupus erythematosus, syphilis, telogen effluvium, and tinea capitus are all potential causes of noncicatricial alopecia.² Cicatricial alopecia—scarring alopecia—is usually the result of an intense inflammatory process of the scalp, with resultant skin atrophy and scarring.¹ Chronic cutaneous discoid lupus, folliculitis decalvans, lichen planus, linear scleroderma, sarcoidosis, and cutaneous metastasis are potential causes of scarring alopecia.²

Each hair follicle goes through a highly programmed cycle over and over again throughout its life. The cycle of hair growth involves three phases: anagen, catagen, and telogen, which represent the growth, involution, and rest phases.¹ The anagen (growth) phase varies according to the location of the follicle on the body. This phase is longest on the scalp (producing long hairs) and much shorter on the eyebrows (producing short hairs). During the catagen phase, the hair involutes. This is the shortest of the three stages. During the telogen phase, the mature hair is shed, resulting in the loss of 50 to 150 scalp hairs each day.

Clinical Presentation

The history is a critical part of the evaluation of a person with alopecia. The provider should inquire about the onset, duration, and rapidity of the hair loss; any acute or chronic illnesses; current and past medications; and any symptoms that may be related to trichotillomania. It is important to determine whether the patient has had this type of hair loss before. Long and insidious hair loss is more indicative of androgenetic alopecia. Alopecia areata is often recurrent. An acute illness, such as a high fever, can trigger telogen effluvium, as can hyperthyroidism or hypothyroidism. A family history of hair loss may represent a clue for androgenetic alopecia, sometimes a hereditary disorder.

It is also important to inquire about associated symptoms. Scalp itching, pain, or flaking can suggest an inflammation of the scalp from psoriasis or contact dermatitis from hair dye. These conditions inflame the scalp and can cause hair breakage with resultant alopecia. In addition, symptoms of scalp itching and flaking can indicate tinea capitis, a fungal infection of the scalp that weakens the hairs and produces alopecia.

Physical Examination

The physical examination begins with an evaluation of the pattern of hair loss. Androgenetic alopecia in men usually is seen as recession of the hairline at the temples and thinning in the frontal areas and the vertex. Women with androgenetic alopecia usually have diffuse thinning that is most pronounced in the frontal and parietal areas. A rim of hair along the frontal hairline is usually preserved.

Alopecia areata usually is initially seen as well-demarcated patches of hair loss on the scalp, eyebrows, and eyelashes. Singular, “exclamation point” hairs are sometimes visible. These exclamation point hairs are normal distally but are thinned proximal to the scalp. The scalp is not inflamed in alopecia areata. Men may experience alopecia areata in the beard area. When the whole scalp is affected, the process is called alopecia totalis.⁵ If the whole body is involved, the process is called alopecia universalis.^5,6

Anagen effluvium tends to result in a diffuse loss of hair, as does telogen effluvium. Scarring of the scalp suggests an inflammatory process, such as lupus or lichen planus follicularis. Scaling on the scalp may suggest psoriasis or tinea capitis. Patchy hair loss with regrowing hairs of multiple lengths suggests trichotillomania, a condition in which the patient pulls or twists the hair.