13: Diffuse hair loss

Abstract:

Hair loss is frequently very distressing to patients. Hair loss is divided into scarring hair loss and nonscarring hair loss. This chapter discusses conditions that can cause diffuse hair loss. These include androgenetic alopecia, lichen planopilaris, telogen effluvium, and alopecia areata.

Key terms:

androgenetic alopecia

alopecia universalis

alopecia totalis

lichen planopilaris

telogen effluvium

Androgenetic alopecia

Clinical features

Androgenetic alopecia (AGA; also known as “female-pattern hair loss” and “male-pattern baldness”) is the most common type of hair loss in both men and women. It is caused by androgen-mediated effects on hair follicles, which result in miniaturization of hairs, decreased hair count, and observable hair thinning in a male-patterned scalp distribution.

• AGA presents differently in men and women and treatment differs, too.
- • In men, AGA presents with frontotemporal hairline recession and diffuse thinning of the crown of the scalp. Importantly, hair on the occipital and temporal scalp is never lost in AGA because the hairs in these areas are androgen insensitive.
  - • The first sign of AGA in men may be kinking of hairs in the frontotemporal scalp (Fig. 13.1), which causes these hairs to become increasingly difficult to style.
- • In women, AGA presents with thinning of the crown and frontal aspects of the scalp despite preservation of the frontotemporal hairline.
  - • AGA is less common in black women in whom central centrifugal cicatricial alopecia, a scarring hair loss affecting the crown of the scalp, is the most common form of hair loss.
• For men and women, AGA is characteristically asymptomatic, nonpatchy, lacking in overlying skin changes, and nonscarring, which helps to distinguish it from other causes of hair loss.
• Close examination, especially with a magnifying glass and bright light (trichoscopy or dermoscopy of the hair and scalp) of affected areas reveals hairs with varying widths, which is diagnostic for AGA.

Fig. 13.1 **Early Androgenetic Alopecia in a 26-Year-Old Male.** Note the decreased hair density and variability in hair shaft diameter.

Differential diagnosis

The differential for AGA is broad and includes telogen effluvium (TE), lichen planopilaris (LPP), traction alopecia, central centrifugal cicatricial alopecia (CCCA), and alopecia areata. Importantly, multiple types of hair loss can coexist in the same individual, making accurate diagnosis difficult in some cases.

• TE is a nonscarring alopecia characterized by diffuse shedding and thinning of the scalp. It is caused by hairs entering the telogen phase of the hair cycle prematurely. This typically presents 3 to 4 months after a significant illness, major stressor, or the initiation of a new medication. TE can be distinguished from AGA because it is characterized by diffuse, nonpatterned thinning of the scalp rather than the thinning characteristic of AGA. Furthermore, patients with TE report a significant increase in the amount of daily shedding that they experience. This shedding can be objectified by performing a pull test on unwashed hair; it is positive if more than 10 telogen hairs are removed by a gentle pull. TE is also typically more transient than AGA; however, chronic TE can occur.
• LPP is a scarring alopecia that is characterized by the presence of perifollicular erythema and scaling that progresses to scarring hair loss on the scalp vertex. A clinical variant of LPP, frontal fibrosing alopecia (FFA) presents with identical clinical findings to LPP; however, it affects the frontal scalp and causes marked recession of the hairline. LPP is distinguished from AGA because it is symptomatic (burning and itching), it presents with perifollicular erythema, and it scars. FFA should be considered in any woman with significant hairline recession because hairline recession is not frequently seen in AGA in women.
• Traction alopecia is a common type of nonscarring alopecia that can progress to scarring alopecia overtime. It is caused by tight hairstyling that chronically puts significant traction on the hair follicles. It is characterized by frontotemporal hair loss, almost exclusively in women, that demonstrates a positive fringe sign where the hairline appears grossly normal despite significant thinning of the hair directly behind it. Traction is distinguished from AGA by its characteristic distribution, history of tight hairstyling (especially braiding), and the absence of hair loss elsewhere on the scalp.
• CCCA is a common form of scarring alopecia that predominantly occurs in black women. It should be considered in all black women who present with AGA-like hair loss. It is characterized by progressive scarring of the vertex scalp in the absence of clear primary lesions. It can be differentiated from AGA because it scars.
• Alopecia areata is an autoimmune hair loss that frequently presents with discrete patches of hair loss. Typically, it is not misdiagnosed as AGA because it is very patchy, comes and goes, and occurs in areas that are not characteristic of AGA. Less common variants of AGA that affect the entirety of the scalp (e.g., alopecia totalis, alopecia universalis) can occasionally be mistaken for AGA. These variants can be distinguished from AGA based on their quick development, their distribution (which is beyond that which is typical for AGA), and their responsiveness to steroids.

Work-up

AGA is typically a clinical diagnosis; however, in some cases, additional work-up is required to distinguish it from mimickers.

• Examining distribution of hair loss is helpful in narrowing down the differential.
• In all patients, examination of hairs on an affected area with magnification can be helpful because AGA presents with easily appreciable variation in the diameter of hairs, which is not seen in other forms of hair loss.
• In cases where diagnosis is uncertain, punch biopsy can be helpful for securing a diagnosis. This should only be performed by an experienced healthcare provider because performing biopsies on the scalp is technically difficult.
- • The specimen must be sent to a dermatopathology lab that is experienced in processing scalp specimens because they are prepared differently than regular skin biopsies.
• Women with early-onset and/or severe AGA with other masculinizing features benefit from a hormonal work-up to evaluate for polycystic ovarian syndrome (luteinizing hormone [LH], follicle-stimulating hormone [FSH], dehydroepiandrosterone [DHEA], and free testosterone).

Initial steps in management

Management of AGA is different in men than it is in women. Regardless, early, aggressive management is recommended because maintenance of hair is much easier to achieve than hair regrowth.