Nonscarring diffuse hair loss

Anagen effluvium (caused by agents that impair or disrupt the anagen cycle)

Chemotherapeutic agents

Poisoning (eg, thallium, arsenic, other metals)

Radiation (also causes scarring focal hair loss)

Androgenetic alopecia (male-pattern or female-pattern hair loss)

Androgens (eg, dihydrotestosterone)

Familial

Pathologic hyperandrogenism (virilization in females—see Hirsutism)

Polycystic ovary syndrome

Congenital disorders

Congenital atrichia with papules

Ectodermal dysplasia

Primary hair shaft abnormalities

Easy hair breakage (trichorrhexis nodosa)

Genetic disorders

Loose anagen hair syndrome

Overuse of hair dryers (bubble hair)

Telogen effluvium (increased number of hairs entering resting phase)

Endocrine problems (eg, hyperthyroidism, hypothyroidism)

Physiologic or psychologic stress (eg, surgery, systemic or febrile illness, pregnancy)

Alopecia areata

Diffuse loss of scalp hair (less common form of alopecia areata)

Alopecia totalis (complete scalp hair loss)

Alopecia universalis (complete scalp and body hair loss)

Systemic lupus erythematosus

Commonly causes diffuse hair loss

Nonscarring focal hair loss

Alopecia areata

Patchy loss of scalp hair (most common form of alopecia areata)

Ophiasis (band pattern hair loss along periphery of temporal and occipital scalp)

Sisaipho (central hair loss, sparing the hairs at the margin of the scalp)

Other

Hair loss due to compulsive hair pulling, twisting, or teasing (trichotillomania)

Postoperative (pressure-induced) alopecia

Primary hair shaft abnormalities (can also cause nonscarring diffuse alopecia)

Secondary syphilis

Temporal triangular alopecia

Tinea capitis*

Microsporum audouinii

Microsporum canis

Trichophyton schoenleinii

Trichophyton tonsurans

Traction alopecia*

Traction due to braids, rollers, or ponytails (occurs primarily at frontal and temporal hairlines)

Scarring hair loss (focal or diffuse)

Acne keloidalis nuchae

Folliculitis on the occipital scalp that results in scarring alopecia

Central centrifugal cicatricial alopecia

Progressive scarring alopecia on the crown or vertex of the scalp

Most common cause of alopecia in Black patients, typically occurring in women of African descent

Chronic cutaneous (discoid) lupus

Discoid lupus lesions of the scalp

Dissecting cellulitis of the scalp

Boggy inflammatory nodules that coalesce with sinus tract formation

Part of the follicular occlusion tetrad†

Lichen planopilaris and frontal fibrosing alopecia

Typically perifollicular erythema and follicular hyperkeratosis

Frontal fibrosing alopecia, a variant of lichen planopilaris, characterized by hair loss and scarring in the frontal region of the scalp

Secondary scarring alopecias

Burns

Morphea (localized scleroderma)

Progressive systemic sclerosis (scleroderma)

Radiation therapy (also causes nonscarring diffuse hair loss)

Sarcoidosis

Skin cancer

Superinfected kerion (due to severe primary syphilis or severe tinea capitis)

Trauma