Nonscarring diffuse loss: Causes include male-pattern baldness, female-pattern baldness, telogen effluvium, anagen effluvium, primary hair shaft abnormalities, and congenital disorders.
Male-pattern baldness (androgenetic alopecia) is common, familial, and androgenetic. Hair loss begins at the temples and/or vertex and can spread to diffuse thinning or nearly complete loss. Female-pattern baldness is hair thinning in the frontal, parietal, and crown regions. This too is androgenetic.
Alopecia (Female Pattern)
Telogen effluvium refers to loss of scalp hair caused by synchronicity of hair cycle so that many hairs enter the resting or telogen phase at once. At the end of this resting phase, usually several months after the inciting event, a significant increase in hair shedding is noticed. Drugs are a common cause, especially antiproliferative chemotherapeutic agents, warfarin.
Other drugs that can precipitate telogen effluvium are fluorobutyrophenone, clofibrate,bezafibrate, trimethadione , valproate, captopril, penicillamine, ibuprofen,interferon, ranitidine, sulindac, tamoxifen, terfenadine, and thiamphenicol.
Telogen effluvium is also common with nutritional deficiencies, after physiologic or psychologic stress (surgery, systemic illness), and with pathologic (hypothyroidism or hyperthyroidism) or physiologic (postpartum, menopause) endocrine changes.
Anagen effluvium refers to loss of scalp hair in its growth (or anagen) phase. Radiation and chemotherapeutic agents are the most common causes, but it can occur with mercury, thallium, boric acid, and vitamin A poisoning.
Primary hair shaft abnormalities (trichodystrophies) include a variety of disorders that lead to unruly or unusually wooly hair or to fractures of the hair shaft. In trichorrhexis invaginata, hairs have a ball and cup invagination (bamboo hair). This hair abnormality can occur in association with ichthyosis in the rare autosomal recessive Netherton syndrome. Bubble hair, in which bubbles are seen in the hair shaft, may occur with excessive use of hair dryers. Trichonodosis or knotting of hair occurs with excess rubbing or scratching. Monilethrix is an uncommon autosomal dominant condition that causes beaded and very brittle hair.
Other congenital disorders of the hair include wooly hair nevus (tightly coiled hair over all or portions of the scalp), the uncombable hair syndrome (scalp hair that resists all efforts to comb or brush it), trichorrhexis nodosa (hair shafts break easily and broken stumps are present over large portions of the scalp), and trichothiodystrophy (brittle hair from a defect in sulfur metabolism).
Nonscarring focal loss: Common causes include traction alopecia, tinea capitis, trichotillomania, and alopecia areata (see Hair Disorders: Alopecia Areata). Uncommon causes include syphilis and primary hair shaft abnormalities.
Traction alopecia is hair loss primarily at the frontal and/or temporal hairline due to traction from braids, rollers, or ponytails. Tinea capitis, hair shaft infection with Trichophyton tonsurans, is discussed in Fungal Skin Infections: Tinea Capitis; other less common causes of tinea capitis include Microsporum canis , M. audouinii, and T. schoenleinii. Trichotillomania—focal hair loss due to hair pulling, twisting, or teasing—is symptomatic of an obsessive-compulsive disorder (see Anxiety Disorders: Obsessive-Compulsive Disorder (OCD)).
Late secondary syphilis causes hair loss ranging from localized patches to total alopecia. It may follow the distribution of the preceding exanthem. The serology is always positive. Examination reveals focal yellow-red areas with a moth-eaten appearance.
Scarring focal loss: Scarring refers to obliteration of the hair follicle with fibrosis. Scarring loss is most often due to unusual primary disorders, such as lichen planopilaris (lichen planus of the scalp), folliculitis decalvans (an idiopathic scarring alopecia associated with pustules and intact hairs clumped in a “tufted” pattern), and pseudopelade of Brocq (a particular pattern of scarring alopecia). Other causes include burns, trauma, radiation therapy, severe primary (kerion) or secondary (syphilis) infections, sarcoidosis, lupus erythematosus, and skin malignancy.Nuestros socios: tratamiento impotencia tratamiento eyaculacion
