The differential of hair loss includes:
ALOPECIA AREATA - an autoimmune reaction to hair follicles. The diagnosis is made on the pattern of hair loss, such as smooth patches with short, broken-off hairs around the borders. Biopsy (the removal of a sample of tissue for study) is usually not necessary. Alopecia areata is a skin condition that causes the sudden loss of patches of hair on the scalp and sometimes other parts of the body. It is nonscarring, which means that there is no permanent damage to the hair follicle. In most patients, new hair eventually grows back in the affected areas, although this process can take months. Approximately 80 percent of people with mild alopecia areata recover within a year; however, the majority will experience more than one episode during their lifetime. There are treatments available (from creams to steroid injections) to speed hair regrowth and can be given at a dermatologists office. Other conditions may be associated with alopecia areata; these include vitiligo (a pigmentation disorder that causes patchy whitening of the skin), thyroiditis (inflammation of the thyroid gland), and pernicious anemia (a decrease in the number of red blood cells due to a vitamin B12 deficiency). Patients diagnosed with alopecia areata should be screened for these. More info at www.naaf.org
TINEA CAPTITIS — Tinea capitis is a fungal infection that causes itching, scaling, and irritation of the scalp, as well as breakage of the scalp hairs. The patches of hair loss in alopecia areata are distinguished from tinea by the smooth appearance and lack of scaling.
TRICHOTILLOMANIA — A small percentage of the population is affected by trichotillomania, or compulsive hair pulling. This produces areas of broken hairs of varying length; the resulting patches have a rough feel compared to the smooth patches of hair loss in alopecia areata. Obiviously your sister would know if this was the cause.
CICATRICAL ALOPECIA — Cicatricial alopecia, or scarring hair loss, can be caused by a number of rare disorders. In cicatricial alopecia, the hair follicle is permanently destroyed and replaced with scar tissue, so the hair cannot grow back.
TELOGEN EFFLUVIUM — Telogen effluvium is the most common cause of diffuse hair loss. The disease results in reversible diffuse loss of mature, terminal hairs, usually following a significant stressful event. Common triggers include pregnancy, severe weight loss (including with dieting), major illnesses and surgery, and traumatic psychological events.
ANDROGENETIC ALOPECIA — The most common type of hair loss is androgenetic alopecia, or "male pattern baldness". This condition involves a gradual thinning of the hair, rather than the sudden and patchy hair loss characteristic of alopecia areata. This is the most common cause of hairloss, and affects up to 40% of men and women. Women usually start hair loss before 40, and worsens after menopause. Although most women with androgenetic alopecia are endocrinologically normal, many have signs of androgen excess, such as menstrual irregularities, acne, excessive hair growth on face, or other signs of virilization. Given the frequency with which androgenetic alopecia occurs in women, an extensive hormonal evaluation is not necessary unless one of these signs or symptoms of androgen excess are present. Laboratory tests in women with suspected androgen excess should include total testosterone, dehydroepiandrosterone sulfate (DHEAS), and prolactin levels.
Hope this helps, in the meantime, I would recommend your sister see a dermatologist in her area.
M. M, MD