There are many conditions where physical damage to the hair fiber results in hair loss. Sometimes hair fiber is damaged due to the hair being improperly formed by the hair follicles. These conditions are usually determined by genetic defects. There are also conditions where physical damage of the hair fiber is caused by something environmental, most often poor or inappropriate hair care.
Hair loss as a result of physical hair defects are rare compared to other causes of alopecia, but the most common ones are listed below.
Loose anagen syndrome or loose hair syndrome involves exactly what the name suggests, growing hair that is "loose" and easily pulled out of the hair follicle. Loose anagen syndrome is most often first diagnosed in young children, more so in girls than boys. Their hair never seems to grow, they rarely need a hair cut, and the scalp hair is usually thin, especially at the back of the scalp.
That the hair is loose and easily pulled out helps explain why the back of the head is most affected. The repeated rubbing of a person's head on a pillow at night pulls out more of the hair on the back of the head, whereas the front of the scalp has less contact with the pillow and so the hair is more likely to remain in place. The remaining hair usually does not grow very long and it can be unruly and difficult to comb and style.
Blond-haired children ages 2 to 5 are most likely to be affected but loose anagen syndrome can appear later in life as well. The syndrome improves with age of its own accord in children, but development in older individuals indicates the hair loss will be more persistent.
Why the hair is loose is not known, but the root sheaths that normally surround and protect the hair shaft in the skin are not produced properly in people with loose anagen syndrome. As a result, there is a lack of adhesion between the hair shaft and the root sheath, and the hair fiber is poorly anchored in the follicle.
There may be a genetic problem behind the syndrome and the condition can run in families, but there are also many isolated case reports with no family history. There are no known effective treatments for loose anagen syndrome.