The word "alopecia" is the medical term for hair loss. Alopecia does not refer to one specific hair loss disease -- any form of hair loss is an alopecia. The word alopecia is Latin, but can be traced to the Greek "alopekia," which itself comes from alopek, meaning "fox." Literally translated, the word alopecia (alopekia) is the term for mange in foxes.
Unlike alopecia, which describes hair loss where formerly there was hair growth, hypotrichosis describes a situation where there wasn't any hair growth in the first place.
Hair loss can be caused by any number of conditions, reflected in a specific diagnosis. Some diagnoses have alopecia in their title, such as alopecia areata or scarring alopecia, but many do not, such as telogen effluvium.
Alopecia can be caused by many factors from genetics to drugs. While androgenetic alopecia (male or female pattern baldness, AGA for short) is by far the most common form of hair loss, dermatologists also see many people with other forms of alopecia. Several hundred diseases have hair loss as a primary symptom.
Probably the most common non-AGA alopecias a dermatologist will see are telogen effluvium, alopecia areata, ringworm, scarring alopecia, and hair loss due to cosmetic overprocessing. Other, more rare forms of hair loss may be difficult to diagnose, and some patients may wait months, even years for a correct diagnosis and undergo consultation with numerous dermatologists until they find one with knowledge of their condition. Plus, with rare diseases, there is little motivation for research to be conducted and for treatments to be developed. Often, even when a correct diagnosis is made, a dermatologist can offer no known treatment for the condition.
Research into hair biology and hair diseases is a very small field, and even research on androgenetic alopecia is quite limited. Perhaps 20 years ago there were fewer than 100 people worldwide who studied hair research in a major way. In recent years, there may be five times as many. This is still a small number compared to, say, diabetes research, but the expanding numbers of researchers investigating hair biology is positive, and eventually should lead to a better understanding and more help for those with rare alopecias.
