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HairlossTalk’s Science writer, Deborah O’Neil helps us understand Alopecia Areata a little better with this informative article.
A non-classical form of hair loss
In contrast to the gradual thinning seen in male and female pattern hair loss, the onset of alopecia areata (AA) is sudden and often extreme. This form of hair loss is the most spontaneous. A patchy, often random baldness can appear over the scalp within a staggeringly short space of time. Patients with AA commonly report finding handfuls of hair on their pillow or disappearing down the shower drain, without any prior clues or warning as to the onset of this relatively common hair loss condition, one that equally affects men and women.
The immune system is at fault
Scientific and medical research over the past few years has brought us much closer to understanding the cause of AA and it is now widely accepted that this form of hair loss is actually an autoimmune disease. This is a term given to any condition that results from the immune system targeting the body’s tissues, cells or organs, destroying them much in the same way as it would a bug (viruses and bacteria) or non-self, ‘foreign’ tissue. To date, we still do not fully understand why the immune system, which normally protects our body from infection and the onset of cancer, can turn against us in this way. Examples of common autoimmune diseases include rheumatoid arthritis, in which the soft tissue between the bone joints are destroyed and diabetes, where the insulin producing cells of the pancreas are destroyed. In AA, one or more component parts of the hair follicle appear to be the target for this inappropriate and self-destructive immune response, the result of which is the onset of one of the most insidious and upsetting forms of hair loss.
There are numerous triggers for AA, all of which combine with an already present ‘hard-wired’ genetic predisposition for the disease, to drive autoimmune mediated hair loss. These include hormonal changes induced during pregnancy or by contraceptive pills, various medications, stress, thyroid dysfunction, anemia, bacterial infections and other autoimmune diseases such as arthritis. These triggers will vary from individual to individual, but all act in an as yet undetermined way to cause an immune malfunction that results in the destruction of hair follicles over an area or areas of scalp. As upsetting as this sudden and extreme form of hair loss can be, the good news is that as with all relapsing-remitting autoimmune conditions, the hair will grow back once the trigger for the attack has been removed or the immune response that has caused is blocked.
A role for autoreactive lymphocytes
One wouldn’t normally expect to find many immune cells (the white cell component of blood in other words) within healthy scalp skin, as this area of tissue is relatively inert in terms of the need for a patrol of infection-fighting cells. In contrast, a number of investigators have reported finding numerous immune cells within skin samples obtained from the scalps of patients affected by AA. One cell type in particular, the T lymphocyte, is particularly abundant in these cases.Moreover, these cells are undoubtedly in an activated, immunogenic state. A 2002 study by Yano et al demonstrated that levels of cutaneous lymphocyte-associated antigen (CLA), a specific homing factor that recruits activated T-lymphocyte cells into the skin, correlate with AA disease activity. That is to say, blood taken from patients with severe or progressive AA have contains significantly higher levels of CLA (bound to T-lymphocytes) compared to blood samples derived from normal individuals or even AA patients recovering from the disease. CLA levels in AA patients who do not respond to oral corticosteroid therapy remain higher than in those who respond well to the treatment. In addition to this study’s findings from the patients blood, they also examined the distribution and levels of CLA within scalp skin and found high numbers of CLA bound to T-lymphocytes present around the hair follicles. These data suggest that CLA-positive T-lymphocytes may play an important role in AA and that a simple blood test may be used to monitor AA disease activity by assessing CLA levels.
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