Sudden "alopecia areata"? Learn the truth about alopecia areata

Author: Wu Yan, Chief Physician, Peking University First Hospital

Reviewer: He Yanling, Chief Physician, Beijing Chaoyang Hospital, Capital Medical University

Alopecia areata is a common skin disease that is characterized by sudden onset and localized hair loss, which often catches people off guard. In the folk, alopecia areata has a more vivid nickname - "alopecia areata". The sudden onset of this disease does give people a mysterious feeling, as if some invisible force shaved off part of the hair overnight. As one of the common diseases in dermatology, the occurrence mechanism, influencing factors, type classification and diagnosis methods of alopecia areata are worth our in-depth understanding.

Alopecia areata, also known as circular alopecia in medicine, is a local immune disorder. Although its mechanism of occurrence has not yet been fully clarified, studies have shown that alopecia areata occurs due to abnormal attacks on local hair follicles by immune cells. This abnormal immune response causes the hair follicles to quickly enter the resting phase from the normal growth phase, thus causing hair loss. The hair loss area is usually round or oval with clear boundaries, and sometimes a small amount of short new hair can be seen at the edge, which is called "exclamation mark-shaped" hair.

Figure 1 Original copyright image, no permission to reprint

The mechanism of alopecia areata is complex and diverse. In addition to abnormal reactions of the immune system, emotional factors are also generally considered to be one of the important causes. In modern life, young people face many challenges, such as staying up late, mental stress, and high work pressure. These mental stress states will have a negative impact on the immune system, causing the immune system to mistakenly identify normal hair as "foreign matter" and attack it. In addition, autoimmune diseases, unreasonable weight loss, and insufficient nutrition intake may also cause alopecia areata.

Alopecia areata can be divided into several types according to the different scope and degree of hair loss. Among them, the most common type is common alopecia areata, that is, one or more patches of hair loss appear on the scalp. When the hair loss extends to the entire scalp, causing all hair to fall out, it is called alopecia totalis. If the hair loss is not limited to the scalp, but also affects other hairy parts such as eyebrows, eyelashes, and armpits, it is called alopecia universalis. Alopecia totalis and alopecia universalis are the two most serious types of alopecia areata, which are more difficult to treat and have a higher probability of recurrence.

The severity of alopecia areata is mainly divided according to the scope of hair loss. Alopecia areata with a smaller area, such as the size of a fingernail, often has a milder immune response, and most patients can heal on their own. However, when the area of ​​hair loss exceeds the size of a palm, the possibility of alopecia areata healing on its own is significantly reduced, and timely medical treatment is required.

Figure 2 Original copyright image, no permission to reprint

When distinguishing alopecia areata from other hair loss diseases, we need to pay special attention to the difference between it and pseudo-alopecia areata (also known as scarring alopecia). Pseudo-alopecia areata is the result of a severe inflammatory response on the scalp that causes permanent damage to the hair follicles, which means that new hair will no longer grow in the affected area. There are obvious differences in appearance between alopecia areata and pseudo-alopecia areata. The scalp of patients with alopecia areata looks normal, without obvious redness, swelling, scarring or atrophy; while the scalp of patients with pseudo-alopecia areata may be accompanied by redness, dilation of capillaries or scarring.

In order to accurately diagnose alopecia areata and rule out other possible diseases, doctors usually ask patients to undergo a series of tests. The test items mainly include immune system indicators (such as autoantibodies, immunoglobulins, erythrocyte sedimentation rate, etc.), thyroid function, and blood routine tests to rule out other potential diseases. Through these tests, doctors can more accurately determine the cause of alopecia areata and develop targeted treatment plans.

In addition, the doctor may also use dermoscopy to observe the details of the hair loss area, such as the state and distribution of hair follicles. For difficult cases, a skin biopsy may be required to determine the cause through pathological analysis of tissue samples.