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Alopecia areata

life science Maturity 11-13 Next article →

Alopecia areata, often called spot baldness, is a medical condition characterized by hair loss.

Alopecia areata
Alopecia areata

This loss can affect small areas or the entire body. It most commonly appears as smooth, round, or oval bald patches on the scalp. These patches are often about the size of a coin. While it most frequently affects the scalp and beard, it can occur anywhere hair grows. The condition is classified as a type 1 inflammatory disease. It is not contagious, meaning you cannot catch it from someone else.

The condition is believed to be a systemic autoimmune disease. In a healthy body, hair follicles enjoy something called immune privilege. This means the immune system is trained to ignore these specific cells. In alopecia areata, this privilege is breached. The body fails to recognize its own hair follicle cells as safe. Consequently, immune cells called T-lymphocytes swarm the hair roots. This process causes inflammation and destroys the anagen, or growing, hair follicles.

Alopecia areata
Alopecia areata

This immune-mediated destruction causes the hair to fall out.

There are several ways to classify the severity of the hair loss. Alopecia areata monolocularis describes hair loss in only one single spot. If there are multiple areas of loss, it is called multilocularis. Some patients experience ophiasis, which is hair loss shaped like a wave around the head's edge. If a person loses all the hair on their scalp, it is called alopecia totalis. In the rarest cases, a person loses all body hair, including pubic hair. This most severe form is known as alopecia universalis.

Fox Plate V
Fox Plate V

Research suggests that genetics play a significant role in who develops the condition. Having a family history of alopecia areata increases a person's risk. For example, if one identical twin is affected, the other has a 50% chance of being affected. Scientists have identified at least four regions in the genome linked to these risks. A large study in 2010 identified 129 single nucleotide polymorphisms associated with the disease. These genetic markers involve cells that control T-cell activation and various proteins like interleukin-2. The condition also shares genetic risk factors with other autoimmune diseases like type 1 diabetes and celiac disease.

Statistics show how common the condition is across the population. At any single moment, about 0.15% of people are affected. However, about 2% of people will experience the condition at some point in their lives. Onset usually occurs during childhood, and females are affected at higher rates than males. For many, the disease is temporary. In over 50% of cases involving sudden, patchy hair loss, hair regrows within one year. For those with only one or two patches, the recovery rate within a year is as high as 80%. However, for those with alopecia universalis, fewer than 10% recover.

Doctors look for specific clinical signs to diagnose the condition. One notable sign is "exclamation point" hairs. These are very short hairs that are narrower at the base than at the top. They often surround the edges of bald patches. During a physical exam, doctors might notice that hair pulls out more easily at the edge of a patch. This happens because the immune system is actively attacking the follicles there. In some cases, a doctor might use trichoscopy to look for "yellow dots" or "black dots" in the follicles. Some patients may also experience nail changes, such as pitting or trachyonychia.

While there is currently no cure, several treatments can help manage the condition. Some treatments aim to speed up hair regrowth. For instance, a 2020 review showed that 5 mg/mL triamcinolone injections helped over 80% of patients achieve more than 50% regrowth. Topical 5% minoxidil is also used to encourage growth. In 2022, the FDA authorized baricitinib, a Janus kinase (JAK) inhibitor, for severe cases. If the hair loss is linked to celiac disease, following a gluten-free diet can sometimes lead to permanent regrowth. This happens because removing gluten helps normalize the body's immune response.

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File:Fox Plate V.jpg
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