Atopic dermatitis is an allergic condition that is characterized by dry, itchy skin. It is common in infants and children and can be accompanied by rhinitis or asthma.
One major sign of atopic dermatitis is itchiness which worsens at night. Scratching the itchy area on the skin can cause inflammation as well as infection. Another sign of atopic dermatitis is thick, leathery skin as the itchiness fades away.
An exact cause of atopic dermatitis has not been found yet, but scientists predict that this skin condition can occur due to various causes, including genetic factors.
Interestingly, family history also plays a role in the cause of atopic dermatitis. The likelihood of developing atopic dermatitis is higher if both parents have had atopic dermatitis than that of developing the condition when only one of the parents have had atopic dermatitis.
Then which gene from the parents is responsible for increasing the likelihood of developing atopic dermatitis? Before diving into the deep knowledge of genetics, let's first look at the immune response of the skin.
Immune system protects our body from antigens and other irritants that could potentially cause harm.
Immune responses are regulated by T-cells. The number of Th2 (T-helper type 2) and Th22 (T-helper type 22) cells are significantly increased when our skin encounters antigens. Both Th2 and Th22 cells have genes named IL-13 and IL-22, which is responsible for producing cytokines. Cytokines are proteins that are produced and released by immune cells. Immune cells then release the cytokines into the extracellular space, which then promotes other immune responses until the antigen is eliminated. Inflammation occurs on places where normal immune responses occur. After getting rid of the antigen, the inflammation as well as the immune response dies down, and the skin tissue is regenerated.
Things are different for patients with atopic dermatitis. Their immune system cannot be regulated normally and can respond to materials and substances that normally should not be considered as antigens. Also, the immune response towards antigens can be excessive. These excessive responses of atopic dermatitis patients can be due to genetic factors.
Genetic mutations have been discovered in atopic dermatitis patients. Mutations in IL-13 and IL-22 genes causes excessive production of cytokines. Cytokines are meant to promote immune responses toward antigens, but an excessive amount of cytokines can cause immune responses towards other materials, such as dust and pollen, that normally should not be considered as antigens in our body. This excessive production of cytokines then triggers itchy skin and the urge to scratch. Scratching only worsens the problem. Constant scratching prevents our skin from recovery and can lead to chronic atopic dermatitis, resulting in leathery patches.
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