SNP Shot: Genomic Insights

Atopic dermatitis, also called atopic eczema, is a skin condition marked by inflammation (dermatitis). It typically starts in infancy and often resolves before adolescence. However, it can persist into adulthood or even begin then. Key characteristics include dry, itchy skin and recurring red rashes. These rashes can appear anywhere on the body, with patterns varying by age. Infants commonly develop rashes on the face, scalp, hands, and feet. In children, rashes often occur in the bends of the elbows and knees, as well as on the front of the neck. Adolescents and adults typically experience rashes on the wrists, ankles, and eyelids, in addition to the elbow and knee creases. Scratching can lead to oozing, crusting, and skin thickening (lichenification). The intense itchiness can disrupt sleep and significantly impact quality of life.

The term "atopic" suggests a link to allergies. Although atopic dermatitis isn't always caused by an allergic reaction, it's frequently associated with other allergic conditions. Up to 60% of individuals with atopic dermatitis develop asthma or hay fever (allergic rhinitis) later in life, and up to 30% have food allergies. Atopic dermatitis often marks the start of a progression of allergic disorders known as the "atopic march." This progression typically follows a sequence: atopic dermatitis, then food allergies, hay fever, and finally asthma. However, not everyone with atopic dermatitis will experience the full atopic march, and not all individuals with one allergic disease will develop others.

People with atopic dermatitis have a higher risk of developing other inflammation-related conditions, such as inflammatory bowel disease, rheumatoid arthritis, and alopecia areata (hair loss due to an immune system malfunction). They also face an increased risk of behavioral or psychiatric disorders, like attention-deficit/hyperactivity disorder (ADHD) or depression.

In some individuals with atopic dermatitis, the immune system is compromised and cannot effectively defend against bacteria and fungi (immunodeficiency). These individuals are prone to frequent infections. They often have other allergic conditions such as asthma, hay fever, and food allergies as well.

Atopic dermatitis can also be a symptom of other, distinct disorders that present with a range of signs and symptoms, including skin abnormalities and immunodeficiency. Examples of such disorders include Netherton syndrome, immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome, and severe dermatitis, multiple allergies, metabolic wasting (SAM) syndrome.

Inheritance:

Allergic disorders tend to be hereditary; having a parent with atopic dermatitis, asthma, or hay fever increases the likelihood of developing atopic dermatitis. When caused by mutations in the CARD11 gene, atopic dermatitis follows an autosomal dominant inheritance pattern. This means that having only one copy of the mutated CARD11 gene in each cell is enough to cause the disorder. Similarly, when associated with FLG gene mutations, the condition risk follows an autosomal dominant pattern. A mutation in just one copy of the FLG gene is enough to increase the risk. Individuals with two mutated copies of the FLG gene are more likely to develop the condition and may experience more severe symptoms. When atopic dermatitis is associated with other genetic factors, the inheritance pattern is less clear. While CARD11 gene mutations seem to directly cause the condition, changes in the FLG gene or other genes associated with atopic dermatitis increase a person's risk, but don't guarantee they will develop it. Not everyone with atopic dermatitis has a mutation in a risk-associated gene, and not everyone with a variation in a risk-associated gene will develop the condition.