Often confused with atopic dermatitis, psoriasis is also an incurable chronic skin condition that is characterized by itchy/inflamed and scaly patches of skin. As psoriasis affects ~2% of the United States population, the demand for treatment continues to soar. Unfortunately, psoriasis is a complex autoimmune condition that entails various factors. In this post, we’ll learn about the causes of psoriasis, the role of the immune system in psoriasis, remedies, as well as how it differs from other inflammatory skin conditions like eczema.
What causes psoriasis?
The root causes of psoriasis start with genetics and environmental triggers. This combination is integral for psoriasis, with genetic predispositions endangering the host to an overreactive immune response, which can be provoked by an environmental trigger. Triggers include skin injuries, infections, stress, alcohol, and more.
What happens during a psoriasis flare-up?
Once triggered, the immune system begins to malfunction. Crucial immune cells known as t cells—responsible for fighting off pathogens—become overactive. They begin to mistakenly orchestrate an attack on skin cells, assuming them to be pathogens. First, T cells release cytokines (typically IL-17 and IL-23)—proteins that regulate immune responses and contribute to inflammation. These cytokines then stimulate the overproduction of keratinocytes (skin cells) to try to repair the damage. The basal layer of the epidermis (where keratinocytes are produced) then goes overdrive, resulting in rapid cell division. This manifests as flaky, inflamed, and itchy lesions of the skin of psoriasis.
Here is a flowchart to help demonstrate the process:
Genetic predisposition and environmental triggers
T cells become overactive
T cells release cytokines
Cytokines stimulate keratinocyte overproduction
Visible symptoms of psoriasis (Scaly, itchy plaques)
Psoriasis vs. atopic dermatitis
Psoriasis and atopic dermatitis are both chronic skin conditions that manifest as flaky, inflamed, and itchy patches of skin. However, the difference between these two comes down to their underlying cause. As we’ve learned, psoriasis is an autoimmune condition that involves the immune system mistakenly attacking the body. In contrast, atopic dermatitis is an inflammatory condition involving a defective/hypersensitive skin barrier due to genetic mutation. Although psoriasis can also be triggered by environmental triggers, think of atopic dermatitis as being the direct, inflammatory response to a trigger. Psoriasis, on the other hand, happens because the immune system is already defective and attacking the body’s own skin cells, and outside triggers just make it worse.
Types of psoriasis
Psoriasis can take on several forms, depending on the types of cytokines involved. Accounting for 80-90% of psoriasis cases, plaque psoriasis is the most common form. Primary cytokines involved: IL-17 and IL-23. Manifests as raised, silver-colored, scaly patches of skin. Most commonly forms on the elbows and knees. Psoriasis can also take several other forms, affecting different parts of the body. These include: guttate psoriasis (torso, upper arms, and legs), pustular psoriasis (palms of hands or soles of feet), inverse psoriasis (skin folds), and many more.
Treatments:
Luckily, scientists have developed various treatment options for psoriasis that work by reducing inflammation and slowing the overproduction of skin cells. Treatments include topical therapies (creams and ointments), light therapy, and oral or injected medications. The best option for each patient depends on the severity of the condition, medical history, and lifestyle.
Conclusion:
Understanding the biochemistry and immunology behind psoriasis reveals the complexity of this abstract, chronic, autoimmune condition. Although there isn’t currently a direct cure for psoriasis, several treatments have been developed to mitigate symptoms, reduce inflammation, and prevent flare-ups. The more we understand the underlying cause of psoriasis, the closer we get to hopefully curing this chronic condition.
Bibliography
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