Definition
Psoriasis is a chronic, immune‑mediated inflammatory disease that most visibly affects the skin, causing sharply demarcated, scaly plaques due to an accelerated turnover of skin cells. It is not contagious and cannot be “caught” through touch, shared water, or sexual contact. The condition results from a complex interplay of genetic susceptibility, immune dysregulation (notably involving IL‑23/Th17 pathways), and environmental triggers. In the United States, psoriasis affects roughly 2–3% of adults.
Features, types, and symptoms
Plaque psoriasis is the most common form, accounting for about 80–90% of cases. Lesions typically appear on the elbows, knees, scalp, and lower back and may itch, burn, or crack. Other clinical variants include guttate, inverse (intertriginous), pustular, and erythrodermic psoriasis; nails and the scalp are frequently involved. Because psoriasis is systemic, symptoms can extend beyond skin, contributing to pain, fatigue, and sleep disturbance.
Causes, triggers, and comorbidities
While the exact cause remains multifactorial, psoriasis often runs in families and reflects an overactive immune response that accelerates keratinocyte proliferation. Common triggers include infections (e.g., streptococcal), skin injury (Koebner phenomenon), stress, and certain medications (such as lithium or beta‑blockers). Importantly, psoriasis is associated with a higher risk of psoriatic arthritis (about one in three people with psoriasis), cardiometabolic disease, and depression, underscoring the need for holistic care.
Diagnosis and severity assessment
Diagnosis is primarily clinical, occasionally supported by skin biopsy when features are atypical. Severity and response to therapy are commonly tracked with standardized measures such as the Psoriasis Area and Severity Index (PASI), which combines lesion redness, thickness, scaling, and body‑surface distribution into a 0–72 score. Modern treatment goals increasingly emphasize near‑complete clearance (PASI 90/100) and meaningful improvements in quality of life.
Treatment and management
Psoriasis management is individualized based on disease extent, sites involved, comorbidities, and patient preference. Options include:
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Topicals (e.g., corticosteroids, vitamin D analogs, retinoids) for limited disease or sensitive areas.
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Phototherapy (narrowband UVB) for more widespread involvement.
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Systemic therapies for moderate‑to‑severe disease, including traditional agents (methotrexate, cyclosporine, acitretin) and targeted treatments. Biologics block specific cytokines (TNF‑α, IL‑17A, IL‑17F, IL‑23, or IL‑12/23). Newer targeted oral therapy includes the TYK2 inhibitor deucravacitinib for adults with moderate‑to‑severe plaque psoriasis. Dual IL‑17A/F inhibition with bimekizumab is also approved for plaque psoriasis. Vaccination planning is important: current expert consensus recommends continuing most systemic therapies for non‑live vaccines, but generally interrupting biologics around live vaccines. Care often benefits from coordination across dermatology, primary care, and (when needed) rheumatology.
Usage areas and importance
“Psoriasis” appears across dermatology, rheumatology (because of psoriatic arthritis), immunology, primary care, behavioral health, and public health. Clinically, it serves as a signal to screen for joint symptoms and cardiovascular risk factors; in research, it is a model disease for targeted immunotherapy and inflammation biology; and in health systems, it guides quality‑of‑life measurement and value‑based care strategies. Given its prevalence, comorbidity burden, and psychosocial impact, timely diagnosis and comprehensive, guideline‑based management can significantly improve outcomes and quality of life.
Sources
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American Academy of Dermatology. Psoriasis: Causes. https://www.aad.org/public/diseases/psoriasis/what/causes
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American Academy of Dermatology. How could I have gotten psoriasis? https://www.aad.org/public/diseases/psoriasis/what/contagious
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American Academy of Dermatology. Psoriasis: Overview. https://www.aad.org/psoriasis-overview
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Medscape. Psoriasis Affects an Estimated 3% of US Adults (NHIS 2023). https://www.medscape.com/viewarticle/psoriasis-affects-estimated-3-us-adults-2024a1000p19
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National Psoriasis Foundation. Get the Facts of Psoriatic Disease (updated Oct 2024). https://www.psoriasis.org/resource-library/get-the-facts-of-psoriatic-disease/
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NIH Research Matters. A cellular and molecular understanding of psoriasis. https://www.nih.gov/news-events/nih-research-matters/cellular-molecular-understanding-psoriasis
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NCBI Bookshelf. Validity of Outcome Measures—PASI (multiple reviews). https://www.ncbi.nlm.nih.gov/books/NBK544841/
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National Psoriasis Foundation and AAD. Guidelines and clinical recommendations. https://www.psoriasis.org/guidelines-treating-your-psoriasis-patients/
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Bristol Myers Squibb. FDA approval announcement for Sotyktu (deucravacitinib). https://news.bms.com/news/corporate-financial/2022/U.S.-Food-and-Drug-Administration-Approves-Sotyktu-deucravacitinib-Oral-Treatment-for-Adults-with-Moderate-to-Severe-Plaque-Psoriasis/default.aspx
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UCB. FDA approvals for BIMZELX (bimekizumab). https://www.ucb-usa.com/stories-media/UCB-U-S-News/detail/article/ucb-announces-us-fda-approvals-for-bimzelxr-bimekizumab-bkzx-for-the-treatment-of-psoriatic-arthritis-non-radiographic-axial-spondyloarthritis-and-ankylosing-spondylitis
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PubMed. Vaccination recommendations for adults receiving biologics and oral therapies for psoriasis (2024). https://pubmed.ncbi.nlm.nih.gov/38331098/
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