Elsevier

The Lancet

Volume 397, Issue 10281, 3–9 April 2021, Pages 1301-1315
The Lancet

Seminar
Psoriasis

https://doi.org/10.1016/S0140-6736(20)32549-6Get rights and content

Summary

Psoriasis is a common, chronic papulosquamous skin disease occurring worldwide, presenting at any age, and leading to a substantial burden for individuals and society. It is associated with several important medical conditions, including depression, psoriatic arthritis, and cardiometabolic syndrome. Its most common form, chronic plaque or psoriasis vulgaris, is a consequence of genetic susceptibility, particularly in the presence of the HLA-C*06:02 risk allele, and of environmental triggers such as streptococcal infection, stress, smoking, obesity, and alcohol consumption. There are several phenotypes and research has separated pustular from chronic plaque forms. Immunological and genetic studies have identified IL-17 and IL-23 as key drivers of psoriasis pathogenesis. Immune targeting of these cytokines and of TNFα by biological therapies has revolutionised the care of severe chronic plaque disease. Psoriasis cannot currently be cured, but management should aim to minimise physical and psychological harm by treating patients early in the disease process, identifying and preventing associated multimorbidity, instilling lifestyle modifications, and employing a personalised approach to treatment.

Section snippets

Epidemiology and disease burden

Psoriasis is an inflammatory skin disease that is associated with many other medical conditions, and affects over 60 million adults and children worldwide.1 Establishing the global burden of psoriasis is a key research imperative of WHO. In 2014, the organisation passed a resolution recognising psoriasis as a “chronic, non-communicable, painful, disfiguring, and disabling disease for which there is no cure”.1 Psoriasis occurs equally in men and women, with a mean age of onset of 33 years. It

Chronic plaque

Psoriasis has different clinical phenotypes, but the most frequent and most easily recognised is chronic plaque or psoriasis vulgaris. The classic morphology is that of well demarcated, salmon-pink plaques covered in silvery scales in white skin (figure 1A) and of grey plaques in black skin (figure 1B). Removal of the adherent scales can result in small bleeding points (known as the Auspitz sign). Plaques can have highly variable sizes and thicknesses, which can in turn signify active disease

Diagnostic investigation and differential diagnoses

The diagnosis of psoriasis is usually clinical, on the basis of the history, morphology, and distribution of skin lesions. Obtaining the patient's history should help to establish if there is a family history of psoriasis, potential triggers, the onset of psoriasis symptoms, and whether there are musculoskeletal symptoms suggestive of psoriatic arthritis. A thorough skin examination needs to include inspection of the nails, scalp, flexures, and intergluteal cleft. Because patients are often

Histological features

The histology of psoriasis includes thickening of the epidermis (acanthosis) with downward elongation of rete ridges, a thinned or absent granular layer, elongated and dilated capillaries, suprapapillary thinning, an inflammatory infiltrate of T cells in the dermis and epidermis, and sometimes clusters of neutrophils in the parakeratotic scale. When present, neutrophil clustering in pustules (Kogoj spongiform micropustules), or surrounded by parakeratosis (microabscesses of Munro), can be

Overall treatment strategy for plaque psoriasis

In general, treatment strategies for plaque psoriasis should account for psoriasis severity, presence of psoriatic arthritis, consideration of other associated medical conditions, and patient preference and satisfaction. For example, if a patient has psoriatic arthritis, the treatment regimen should, if possible, include a systemic medication that treats this condition in addition to psoriasis. Psoriasis severity, location, and multimorbidity contribute to the choice of treatment.95, 96

SARS-CoV-2 and psoriasis

The COVID-19 pandemic has created substantial challenges to the management of psoriasis. Although there is currently no direct evidence that psoriasis is itself a risk factor for COVID-19 infection or worse disease outcomes, theoretically, people with severe disease could potentially be at higher risk, given that they have comorbidities such as obesity and diabetes. Furthermore, there is some evidence that people with immune-mediated inflammatory diseases are at greater risk than is the general

Unresolved questions, new developments, and unmet medical needs

Translational medicine has epitomised psoriasis research for the past 25 years, transforming the lives of many patients in the process, but unanswered questions remain. The contribution of genetics to disease expression is undoubted, yet the mechanisms underlying environmental triggers are elusive. The role of the microbiome might be a key player in this interaction between genetic susceptibility and environmental triggers, as are the contributions of stress and infection; the COVID-19 pandemic

Conclusion

The intricacies of psoriasis are slowly being uncovered. There is widespread agreement that psoriasis is genetically predetermined, its expression partly determined by immune factors and environmental exposures, and that it will eventually be reclassified into several taxonomically distinct endotypes. Consensus is also emerging that it has various systemic consequences. This realisation mandates a holistic and proactive approach to psoriasis care, factoring in lifestyle management,

Search strategy and selection criteria

We searched PubMed, MEDLINE, and Cochrane Library with the search term “psoriasis” in combination with terms “epidemiology”, “phenotypes”, “genetics”, “pathogenesis”, “comorbidities”, “therapy”, “management”, “recommendations”, and “guidelines”. We focused on all relevant publications publications in English from the past 10 years (May 14, 2010, to May 14, 2020), but did not exclude commonly referenced older publications. We identified additional reports from the references in systematic

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