What is plaque psoriasis?

Plaque psoriasis is the most common presentation of psoriasis, with up to 80-90% of people with psoriasis having this type.¹ Plaque psoriasis is defined by the presence of raised and inflamed areas of skin with silvery scales. They can be itchy or painful, and most commonly appear on the elbows, knees, torso, or scalp, but can appear anywhere on the body. Sometimes, patients can concurrently have a second kind of psoriasis in addition to plaque psoriasis. Some other types include guttate, pustular, inverse, or erythrodermic. The inflammatory process causing plaque psoriasis is likely from the migration of immune cells into the skin.² Common triggers of plaque psoriasis include certain medications, abruptly starting or stopping medications, infections, injury to the skin, stress, and tobacco or alcohol use.³

Symptoms

Plaque psoriasis is characterized by dry, well-defined, and irregularly shaped skin lesions that can be painful or itchy. There are often also silvery scales overlying the swollen patches of skin. Psoriasis lesions tend to be distributed bilaterally, meaning they will appear on both sides of the body and are usually red or pink in colour. Each individual lesion can vary from one to several centimeters. Typical places for lesions include the extensor surfaces, such as elbows and knees. Plaque psoriasis can also involve the nails, leaving small but visible pits on each one.⁴

Diagnosis

Plaque psoriasis is clinically diagnosed, meaning that your doctor will take a thorough history and do a full physical examination, including taking a close look at your skin. They may ask you questions about when or how you first noticed your lesions, what symptoms you have, and what parts of your body are affected.⁵ A skin biopsy, where a small sample of the affected skin is sent to the pathologist to view under a microscope, may sometimes be performed to confirm diagnosis but is often unnecessary.⁶

Treatment

While psoriasis cannot be cured, there are many effective treatment options, both topical and systemic, to manage symptoms. The mainstay of treatment for patients with mild-to-moderate plaque psoriasis is topical treatments including: corticosteroids, vitamin D analogs or retinoids. Topical steroids work through their anti-inflammatory and immunosuppressive properties but should be used with caution on the face and in skin folds to prevent unnecessary skin thinning. In moderate-to-severe psoriasis, phototherapy is often chosen as a first-line treatment. If phototherapy is not available where you are, systemic oral treatments, such as methotrexate or acitretin or novel small molecules such as apremilast can also be used. Biologics have emerged as a highly potent and effective systemic option for patients in whom other therapies have not worked.⁵

References

1. Wilson FC, Icen M, Crowson CS, McEvoy MT, Gabriel SE, Kremers HM. Incidence and clinical predictors of psoriatic arthritis in patients with psoriasis: A population-based study. Arthritis & Rheumatism. 2009;61(2):233-239.
2. Hsu S, Papp KA, Lebwohl MG, et al. Consensus guidelines for the management of plaque psoriasis. Arch Dermatol. 2012;148(1):95-102.
3. Lee EB, Wu KK, Lee MP, Bhutani T, Wu JJ. Psoriasis risk factors and triggers. Cutis. 2018;102(5S):18-20.
4. Parisi R, Iskandar IYK, Kontopantelis E, et al. National, regional, and worldwide epidemiology of psoriasis: systematic analysis and modelling study. BMJ. 2020;369:m1590.
5. Kim WB, Jerome D, Yeung J. Diagnosis and management of psoriasis. Can Fam Physician. 2017;63(4):278-285.
6. Johnson MAN, Armstrong AW. Clinical and histologic diagnostic guidelines for psoriasis: a critical review. Clin Rev Allergy Immunol. 2013;44(2):166-172.