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Psoriasis is a chronic inflammatory skin condition that affects up to 2% of the world’s population. Psoriasis can not only increase morbidity and mortality in patients but also impacts the quality of life. People with psoriasis have a higher risk of heart disease and metabolic syndrome.

What is psoriasis?

Psoriasis is a skin disease caused by abnormalities in the patient’s adaptive and innate immunity. The most recognised cytokines that are aberrant in psoriasis include IFN, NF-kB, IL23, and IL17. The result of abnormal signalling is increased T cell activation, increased dendritic cells, and proliferation of keratinocytes causing the plaques we can see.

Recognising psoriasis

There are several variants of psoriasis, but by far the most common is the plaque type. Plaque psoriasis involves ovoid, well-demarcated pink scaly plaques that favour areas of friction such as the elbows and knees. Flares are often accompanied by various triggers, which include strep throat or other bacterial infections, medications, stress, smoking, HIV, obesity, and alcohol use. Usually, psoriasis presents at age 20-30 or 50-60, though it can appear at any age. Many patients will have a positive family history.

Diagnosis

Psoriasis can be diagnosed clinically, though a biopsy is very helpful if the diagnosis is in question. Punch biopsy is the favoured technique, with histology showing neutrophils in the stratum corneum, regular acanthosis, and vascular ectasias between rete ridges. Other diseases that may look like psoriasis include atopic dermatitis, tinea corporis, pityriasis rosea, pityriasis rubra pilaris, and other papulosquamous disorders. Psoriasis that does not get better with treatment should always be biopsied to confirm the diagnosis and rule out cutaneous malignancies or infections.

Treatment

Treatment is based on the severity of psoriasis. A good estimate for severity is with the body surface area estimation. The easiest way to estimate body surface area is the equate 1% to the surface are of the patient’s own palm. As a general rule of thumb, mild psoriasis is less than 3%, moderate 3-10%, and severe is over 10%.

Besides body surface area, joint involvement is also important to consider when managing psoriasis. It is incredibly important to involve the rheumatologist to help differentiate inflammatory versus osteoarthritis in patients who have psoriasis.

Treatment for mild psoriasis

First-line treatment for mild psoriasis is with topical steroids. A medium potency steroid is a good place to start for plaques on the body, and a higher potency may be needed if plaques are thicker or recalcitrant. To avoid the side effects of topical steroids, patients should not use potent steroids for more than two weeks in a row.

Other topicals that may be helpful for psoriasis include topical vitamin D formulations and retinoids. Treatment-resistant psoriasis may need systemic therapies. If joint pain is present, the patient will need to be evaluated by a rheumatologist for psoriatic arthritis.

Systemic steroids are almost never used for psoriasis. Systemic steroids can put patients at risk of a life-threatening flare once tapered. Better options include apremilast, methotrexate, and cyclosporine for limited periods of time. Biologics have been a huge game-changer for the treatment of psoriasis. These medications are very effective and safe but may be challenging to prescribe in resource limited areas.

Learn more in the Professional Diploma program in General Dermatology.

Sources

Peter C.M. van de Kerkhof and Frank O. Nestle. Psoriasis. In: Dermatology. 4th ed. Philadelphia, PA: Elsevier Saunders; 2012:138-159

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