Psoriasis

Psoriasis is an inflammatory dermatological disease with several variants. The most common variant is plaque psoriasis, other variants of the disease are guttate, erythrodermic and pustular psoriasis ¹.

Epidemiology

There is a geographic variation in the prevalence of psoriasis such that populations further away from the equator have a higher disease burden. The disease is particularly prevalent in Norway where 8% of adults suffer from it ². In all populations, children are less affected than adults ². In most populations, psoriasis appears to affect men and women equally; about a quarter of psoriasis patients have been diagnosed with psoriatic arthritis. Careful radiological imaging studies indicate the prevalence of arthritis in these patients may be even higher ³.

Associations

• psoriatic arthritis

• depression and psychiatric disorders

• inflammatory bowel disease

• cardiometabolic disease

Clinical presentation

More than one variant of psoriasis may co-exist in a single patient. All variants involve skin changes, consisting usually scaling and erythema.

• plaque psoriasis: manifests predominantly in scaly, relatively larger, patches of skin

• pustular psoriasis: a rare form of psoriasis with pustules

• guttate psoriasis: small erythematous lesions (<2 cm) which may coalesce

• erythrodermic psoriasis: a severe and potentially fatal variant of psoriasis in which most of the skin is affected

Additionally, psoriasis may have pulmonary manifestations, but these are rare.

Diagnosis

The diagnosis of psoriasis is clinical. Biopsy and pathology work-up are not necessary in the vast majority of cases. The possible comorbidity of psoriatic arthritis should be considered, and manifestations of the disease on the nails may be a predictor of this possibility ⁴.

Pathology

Psoriasis is a chronic inflammatory autoimmune disease in which genetic background and environmental triggers both play a role ^1,5. Overactivation of the adaptive immune system affects keratinocytes.

Treatment and prognosis

The treatment of most psoriasis cases will involve topical agents including steroids, vitamin D analogs, calcineurin inhibitors and keratolytics ¹. Phototherapy, in which patients are exposed to ultraviolet light, also improves the disease. In more severe cases, biologics such as TNF-alpha inhibitors are used.

Differential diagnosis

Differential considerations include:

• pityriasis rosea

• atopic dermatitis

• nummular dermatitis ⁵

• cutaneous T-cell lymphoma

• syphilis ¹