Psoriasis

Psoriasis is a chronic immune-mediated disease of the skin. The prevalence of psoriasis is 2%-4% in the United States and worldwide. Psoriasis is strongly associated with psoriatic arthritis, obesity, hypertension, diabetes, and cardiovascular disease. Tailored management has been shown to affect long-term cardiovascular morbidity. Recent advances in psoriasis immunobiology have led to an increase in new immunologic and targeted small-molecule therapies with impressive patient outcomes. Notably, the elucidated interleukin-17 (IL-17) and type 17 helper T-cell (Th17) lineage appear to be critical to the immunopathology of psoriasis.

Pathophysiology

See this interactive graphic for an overview of the basic steps leading to plaque psoriasis.

The following table describes functionality of interleukin-17 in human disease:

(Source: Interleukin-17 and Type 17 Helper T Cells. N Engl J Med 2009.)

Triggering Factors

In genetically predisposed persons (e.g., HLA-Cw6-positive), external triggers (e.g., skin trauma or systemic trauma such as streptococcal pharyngitis) can elicit psoriasis.

Psoriasis triggers include the following:

• external trauma (Koebner phenomenon)

• infections (streptococcal, HIV)

• psychogenic stress

• medication (antimalarials, lithium, interferon, nonsteroidal anti-inflammatory drugs, beta-blockers)

• rapid taper of systemic glucocorticoids (e.g., in the setting of treating severe poison ivy eruption)

• alcohol intake and cigarette smoking

Clinical Manifestations

Chronic plaque psoriasis, the most common manifestation, is characterized by well-demarcated oval plaques of varying sizes that have a pink-red base covered with a dry silver-white scale. The most common sites of involvement include the scalp, extensor surfaces of the limbs, gluteal cleft, and umbilicus. Nails are also frequently affected and can display pitting, dystrophy, and discoloration. The distribution is almost always symmetric. Psoriasis is one of several cutaneous diseases that can present in areas of prior trauma, described as Koebner phenomenon (see examples below of the aforementioned cutaneous findings).

Other subtypes of psoriasis:

• inverse (i.e., affecting flexural as opposed to extensor surfaces)

• infantile (also referred to as napkin psoriasis)

• guttate (frequently associated with streptococcal infection)

• generalized pustular

• impetigo herpetiformis (pustular psoriasis during pregnancy)

• acrodermatitis continua of Hallopeau (pustular variant that affects distal digits)

Images of Psoriasis

(Source: VisualDx 2023.)

(Source: Psoriasis. N Engl J Med 2009.)

(Source: Psoriasis. N Engl J Med 2009.)

(Source: Generalized Ostraceous Psoriasis. N Engl J Med 2010.)

(Source: Psoriasis. N Engl J Med 2005.)

(Source: NEJM Knowledge Plus. Massachusetts Medical Society 2021.)

(Source: Psoriasis. N Engl J Med 2005.)

(Source: Psoriasis Flare from Koebner’s Phenomenon after Acupuncture. N Engl J Med 2013.)

(Source: VisualDx 2023.)

(Source: Psoriasis. N Engl J Med 2005.)

(Source: Psoriasis. N Engl J Med 2005.)

(Source: Psoriasis. N Engl J Med 2009.)

Management

The management of psoriasis includes a stepwise approach that takes into consideration the severity of disease, as well as the severity of symptoms associated with an individual’s disease. Additionally, it is critical to evaluate the patient initially for psoriatic arthritis, as the presence of psoriatic arthritis will also alter the treatment algorithm to favor the use of biologics. First-line treatment for psoriatic arthritis or axial skeletal involvement is systemic biologic therapy.

Topical medications for psoriasis include vitamin D₃ analogues, calcineurin inhibitors, topical retinoids, phosphodiesterase type 4 inhibitors, aryl hydrocarbon-receptor agonists, and glucocorticoids. Systemic therapy and ultraviolet light can be used in moderate-to-severe disease. A variety of biologics are now available that target different parts of the immune system (full details are available here). In addition, selective oral treatments (e.g., phosphodiesterase type 4 inhibitors, Janus kinase inhibitors, and tyrosine kinase 2 inhibitors) have also become available.

Psoriasis and Cardiovascular Disease (CVD)

Research has consistently shown strong associations between psoriasis and CVD. The association is primarily in patients with more-severe psoriasis involving more than 10% body surface area (BSA), and usually these are the patients that require systemic therapy. It is important to recommend both lifestyle modifications and standard preventative therapies to reduce CVD-disease risk. For a forest plot of the associations between psoriasis and CVD mortality, myocardial infarction (MI), and stroke, see this systematic review and meta-analysis.