Psoriasis in Adult
Psoriasis is a polygenic disease. (Several psoriasis susceptibility genes have been identified over recent years.) Certain individuals with genetic susceptibility develop a psoriatic phenotype after exposure to environmental triggers such as infection, medications, and medical comorbidities, among others. Aberrant T-cell function and keratinocyte responses are believed to be major culprits in the pathogenesis of psoriasis.
There are several variants of the disease, and variants can coexist in the same individual.
Chronic plaque psoriasis is most common, and disease burden can range from 1%-2% (mild disease) to greater than 90% (erythrodermic psoriasis) of the total body surface area (BSA). Typical findings include well-demarcated circular, oval, or polycyclic erythematous plaques with micaceous scale that are often symmetric in distribution. The scalp, elbows, and knees are commonly involved. Lesions are often pruritic and resolve with postinflammatory hyper- or hypopigmentation. Scarring is not a feature of resolution. During exacerbations, erythematous papules usually surround existing plaques, and a ring of intense erythema surrounds the plaques. During resolution, plaques will often have a decreased amount of scale and central clearing, creating annular psoriatic lesions. Lesions can last from months to years in the same location.
Inverse psoriasis occurs in intertriginous areas of the body, such as the axillae, groin, genitals, and submammary area.
When psoriasis involves areas of the face other than the hairline, eyebrows, and beard, it is usually an indication of more severe disease. Seborrheic dermatitis can coexist with psoriasis on the face and scalp (sometimes referred to as "sebopsoriasis").
Other variants include:
- Psoriatic arthritis – Up to 50% of psoriatic individuals may have erosive psoriatic arthritis. Psoriatic arthritis is more common among individuals with nail and scalp psoriasis. Rarely, psoriatic arthritis has been reported to develop prior to the cutaneous findings of psoriasis.
- Guttate psoriasis – An acute generalized eruption of small, discrete, raindrop-like papules with fine scale. This may occur 2-3 weeks after an upper respiratory infection and is most common in children.
- Erythrodermic psoriasis – An uncommon but potentially life-threatening acute complication of psoriasis wherein large red patches with desquamation cover most of the body surface.
- Pustular psoriasis – An uncommon, sometimes severe, variant characterized by widespread erythematous, sterile pustules.
- Acrodermatitis continua of Hallopeau – An uncommon variant of pustular psoriasis affecting the hands and feet.
- Inverse psoriasis – Psoriasis that involves the intertriginous areas including the axillae, inframammary areas, and inguinal folds. The plaques of inverse psoriasis are erythematous and well-demarcated but often lack the classic scale as these body sites are generally moist.
- Nail psoriasis – The nails of individuals with psoriasis can show several features. The most common are pitting, distal onycholysis, and splinter hemorrhages. Individuals with nail psoriasis are at an increased risk of developing psoriatic arthritis.
- Approximately 50% of women report improvement of disease burden during pregnancy.
- Pustular psoriasis developing in hypocalcemic women during pregnancy is known as impetigo herpetiformis.
- HIV infection may precipitate or exacerbate psoriasis.
L40.0 – Psoriasis vulgaris
9014002 – Psoriasis
- Chronic atopic dermatitis – Atopic history, commonly starts in childhood. Mild-to-moderate spongiosis seen on histology. Lichenified plaques on the flexural surfaces and neck. More pruritic than psoriasis.
- Contact dermatitis (allergic, irritant)
- Nummular dermatitis – Intensely pruritic coin-shaped lesions, almost exclusively on the extremities.
- Lichen simplex chronicus – Common around the ankles.
- Seborrheic dermatitis – Sebaceous distribution.
- Lichen planus – Very pruritic, often associated with hepatitis C. Biopsy will differentiate psoriasis from lichen planus.
- Tinea corporis – Scale at leading edge of erythema with central clearing. Check potassium hydroxide (KOH) preparation.
- Drug eruption – Drug eruptions often present with urticarial, exanthematous, or vesicular / bullous lesions. In addition, systemic symptoms are more pronounced than seen with classic psoriasis, including fever, lymphadenopathy, and facial edema. Eosinophilia on CBC and histology are often seen (but not an invariable finding). NSAIDs, sulfonamides, and penicillin are frequently implicated.
- Subacute cutaneous lupus erythematosus (SCLE) – Antinuclear antibody (ANA) will be positive in most lupus patients. SCLE is characterized by annular plaques with raised borders and central clearing or papulosquamous lesions that are restricted to sun-exposed skin.
- Pityriasis lichenoides chronica – Usually smaller papules. Biopsy will assist in differentiating from psoriasis, predominantly CD8+ T-cell infiltrate.
- Lymphomatoid papulosis – Crusted papules and smaller papules. Biopsy will assist in differentiating from psoriasis, predominantly CD30+ T-cell infiltrate.
- Pityriasis rubra pilaris (PRP) – Orange-red, wax-like keratoderma of the palms and soles. Islands of normal skin within larger plaques are characteristically seen in PRP. PRP and psoriasis are histologically different, and a biopsy will aid in the diagnosis. Family history of psoriasis is common in psoriatic patients.
- Mycosis fungoides – Early mycosis fungoides is often misdiagnosed as psoriasis. With time, generalized lymphadenopathy, circulating malignant lymphocytes, leonine facies, and a CD4/CD8 ratio greater than 10.
- Secondary syphilis – Rapid plasma reagin (RPR) test, history of primary chancre, and systemic symptoms.
- Erythema annulare centrifugum
- Extramammary Paget disease
- Pityriasis rosea – Herald patch, collarette of scale, and orientation of lesions ("fir tree" pattern in skin tension lines). Does not follow an intermittently relapsing course.
- Crusted scabies – Most common in elderly, immunocompromised, or institutionalized patients.
- Reactive arthritis (Reiter syndrome)
- Acrokeratosis paraneoplastica (Bazex syndrome)
- Caspase recruitment domain family member 14 gene (CARD14)-associated papulosquamous eruption refers to a distinctive phenotype with overlapping features of psoriasis and PRP. Patients typically present early in life and report a family history of psoriasis or PRP. The cheeks, chin, and ears are typically affected. This disease is difficult to treat using conventional therapies, while treatment with ustekinumab appears to be effective.