Psoriasis

Last updated: October 6, 2022

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Psoriasis is a common chronic inflammatory skin disorder affecting individuals with an underlying genetic predisposition. Triggering events (e.g., infection, medication) can lead to disease manifestation. Psoriasis typically manifests as sharply demarcated, erythematous, scaly, pruritic plaques, most commonly occurring on the scalp, presacral region, and extensor surfaces of the knees and elbows; however, any area of the skin may be affected. Other common clinical findings include arthritis, generally affecting the fingers and lower spine, and nail involvement (e.g., pitting, discoloration). The size, location, and severity of psoriasis lesions vary depending on the subtype. The diagnosis is primarily clinical, based on the patient's symptoms, history, and the presence of any specific signs (e.g., the Auspitz sign); a biopsy is rarely indicated. Mild psoriasis can be treated with topical agents such as corticosteroids, whereas moderate to severe disease requires systemic therapy (e.g., phototherapy, biologic agents).

  • Prevalence: ∼ 2% of the US population [1][2][3]
  • Age of onset: : can present at any age; typically shows bimodal age distribution [1][4]
    • Early onset psoriasis: (∼ 75% of cases): before 40 years of age
    • Late onset psoriasis (∼ 25% of cases): after 40 years of age; usually mild

Epidemiological data refers to the US, unless otherwise specified.

The mechanism causing the immune response is not yet well understood.

References:[7]

The disease course is typically relapsing, with symptom-free intervals.

Cutaneous lesions [2]

  • Well-demarcated, erythematous plaques and/or papules with silver-white scaling
  • Typically, a few single lesions initially appear, often becoming confluent. [2]
  • Located mainly on the scalp, trunk, elbows, and knees (extensor surfaces), but any area of the skin may be affected.
  • Pruritus in ∼ 80% of cases (typically mild, but may be severe in some cases) [8]
  • Characteristic features may be present.
    • Auspitz sign ; [2]
      • Small pinpoint bleeding when scales are scraped off
      • Removal of the scales exposes the dermal papillae, which leads to bleeding.
    • Koebner phenomenon: Physical stimuli or skin injury (e.g., trauma, scratching, irritating clothing) can lead to the appearance of psoriatic skin lesions on previously unaffected skin (isomorphic response). [2]

Cutaneous variants [2]

Plaque psoriasis is the most common psoriasis variant (accounts for ∼ 80–90% of psoriasis cases). [2]

Erythrodermic and generalized pustular psoriasis can lead to severe, life-threatening illness, which must be treated as a medical emergency. [2]

Nail involvement [2]

Present in ∼ 50% of cases [9]

Clinical features vary depending on the cutaneous variant. Erythema, thickening, and scaling are present in most variants. [2]

Definition

Psoriatic arthritis (PsA) is a type of inflammatory arthritis that primarily affects the hands, feet, and/or spine and occurs in up to 30% of patients with psoriasis. [10]

Psoriasis and PsA can occur together or alone

Clinical features [10][11]

Arthritis [10][11]

Multiple patterns may be present.

Accompanying features [10]

In PsA, patterns of joint involvement can change over time and vary widely between patients. Oligoarthritis tends to be more common at onset, while polyarthritis may develop in later stages. [10]

Diagnostics [10][11]

General principles

  • Diagnosis is mainly clinical, based on patient and family history and clinical features.
  • lmaging studies can support the diagnosis and help estimate severity.
  • Laboratory studies are usually obtained as a part of the inflammatory arthritis workup.
  • Consult rheumatology for all patients.

Imaging studies [10][11]

Laboratory studies [10]

Laboratory studies may be obtained to rule out other diagnoses but are not typically required to make a diagnosis of PsA.

Rheumatoid factor is typically negative in patients with PsA, which can help rule out differential diagnoses of inflammatory arthritis. [10]

Classification criteria

These classification criteria are not diagnostic but can provide guidance in clinical practice. [10]

Classification criteria for psoriatic arthritis (CASPAR) [10][12]
Criteria Score
Clinical features
  • Current psoriasis
2
1
1
1
Diagnostic studies 1
  • Radiologic signs of PsA
1

Interpretation

A total score of ≥ 3 points indicates PsA.

Treatment [11][13]

General principles

  • Treatment depends on disease severity and the presence of certain features and/or comorbidities.
  • A treat-to-target approach with a target of remission or low disease activity is recommended. [13]
  • Consult a rheumatologist before starting pharmacotherapy.

Pharmacological treatment [11][13]

Systemic glucocorticoids are not commonly used in PsA because of concerns that tapering too rapidly may induce a flare of cutaneous disease. [11]

Supportive management [13]

Psoriasis is a clinical diagnosis based on patient and family history and thorough skin examination.

Approach [2][14]

All patients with psoriasis should be evaluated for psoriatic arthritis, as early diagnosis improves outcomes and the presence of psoriatic arthritis influences treatment decisions. [2]

Skin biopsy [15]

Differential diagnosis of scaling
Disorder Lesion Distribution
Psoriasis
Atopic dermatitis
  • Extensor surfaces of extremities (e.g., shins)
  • Flexural creases (antecubital, popliteal)
Seborrheic dermatitis
Pityriasis rubra pilaris
  • Typically palms and soles
  • Islands of unaffected skin (sparing)
  • Follicular keratosis
Erythroderma [16]

The differential diagnoses listed here are not exhaustive.

The following recommendations apply to the treatment of plaque psoriasis ; consult a specialist before initiating treatment.

Approach [2][14][17]

Treatment depends on disease severity, comorbidities, and patient preference.

All patients with plaque psoriasis and concomitant psoriatic arthritis require systemic treatment. [2]

Topical pharmacotherapy [2][17]

Topical pharmacotherapy is the mainstay of mild psoriasis treatment.

Commonly used combinations include topical corticosteroids plus either vitamin D analogues or keratolytic agents. Combination therapy increases efficacy and may cause fewer adverse effects than monotherapy.

Systemic pharmacotherapy [18][19]

Supportive care [17]

Alcohol consumption and tobacco use are associated with increased disease severity and ASCVD risk. [14]

Increased risk of other comorbidities:

We list the most important complications. The selection is not exhaustive.

  • Lifelong disease, usually benign
  • Patients may experience remissions of varying lengths; acute episodes of exacerbation possible.
  • Psoriasis is associated with depression and a decreased quality of life.
  1. Langley RGB. Psoriasis: epidemiology, clinical features, and quality of life. Ann Rheum Dis. 2005; 64 (suppl_2): p.ii18-ii23. doi: 10.1136/ard.2004.033217 . | Open in Read by QxMD
  2. Armstrong AW, Read C. Pathophysiology, Clinical Presentation, and Treatment of Psoriasis. JAMA. 2020; 323 (19): p.1945. doi: 10.1001/jama.2020.4006 . | Open in Read by QxMD
  3. Parisi R, Symmons DP, Griffiths CE, Ashcroft DM. Global epidemiology of psoriasis: a systematic review of incidence and prevalence. J Invest Dermatol. 2013; 133 (2): p.377-385. doi: 10.1038/jid.2012.339 . | Open in Read by QxMD
  4. Queiro R, Tejón P, Alonso S, Coto P. Age at disease onset: a key factor for understanding psoriatic disease. Rheumatology. 2013; 53 (7): p.1178-1185. doi: 10.1093/rheumatology/ket363 . | Open in Read by QxMD
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  6. Feldman SR. Epidemiology, Clinical Manifestations, and Diagnosis of Psoriasis. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/epidemiology-clinical-manifestations-and-diagnosis-of-psoriasis.Last updated: December 9, 2015. Accessed: May 16, 2017.
  7. Lowes MA, Suárez-Fariñas M, Krueger JG. Immunology of psoriasis. Annu Rev Immunol. 2014; 32 : p.227-255. doi: 10.1146/annurev-immunol-032713-120225 . | Open in Read by QxMD
  8. Pruritus severity in patients with psoriasis is not correlated with psoriasis disease severity. http://www.jaad.org/article/S0190-9622(13)01012-8/abstract. Updated: February 1, 2014. Accessed: May 16, 2017.
  9. Rosso Schons KR, Faccin Knob C, Murussi N, Costa Beber AA, Neumaier W, Monticielo OA. Nail psoriasis: a review of the literature. An Bras Dermatol. 2014; 89 (2): p.312-317. doi: 10.1590/abd1806-4841.20142633 . | Open in Read by QxMD
  10. Elmets CA, Leonardi CL, Davis DMR, et al. Joint AAD-NPF guidelines of care for the management and treatment of psoriasis with awareness and attention to comorbidities. J Am Acad Dermatol. 2019; 80 (4): p.1073-1113. doi: 10.1016/j.jaad.2018.11.058 . | Open in Read by QxMD
  11. Jacobi A, Prinz JC. Autoimmune Diseases of the Skin. Springer Science & Business Media ; 2005 : p. 327
  12. Davis MDP. Erythroderma in Adults. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/erythroderma-in-adults.Last updated: September 21, 2016. Accessed: September 2, 2017.
  13. Elmets CA, Korman NJ, Prater EF, et al. Joint AAD–NPF Guidelines of care for the management and treatment of psoriasis with topical therapy and alternative medicine modalities for psoriasis severity measures. J Am Acad Dermatol. 2021; 84 (2): p.432-470. doi: 10.1016/j.jaad.2020.07.087 . | Open in Read by QxMD
  14. Menter A, Strober BE, Kaplan DH, et al. Joint AAD-NPF guidelines of care for the management and treatment of psoriasis with biologics. J Am Acad Dermatol. 2019; 80 (4): p.1029-1072. doi: 10.1016/j.jaad.2018.11.057 . | Open in Read by QxMD
  15. Menter A, Gelfand JM, Connor C, et al. Joint American Academy of Dermatology–National Psoriasis Foundation guidelines of care for the management of psoriasis with systemic nonbiologic therapies. J Am Acad Dermatol. 2020; 82 (6): p.1445-1486. doi: 10.1016/j.jaad.2020.02.044 . | Open in Read by QxMD
  16. Ritchlin CT, Colbert RA, Gladman DD. Psoriatic Arthritis. N Engl J Med. 2017; 376 (10): p.957-970. doi: 10.1056/nejmra1505557 . | Open in Read by QxMD
  17. FitzGerald O, Ogdie A, Chandran V, et al. Psoriatic arthritis. Nat Rev Dis Primers. 2021; 7 (1): p.59. doi: 10.1038/s41572-021-00293-y . | Open in Read by QxMD
  18. Taylor W, Gladman D, Helliwell P, et al. Classification criteria for psoriatic arthritis: Development of new criteria from a large international study. Arthritis Rheum. 2006; 54 (8): p.2665-2673. doi: 10.1002/art.21972 . | Open in Read by QxMD
  19. Singh JA, Guyatt G, Ogdie A, et al. 2018 American College of Rheumatology/National Psoriasis Foundation Guideline for the Treatment of Psoriatic Arthritis. Arthritis & Rheumatology. 2018; 71 (1): p.5-32. doi: 10.1002/art.40726 . | Open in Read by QxMD
  20. Inamadar AC, Palit A, Ragunatha S. Textbook of Pediatric Dermatology. JP Medical Ltd ; 2014
  21. Hertl M. Autoimmune Diseases of the Skin: Pathogenesis, Diagnosis, Management. Springer Science & Business Media ; 2011

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