Psoriasis

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What is Psoriasis?

Psoriasis is a chronic dermatological condition characterized by pruritic erythematous patches and silvery scales, with symptom severity varying from mild to severe.

In normal skin, the cells are normally replaced every three to four weeks; however, in individuals with psoriasis, this process is accelerated, occurring within approximately three to seven days. Consequently, this rapid proliferation of skin cells leads to a buildup of skin layers and the manifestation of various symptoms associated with psoriasis.

 

Risk factors of Psoriasis

Risk factors for developing psoriasis include:

  • Family History
  • Infections: Viral infections (like HIV) and bacterial infections (such as strep throat) can trigger psoriasis
  • Psychological Stress
  • Obesity
  • Smoking

 

Causes of Psoriasis

The etiology of psoriasis is not yet fully understood but involves a combination of genetic, immune, and environmental factors Key triggers can include:

  • Skin trauma
  • Psychological stress
  • Infections, notably streptococcal throat infections
  • Smoking 
  • Certain medications

 

Clinical features of Psoriasis

The disease typically follows a relapsing course characterized by intervals of symptom-free periods. It is characterized by well-defined erythematous plaques and/or papules with silver-white scaling. Initial presentations often consist of solitary lesions, which may subsequently merge to form larger confluent areas. These lesions predominantly occur on the scalp, trunk, elbows, and knees—typically the extensor surfaces—though any area of the skin may be involved. Pruritus is reported in approximately 80% of cases, generally mild but occasionally severe.

Characteristic features include:

Auspitz sign, which refers to pinpoint bleeding that occurs upon the removal of scales, revealing dermal papillae.

Additionally, the Koebner phenomenon describes the occurrence of psoriatic lesions on previously unaffected skin in response to physical stimuli or skin injury, such as trauma, scratching, or the friction of irritating clothing, reflecting an isomorphic response. Nail involvement occurs in approximately 50% of cases.

Common manifestations include:

  • Nail pitting: characterized by small, round depressions on the nail surface.
  • Brittle nails: which exhibit dystrophy and crumbling.
  • Onycholysis: defined as partial separation of the nail plate, predominantly at the distal edge.
  • Oil drop sign (or salmon spot): presents as a well-circumscribed yellow-red discoloration of the nail.

 

Types of Psoriasis

  •  Plaque Psoriasis: This is the most prevalent variant, characterized by symmetrically distributed, thick erythematous lesions covered with silvery scales.
  •  Guttate Psoriasis: This variant features lesions resembling the size of drops of water and may progress to plaque psoriasis. It primarily occurs in children and adolescents, often following a streptococcal infection.
  •  Erythrodermic Psoriasis: This form presents as generalized erythematous lesions accompanied by diffuse scaling. It has the potential to lead to severe health complications, including fever and dehydration.
  • Inverse Psoriasis: This variant predominantly affects skin folds and the flexural creases of large joints, commonly referred to as flexural psoriasis.
  •  Pustular Psoriasis: There is a significant association with HLA-B27, with generalized pustular psoriasis being the most common subtype. This variant is characterized by generalized erythroderma and the presence of confluent white pustules over the entire body, potentially involving the oral mucosa and tongue. It typically exhibits a relapsing course, accompanied by pronounced malaise, including fever, weakness, and chills, and can be life-threatening.

 

Health conditions associated with psoriasis

  • Psoriatic Arthritis
  • Spondyloarthropathy
  • Inflammatory Bowel Disease: Includes Crohn’s disease and ulcerative colitis.
  • Uveitis
  • Coeliac Disease
  • Localised palmoplantar pustulosis, generalised pustulosis, and acute generalised exanthematous pustulosis
  • Non-Alcoholic Fatty Liver Disease
  • Metabolic Syndrome

 

Diagnosis of Psoriasis

Psoriasis is a clinical diagnosis based on the patient’s medical and familial history, along with a detailed examination of the skin. Skin biopsy is indicated primarily in cases where the clinical presentation is atypical.

Supporting histological findings include:

  • Acanthosis and parakeratosis
  • Thickening of the stratum spinosum with thinning of the stratum granulosum
  • Presence of Munro microabscesses, which are characterized by the accumulation of neutrophils within the stratum corneum, surrounded by parakeratosis.

 

Treatment of Psoriasis

Psoriasis currently has no cure; however, symptoms can be effectively managed through various medications tailored to the type, severity, and location of the lesions.

1- Topical therapies:

Mild psoriasis is typically managed with topical agents. Common treatments include:

  • Emollients and moisturizers
  • Coal tar preparations
  • Dithranol treatments
  • Salicylic acid
  • Vitamin D derivatives (such as calcipotriol)
  • Topical steroids
  • Combination ointment/gel or foam of calcipotriol and betamethasone dipropionate
  • Calcineurin inhibitors (like tacrolimus and pimecrolimus)

2- Phototherapy

3- Systemic therapies:

For moderate to severe psoriasis, treatment typically involves systemic agents and/or phototherapy. The most commonly used systemic treatments include:

  • Methotrexate
  • Ciclosporin
  • Acitretin

Additionally, other medications that are sometimes used for psoriasis are:

  •  Apremilast
  • Hydroxyurea
  • Dimethyl fumarate

4- Biologic therapies: 

Biologic therapy is specifically used for severe cases of psoriasis and psoriatic arthritis that do not respond to standard systemic treatments.

 

 

Written by:

Atheer Alhuthaili, Medical Intern.

Revised by: 

 Naif Alshehri, Medical Intern

References:

DermNet.

Amboss 

Medscape 

MOH