Psoriasis: A Comprehensive Overview


Psoriasis is a chronic inflammatory skin disease that is associated with a wide variety of comorbidities. It has also been considered a multisystem inflammatory disorder.


It has been found that the prevalence of psoriasis among adults varied between 0.5 and 11.4 percent, while it ranged between 0 and 1.4 percent among children. The prevalence of psoriasis appears to be the same for males and females


Risk factors

Several factors are implicated in the development of psoriasis.

  • The genetic predisposition is considered to be one of the most important factors. Psoriasis susceptibility is linked to a number of genes. A major genetic determinant of psoriasis is the PSORS1 locus on chromosome 6p21 of the major histocompatibility complex (MHC).
  • The development of psoriasis can be exacerbated or caused by a variety of medical conditions, behavioral conditions, and environmental exposures. These include smoking, obesity, and alcohol consumption. Additionally, there are several drugs that can worsen psoriasis or psoriasis-like drug eruptions, such as beta blockers, lithium, and antimalarial drugs. It has been shown that infections, both bacterial and viral, can worsen psoriasis. In patients with psoriasis, low vitamin D levels have been observed, but their role in the disease remains uncertain. Psoriasis is often attributed to stress as an underlying or exacerbating factor.



An important role is played by T lymphocytes, dendritic cells, and cytokines (IL-23, IL-17, and tumor necrosis factor [TNF]) in psoriasis, which leads to hyperproliferation and abnormal differentiation of the epidermis, inflammatory infiltrates, and vascular dilation.


Clinical features

  • Chronic plaque psoriasis is the most common form of psoriasis, characterized by well-defined, erythematous plaques with an overlying, coarse scale. Commonly affected areas include the scalp, extensor elbows, knees, and gluteal cleft.
  • A guttate psoriasis usually manifests as a sudden eruption of numerous small, inflammatory plaques.  Affected sites are mainly the trunk and proximal extremities.
  • Pustular psoriasis can manifest as acute, subacute, or chronic pustular eruptions and has life-threatening complications. A severe form of generalized pustular psoriasis (von Zumbusch-type) presents with widespread erythema, scaling, and superficial pustules.
  • An erythrodermic is an uncommon type of psoriasis that is characterized by skin erythema that usually affects most or all of the body surface.
  • Inverse psoriasis, as the name implies, affects the intertriginous areas, including the inguinal, perineal, genital, intergluteal, axillary, and inframammary regions. The lesions are well-demarcated, smooth, shiny plaques with a minimal to nonexistent scale.
  • Nail psoriasis often develops after the appearance of psoriatic skin lesions. However, it can also occur concurrently or before psoriasis develops in other areas. The typical nail abnormality is pitting, which appears as a few to multiple tiny pits scattered over the nail plate.
  • Psoriasis of the palms and soles is known as palmoplantar psoriasis. An erythematous, hyperkeratotic plaque with associated fissures is the classic presentation.

There are two classic signs of chronic plaque psoriasis: the Koebner phenomenon and the Auspitz sign. Koebner’s phenomenon describes the development of skin disease following skin trauma. Auspitz’s sign is characterized by pinpoint bleeding after the scaling overlying a plaque is removed.



Physical examination is the most reliable method of diagnosing chronic plaque psoriasis in the vast majority of patients who suffer from the disease. It is sometimes necessary to perform a skin biopsy, which can be helpful in challenging cases, but it is not usually necessary.



Psoriasis can be treated with a variety of topical and systemic treatments. It is important to consider the severity of the disease, relevant comorbidities, as well as the preferences of the patient when selecting treatment modalities

  • Limited plaque psoriasis:

Patients with limited plaque psoriasis should be treated initially with topical corticosteroids and emollients. Alternative treatments include tar, topical retinoids (tazarotene), topical vitamin D, and anthralin. In the case of facial or intertriginous areas, topical tacrolimus or pimecrolimus may be used.

  • Moderate to severe plaque psoriasis:

In most cases, it is advisable for most patients with moderate to severe plaque psoriasis to be initially treated with phototherapy.The use of systemic therapies may also be required. Commonly used medications include methotrexate and cyclosporine. Systemic corticosteroids are avoided due to the risk of severe withdrawal flare of psoriasis. In cases of severe psoriasis or psoriatic arthritis, biological therapy may be used.


Written by

Ghida Altammami, medical Student

Revised by

Maee Barakeh, medical student