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Introduction to Psoriasis Vulgaris
Overview
Psoriasis vulgaris is a chronic skin condition estimated to affect 2–4% of the population globally. It is characterised by sharply marginated patches of papules and plaques covered with silvery scales, and is often accompanied by itching (pruritus) and pain. Psoriasis often occurs in the teenage years, and is more prevalent in younger females. Psoriasis has a significant impact on quality of life due to physical appearance and time required to treat lesions and maintain clothing and bedding. The economic cost of psoriasis is substantial, including direct costs of management and indirect costs due to loss of productivity. Management in conventional medicine is determined by the severity of the disease, with topical agents used for mild disease and systemic agents used for severe disease. This chapter describes the risk factors for psoriasis, pathological process, diagnosis and severity assessment, and pharmacological and nonpharmacological management.
Psoriasis is a chronic, inflammatory and systemic disease that manifests most commonly as well-circumscribed, erythematous papules and plaques on the skin that are covered with silvery scales. Usually the skin lesions are pruritic and painful with adherent thick scales; removal of these scales may reveal pinpoint bleeding. The disease is a chronic recurring condition that varies in severity from minor localised patches to complete body coverage. Nails and joints can also be affected by psoriasis.1
Psoriasis is classified into seven categories: psoriasis vulgaris (plaque psoriasis), guttate psoriasis, inverse psoriasis, nail disease, psoriatic arthritis, pustular psoriasis and erythrodermic psoriasis (Table 1.1). Among these seven types, psoriasis vulgaris is the most common type of psoriasis, observed in approximately 80–90% of patients.1 Psoriasis vulgaris appears as sharply marginated, erythematous patches or plaques with a characteristic silvery-white micaceous scale. The plaques are round or oval in shape and are typically located on the scalp, trunk, buttocks and limbs, especially on extensor surfaces such as the elbows and knees.1
Table 1.1 Types of Psoriasis
| Psoriasis Types | Characteristics |
| Plaque psoriasis (psoriasis vulgaris) | Plaque psoriasis appears as sharply marginated, erythematous patches or plaques with a characteristic silvery-white micaceous scale. The plaques are round or oval in shape and are typically located on the scalp, trunk, buttocks and limbs, especially on extensor surfaces such as the elbows and knees. |
| Guttate psoriasis | Typical manifestation are dew-drop-like, 1–15-mm, salmonpink papules, usually with a fine scale. It is found primarily on the trunk and the proximal extremities. The disease is most common during childhood or adolescence and can transition into psoriasis vulgaris. |
| Inverse psoriasis | Inverse psoriasis commonly appears in the inframammary and abdominal folds, groin, axillae and genitalia. The lesions appear as erythematous plaques with small scales. |
| Nail disease | The characteristics of nail psoriasis include pitting, onycholysis, subungual hyperkeratosis and the oil-drop sign (a translucent discolouration in the nail bed that resembles a drop of oil beneath the nail plate). It is seen in 90% of patients with psoriatic arthritis. |
| Psoriatic arthritis | The characteristics of psoriatic arthritis are stiffness, pain, swelling and tenderness of the joints and surrounding ligaments and tendons (dactylitis and enthesitis). The radiographic features of psoriatic arthritis mainly involve joint erosion, joint space narrowing and bony proliferation. Nail damage is very common in psoriatic arthritis. |
| Pustular psoriasis | Pustular psoriasis consists of (i) generalised pustular psoriasis: shows widespread pustules often on an erythematous background and (ii) localised pustular psoriasis: presents as pustules on the palms of hands and/or soles of the feet. |
| Erythrodermic psoriasis | Chronic plaque psoriasis may develop into erythrodermic psoriasis. The patient’s entire body surface area may be covered with erythema accompanied by varying degrees of scaling, which may lead to hypothermia and dehydration. |
The prevalence of psoriasis varies considerably. It is reported that the average global prevalence of psoriasis is approximately 2–4%.2 The prevalence in cooler regions is higher than that of other regions.3 It has been suggested that the onset of psoriasis occurs at a younger age in female patients compared with males, which results in a higher prevalence in young females.4 Furthermore, the mean age of onset for the first presentation of psoriasis is between 15 and 20 years, with a second peak often occurring between 55 and 60 years, and then a significant decline after the age of 70 years, irrespective of gender.4
The cost of psoriasis vulgaris is considerable because of its longterm duration. Studies in Germany suggested that the average annual costs of mild psoriasis vulgaris per patient ranged from €500 to €2,000 and for severe disease from €4,000 to €10,000.5,6 The indirect cost was estimated to be about €1,600 per person per annum.6 A survey investigating patients with psoriasis in the UK indicated that an average psoriasis patient was absent from work for 26 days a year. In America, psoriasis costs US$11.3 billion in healthcare annually (when calculated at 2% prevalence) and the loss in productivity from psoriasis is around US$16.5 billion per year.7
Although psoriasis itself is not a life-threating condition, the physical and psychological comorbidities of psoriasis can significantly impair a patient’s quality of life.8–10 One study compared quality of life in people with psoriasis to people who have other diseases, and found that the decreased quality of life of patients with psoriasis was more severe than that of patients with diabetes, coronary heart disease and cancer.11 Besides the patient’s appearance, the amount of time required to treat extensive skin or scalp lesions and to maintain clothing and bedding adversely affects quality of life as well. In addition, arthritic psoriasis can also result in increasing and debilitating joint pain and stiffness and impaired movement.12
Risk Factors
The risk factors of psoriasis are not well defined. However, obesity is believed to be associated with psoriasis because usually patients have a higher body mass index compared with the non-psoriatic population.13 Smoking is likely to play a role in the onset of psoriasis14 and alcohol may influence the progression of the disease.15 Stress is an important trigger factor and may influence the development of the condition.16 Furthermore, some medications may be associated with the onset or exacerbation of psoriasis, including antimalarial medications, non-steroidal anti-inflammatory drugs (NSAIDs), B-blockers, lithium salts and withdrawal from steroids.17 Bacterial infections may also trigger or exacerbate psoriasis.17 Conversely, the consumption of fruit and vegetables, carrots, tomatoes and other food that are rich in b-carotene can decrease the risk of psoriasis.18
Pathological Processes
The aetiology and pathogenesis of psoriasis have not been completely defined but immune stimulation of epidermal keratinocytes is involved, where it triggers a complex immunological and inflammatory reaction.1 Currently, psoriasis is understood as an immune-mediated inflammatory diseas...
