General information of psoriasis in Western Medicine.docx

1、General information of psoriasis in Western MedicineGeneral information of psoriasis in Western Medicine1.1 Definition of psoriasisPsoriasis is a chronic, inflammatory and systemic disease that manifests most commonly as well-circumscribed, erythematous papules and plaques on the skin that are cover

2、ed 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 ca

3、n also be affected by psoriasis (1).1.2 Pathology and pathogenesis of psoriasisThe etiology and pathogenesis of psoriasis has not been completely defined but it involves immune stimulation of epidermal keratinocytes. It involves a complex immunological and inflammatory reaction (1). The pathogenesis

4、 of psoriasis has a large hereditary component. At least eight chromosomal loci have been identified for which statistically significant evidence for linkage to psoriasis has been observed (these loci are known as psoriasis susceptibility (PSORS) 1 to 8) (1). Of these chromosomal loci, the human leu

5、kocyte antigen (HLA-Cw6 allele/ HLA-Cw0602Cw0613), also known as PSORS1, is the key susceptibility gene for psoriasis (2). In addition to genetic factors, environmental factors including infection, smoking, medications (e.g. beta blockers, nonsteroidal anti-inflammatory drugs (NSAIDs ), antimalarial

6、s, terbinafine, calcium channel blockers, lipid-lowering drugs, etc), skin injury (Koebners phenomenon) and stress are thought to evoke an inflammatory response and subsequent hyperproliferation of keratinocytes, resulting in psoriasis (1, 3).The development of psoriasis is thought to involves the f

7、ollowing process: T-cells activate and migrate into the skin after elements of the innate immune system are activated (keratinocytes and dendritic cells) (3, 4); Functional T-cells including type 1 helper T cells (Th1) and type 17 helper T cells (Th17) grow under the influence of cytokines such as i

8、nterleukin 12 (IL-12) and interleukin 23 (IL-23) (3, 4); Pro-inflammatory cytokines such as tumour necrosis factor- (TNF-), IL-17 and IL-22 are secreted by Th1 and Th17 cells promoting the inflammatory process in psoriasis (3, 4); Local skin cells including endothelial cells, fibroblasts, and kerati

9、nocytes enhance the cutaneous immune response through expression of adhesion molecules and other mediators (3, 4). Overall, psoriasis is an immune-mediated organ-specific (skin, and/or joint) inflammatory disease in which intralesional inflammation primes basal stem keratinocytes to hyperproliferate

10、 and perpetuate the disease process (3, 4).1.3 Epidemiology of psoriasis1.3.1 Prevalence of psoriasis in global general populationAlthough psoriasis occurs worldwide, its prevalence varies considerably (5). It is reported that the average global prevalence of psoriasis is approximately 3%4%. About 1

11、5%-30% of psoriasis sufferers have the sequelae psoriatic arthritis, equating to approximately 0.5%1% of the total population (6). Table (chapter 1-1) presents the prevalence data reported in recent surveys. Table (chapter 1-1) Prevalence of psoriasis by country Country% with psoriasisSample sizeChi

12、na (7)0.4717, 345UK (8)1.97, 520, 293France (9)5.26, 887Norway (10)8.518, 747USA (11)2.227, 220USA (12)3.152, 984USA (Caucasian population) (13)2.521, 921USA (African population) (13)1.32, 443Australia (Victoria) (14)6.61, 4571.3.2 Factors impacting on the prevalence of psoriasisThe reported prevale

13、nce surveys differ in many regards, namely geographical origin of the study, definition of prevalence on time point, period, and lifetime of psoriasis, sampling methods, and whether it is self-reported or diagnosis confirmed by physician. Most of these studies are based on self-reported diagnosis, w

14、hich may leave mild cases of psoriasis, e.g. nail disease, undiagnosed. Moreover, the elusive aetiology of skin diseases and the lack of precise classification criteria for psoriatic arthritis may also lead to misdiagnosis (6). Geographic and ethnic factors also contribute to differences in psoriasi

15、s prevalence. For instance, the prevalence in cooler regions is higher than that of other regions (15). In addition, lower prevalence is observed among African Americans (1.3%), compared with the Caucasian American population (2.5%) (13). Multi-factorial components such as physical environment, gene

16、tic factors, gender, age and behavioural patterns play a role in the progression of psoriasis (15). 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 female patients (16). Furthermore, the m

17、ean age of onset for the first presentation of psoriasis is between 1520 years, with a second peak often occurring between 5560 years, and then a significant decline after the age of 70 years, irrespective of gender (16).1.3.3 Risk factors of psoriasisThe risk factors of psoriasis are not well defin

18、ed. However, obesity is believed to be associated with psoriasis as patients have a higher body mass index compared with the non-psoriatic population (17). Smoking is likely to play a role in the onset of psoriasis (18) and alcohol may influence the progression of the disease (19). Stress is an impo

19、rtant trigger factor and may influence the development of the condition (20). Furthermore, some medications may be associated with the onset or exacerbation of psoriasis, including antimalarial medications, NSAIDs, -blockers, lithium salts and withdrawal from steroids (21). Bacterial infections may

20、also trigger or exacerbate psoriasis (21). Conversely, the consumption of fruit and vegetables, carrots, tomatoes and -carotene can decrease the risk of psoriasis (22).1.3.4 Impact of psoriasis1.3.4.1 Quality of lifePsoriasis itself is not a life-threating condition however, it has a significant imp

21、act on the sufferers quality of life. The psychological comorbidities of psoriasis can significantly impair a patients quality of life (23-25). One study compared quality of life in people with psoriasis with people who have other diseases, and found that the quality of life of patients with psorias

22、is was more severe than that of patients with diabetes, coronary heart disease and cancer (26). Besides the patients 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

23、 psoriasis can also result in increasing and debilitating joint pain and stiffness and impaired movement (27) .1.3.4.2 Economic burdenGenerally, the cost of disease consists of direct costs including diagnostic procedures, therapies and hospital admissions and indirect costs including work absenteei

24、sm, early retirement, and unemployment. The cost of psoriasis is considerable because of its long-term 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 to10, 000 (28, 29). The indire

25、ct cost was estimated to be about 1,600 per person per annum (29). A survey investigating patients with psoriasis in the United Kingdom indicated that an average psoriasis patient was absent from work for 26 days a year. In America, psoriasis costs US$11.3 billion in health care annually (when calcu

26、lated at 2% prevalence) and the loss in productivity from psoriasis is around US$16.5 billion per year (30).1.4 Diagnosis of psoriasis1.4.1 Types of psoriasisPsoriasis is classified into seven categories:1. Plaque psoriasis (psoriasis vulgaris)Plaque psoriasis is the most common type of psoriasis, o

27、bserved in approximately 80% to 90% of patients (1). Plaque psoriasis appears as sharply marginated, erythematous patches or plaques with a characteristic silvery-white micaceous scale (31). The plaques are round or oval in shape and are typically located on the scalp, trunk, buttocks and limbs, esp

28、ecially on extensor surfaces such as the elbows and knees (1). 2. Guttate psoriasisTypical manifestation is dew-drop-like, 1 to 15 mm, salmon-pink papules, usually with a fine scale. It is found primarily on the trunk and the proximal extremities. A history of upper respiratory infection with group

29、A beta-hemolytic streptococci often precedes guttate psoriasis. The disease is most common during childhood or adolescence and can transition into psoriasis vulgaris (1, 3). 3. Inverse psoriasisInverse psoriasis commonly appears in the inframammary and abdominal folds, groin, axillae, and genitalia.

30、 The lesions appear as erythematous plaques with small scales (1, 3).4. Nail diseaseThe 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).

31、Nail psoriasis usually affects nails on the hands more often than the feet. It is seen in 90% of patients with psoriatic arthritis (1).5. Psoriatic arthritisPsoriatic arthritis is an inflammatory seronegative spondyloarthropathy associated with psoriasis. The characteristics of psoriatic arthritis a

32、re stiffness, pain, swelling, and tenderness of the joints and surrounding ligaments and tendons (dactylitis and enthesitis). The severity of the arthritis usually does not correlate with the skin disease. Nail damage is very common in psoriatic arthritis. The radiographic features of psoriatic arthritis mainly involve joint erosion, joint space narrowing, and bony proliferation (32).6. Pustular psoriasis Pustular psoriasis consists of generalised and localised types. Generalised pustular psoriasis shows widespread