Psoriasis is one of the most common immune-mediated diseases world-wide. It is a chronic condition that waxes and wanes. Importantly it is not contagious but it can be an extremely painful, disfiguring and disabling condition for which there is no cure.
The exact causes of psoriasis have yet to be determined, however impairment of the immune system and genetics are known to play major roles in its development. When the immune system is somehow triggered it speeds up the growth cycle of skin cells among other immune reactions leading to a thickening of the skin, inflammation and excessive scaling.1
The prevalence of psoriasis in different populations varies between 0 and 12%, with estimates between 2 – 3% in most western populations. The prevalence in the northern most regions of the Russia and Norway ranges between 5–10% of the population and the highest 12% prevalence is found in the arctic population.2 In the U.S., prevalence ranges from 2.2% to 3.15% and the prevalence among African Americans is 1.3%. There is a low prevalence among North American Indians, Asians and Western Africans (0.3%). In Japan it is 0.1-0.2% of the population, in China 0.3% and is virtually undetected in Native South American Indians.3, 4, 5 Estimates of the prevalence of psoriasis in Australia ranges from 2.3% to 6.6% and in the U.K., the range was 1.3% to 2.6%.4,6 In Australia in the indigenous population it occur rarely, with two recent Australian studies reporting small numbers of Indigenous patients in both the urban and rural environment presenting with psoriasis.7
What triggers psoriasis is a complex question and a large number of factors are involved. Genes are important: numerous family studies have provided compelling evidence of a genetic predisposition to psoriasis, although the inheritance pattern remains unclear. The condition will develop in up to 50% of the siblings of persons with psoriasis when both parents are affected, but prevalence falls to 16% when only one parent has psoriasis and falls further to only 8% percent if neither parent is affected.8 Environmental risk factors also play a role: bacterial and viral infections, stress, skin trauma, smoking and obesity have all been associated with the onset and exacerbation of psoriasis.9
The classification of severity is based on several dermatological markers. It often is a combination of a PASI (Psoriasis Area and Severity Index) score and a BSA (Body Surface Area) coverage factor.
A PASI score is used by dermatologist to measure the dermatological markers to determine the severity and extent of psoriasis, especially during a clinical trial. Four body areas, the head, the arms, the torso and the legs, are measured according to redness (erythema), thickness (Induration/Infiltration) and scaling (Desquamation) from 0 to 4. (See Chart)
% coverage of the body affected is also involved in the classification of the severity of psoriasis. The classification of mild psoriasis is made when symptoms affect less than 3% of the body surface. Moderate psoriasis covers 3% – 10% and the classification of severe indicates that symptoms affects more than 10% of the body, also the involvement of the hands, feet, facial, or genital regions, by which, despite involvement of a smaller BSA, the disease may interfere significantly with activities of daily life. This of course does not take into account the emotional impact that the condition has on the sufferer.9
|Redness / Erythema|
Psoriasis can have a devastating impact on psychological well-being and social functioning, similar to that of cancer, arthritis, hypertension, heart disease, diabetes or depression. Most people with psoriasis suffer feelings of stigmatization because of their highly visible symptoms. This leads to feelings of social discrimination and alienation which compounds the feelings of anxiety and depression.9
Almost 90% of psoriasis sufferers have feelings of shame and embarrassment, 62% feel depressed, 58% suffer from anxiety, 44% feel that they have problems at work with most feeling that they are rejected for promotions, not accepted as part of the work group etc., 42% suffer from a lack of self-confidence due to their self-consciousness and 40% have difficulties in sexual relationships.10
TYPES OF PSORIASIS
Psoriasis has been classified into several different types10, depending upon presentation, including:-
- Plaque psoriasis or Psoriasis vulgaris (common type) – comprises approximately 90 percent of cases. Characterized by sharply demarcated erythematous silvery scaling plaques which most commonly occur on the extensor surface of the elbows, knees, scalp, sacral, and groin regions. The lesions are well-defined round or oval plaques that differ in size and in chronic plaque psoriasis that often coalesce to form very large, oddly shaped lesions covering large areas of the body. Other involved areas include the ears, glans penis, perianal region, and sites of repeated trauma.
- Scalp psoriasis is plaque psoriasis that is confined to the scalp, nape, forehead, sideburns, ears) the scalp lesions rarely extend > 2 cm beyond the hairline. Compared with plaque psoriasis elsewhere on the body, scalp involvement is frequently asymmetrical.
- Guttate psoriasis – numerous small, red or salmon pink, drop-like spots which cover a large portion of the skin. Spots have fine, slivery scale. Lesions are usually located on the trunk, arms and legs. Usually proceeded by a bacterial streptococcal infection (strep throat, chronic tonsillitis) or a viral respiratory infection.
- Flexural/intertriginous (Inverse psoriasis) – is located in the skin folds: i.e. armpits, under the breasts, skin folds around the groin and between the buttocks and in the skin fold of the obese. It is particularly subject to irritation from rubbing and sweating because of its location in the skin folds and tender areas. The plaques are thin, have minimal scale and a shiny surface commonly accompanied by secondary fissuring and/or maceration (the softening and breaking down of skin resulting from prolonged exposure to moisture). It is also prone to secondary infections such as tinea and candida.
- Palmoplantar psoriasis – presenting as hyperkeratotic (thickened), red or yellowish, scaly plaques on the central palm or weight-bearing areas of the soles. The lesions are well demarcated and often accompanied by painful cracking and fissuring.
- Palmoplantar pustulosis (PPP): is characterized by hyperkeratosis and clusters of pustules over the palms, and soles of hands and/or feet. These sterile pustules can remain as discrete pustules or may become confluent, producing lakes of pus which dry out, and the skin subsequently peels off, leaving a glazed, smooth erythematous surface. Quite often new crops of pustules will then appear.
- Pustular psoriasis or Generalized Pustular psoriasis (von Zumbusch type) – Pustular psoriasis may be localized clusters of pinhead sized sterile pustules or as in the Generalized presentation – the skin becomes very red and tender and within hours, pinhead-sized pustules appear studding the erythematous back? These painful, sterile pustules may become confluent, producing lakes of pus. Subsequently, the pustules dry out, and the skin peels off, leaving a glazed, smooth erythematous surface on which new crops of pustules may appear. This is usually accompanied by a fever and systemic symptoms e.g. nausea, and may require the patient to be hospitalized.
- Erythrodermic psoriasis – characterized by erythema, severe scaling, itching, and pain. This unstable psoriasis may some? times evolve to whole-body involvement that can lead to the inability to maintain homeostatic functions and often requires the patient to be hospitalized.
- Nail psoriasis – affecting the nails of the fingers and/or toes, may affect only one or several nails. The most frequent signs of nail psoriasis are pitting and distal onycholysis. Clinical manifestations range from pitting, yellowish discoloration, and paronychia, to subungual hyperkeratosis, onycholysis, and severe onychodystrophy.
- Psoriatic arthritis (PsA) a chronic inflammatory joint disease occurs in up to 39 % of patients with psoriasis. This type of arthritis can be slow to develop, with only mild symptoms or it can develop rapidly with extreme pain and characterized by focal bone erosions. PsA can be a severe form of arthritis with prognosis similar to that of rheumatoid arthritis
For more information on each classification of psoriasis refer to posts on each individual type.
- Višnja Milavec-Pureti? et al.; Drug Induced Psoriasis; Acta Dermatovenerol Croat 2011;19(1):39-42
- Bhalerao A., Bowcock A. M. ; The Genetics of Psoriasis: A Complex Disorder of the Skin and Immune System; Mol. Genet. (1998) 7 (10): 1537-1545 doi:10.1093/hmg/7.10.1537
- Kuchekar A.B. et al.; Psoriasis: A comprehensive review; Int. J. of Pharm. & Life Sci. (IJPLS), Vol. 2, Issue 6: June: 2011, 857-877 857
- Parisi R et al. Global epidemiology of psoriasis: A systemic review of incidence and prevalence. J Invest Dermatol 2012 Sep 27; [e-pub ahead of print]. (http://dx.doi.org/10.1038/jid.2012.339)
- Menter A., Stoff B.; Psoriasis – Chapter 1 History, Epidemiology and Pathogenesis; 2010; Manson Publishing UK.
- Parisi R. et al. Global Epidemiology of Psoriasis; Journal of Investigative Dermatology (2013), Volume 133
- Heyes C. et al.; Non-infectious skin disease in Indigenous Australians; Australasian Journal of Dermatology (2014) 55, 176–184
- Farber, E.M., Nall, L. and Watson, W. (1974) Natural history of psoriasis in 61 twin pairs. Arch. Dermatol., 109, 207–211.
- Pelle Stolt, Maglia Rotta; Bringing Psoriasis into the Light; International Federation of Pharmaceutical Manufacturers & Associations; http://www.ifpma.org/fileadmin/content/Publication/2014/Psoriasis_Publication-Web.pdf
- Zangeneh F.Z., Shooshtary F.S.; Psoriasis — Types, Causes and Medication – Chapter 1; http://cdn.intechopen.com/pdfs-wm/44173.pdf