Psoriasis is a chronic inflammatory skin disorder that affects around half a million Australians. The condition is characterised by erythematous plaques, patches, and papules that often have a silvery scale. The underlying pathology of the condition involves hyperproliferation of keratinocytes in the epidermis. It normally takes at least 28 days for keratinocytes to maturate and shed. In psoriasis, keratinocytes mature and reach the surface of the skin in around four days. This high turnover rate results in the thickened plaques often seen in psoriasis.
There are five main types of psoriasis:
- Plaque psoriasis. This is the most common form, affecting around 80% to 90% of people with psoriasis. Raised, red patches covered with silvery scale often appear on the scalp, trunk, lower back, and extensor surfaces of the knees and elbows.
- Guttate psoriasis. This form affects around 10% of people with psoriasis and often starts in childhood or young adulthood. Small, red spots appear most commonly on the trunk and limbs. The face, scalp, and ears may also be affected. This form often develops suddenly after an initial trigger such as an upper respiratory tract infection with group A β-haemolytic streptococci. This type of psoriasis is the most likely to present with itch, which may be severe.
- Inverse psoriasis. Also known as intertriginous psoriasis. This form is less common and affects the flexural surfaces and skin folds. Due to its site of presentation, it may be mistaken for a fungal infection.
- Pustular psoriasis. This form is rarely observed in children. The condition usually occurs in cycles that include initial reddening of the skin followed by the appearance of white pustules and scaling. It may be distributed over large areas of the body or confined to the palms of the hands and soles of the feet.
- Erythrodermic psoriasis. This rare form affects only 3% of people with psoriasis. Flare-ups of erythrodermic psoriasis require immediate medical attention as the inflammation is often severe and widespread. Lesions are intensely red, and the pain and itching may be severe. Large areas of skin may shed which predisposes patients to secondary infections and fluid loss.
Although different types of psoriasis may require different therapeutic approaches, many patients experience symptoms that overlap between categories.
Psoriasis can appear at any age. However, initial presentation commonly occurs at 20 to 30 years of age with a secondary peak at 50 to 60 years of age. There is a strong hereditary component to the condition with around 30% of sufferers having a first-degree relative with the condition. In addition to the pruritus and discomfort of the skin lesions, psoriasis may also be associated with conditions such as arthritis, liver disease, cardiovascular disease, and the metabolic syndrome. Psoriatic arthritis is thought to affect 10% to 30% of those with psoriatic skin lesions. Joint involvement usually affects the hands and feet, but may also affect the large joints. Due to the chronic and very visual nature of this condition, psoriasis may also result in adverse psychosocial outcomes.
The choice of treatment modality is largely influenced by the type of psoriasis and the extent of disease. The amount of body surface area affected can be approximated using the palm of the hand. An area the size of the entire palmar surface equates to 1% body surface area. Patients with localised plaque psoriasis, often defined as affecting less than 5% of the total body surface area, can usually be managed with topical treatments and phototherapy. A dermatologist should be consulted in the case of other types of psoriasis and more extensive disease. For patients with moderate to severe psoriasis, systemic therapy is often required.
Corticosteroids, calcipotriol, and tazarotene form the cornerstone of the management of mild psoriasis. Other topical agents include tar products and keratolytic agents such as salicylic acid. These agents can be found in a number of over-the-counter products and may also be compounded by the pharmacy to the specifications of the treating physician. When topical agents and phototherapy are insufficient, systemic therapy by the oral, subcutaneous (SC), or intravenous (IV) route may be required. These medications can control symptoms for most patients with severe psoriasis. However, potential adverse effects limit the dose and duration of therapy for most of these medications. Table 1 provides an overview of some of the currently available treatment options.
Table 1. Treatment options for psoriasis
|Class||Medications||Usual Adult Dose||Usage||Precautions|
|Topical Corticosteroids||Hydrocortisone, betamethasone, mometasone, etc.||Varies by agent. Normally once or twice daily.||High-potency agents used for chronic lesions and hyperkeratotic areas (palms, soles).||Relapse occurs faster with topical corticosteroids than other topical therapies. Risk of rebound if treatment is abruptly discontinued.|
|Vitamin D Analogues||Calcipotriol||Apply to affected area twice daily.
Combination products with betamethasone are applied daily.
|Avoid use on face or skin folds – increased risk of irritation.||To prevent hypercalcaemia – limit weekly use to 100g calcipotriol-containing product per week for adults (50g for children 6-12 years, and up to 75g for children older than 12 years). Avoid occlusion.|
|Retinoid||Tazarotene||Apply a thin layer to lesions once daily. May start with 0.05% cream and increase to 0.1% if tolerated and required.||As effective as potent corticosteroids, although irritation may limit its use.||Do not use in pregnancy.|
|Phototherapy||Ultraviolet light B (UVB)
Psoralens + UVA (PUVA)
|Dose may vary according to skin type. Normally delivered three times a week.||Second-line therapy. Often combined with other therapies to reduce required exposure.||High cumulative doses of PUVA increase skin cancer risk. Risk uncertain with UVB therapy.|
|Retinoid||Acitretin||25-30mg orally daily for 2-4 weeks. Optimal results may be achieved with 25-50mg daily for a further 6-8 weeks.||Most effective when combined with phototherapy.||Adverse effects are common and mainly resemble excessive vitamin A exposure. Contraindicated during pregnancy and for women who may become pregnant within 2 years of treatment cessation. Avoid in women of childbearing potential.|
|Immunosuppressants||Methotrexate||Dose adjusted according to response.||Most common immunosuppressant used for psoriasis. Treatment may be continued long-term.||Monitoring required. Serious adverse effects such as myelosuppression, hepatotoxicity, nephrotoxicity, have occurred. Do not use in pregnancy.|
|Cyclosporin||2.5mg/kg per day in two divided doses. Dose may be increased to 5mg/kg per day.||Often clears lesions faster than methotrexate. Use normally, limited to 2 years to reduce risk of toxicity.||Potential adverse effects include nephrotoxicity, malignancy, hypertension, metabolic concerns.|
|Cytokine Modulators||Apremilast||30mg orally, twice daily (after initial titration).||Reserved for patients with severe psoriasis unresponsive to other therapies.||Comparative data is limited. Recent study suggests superior improvements in dermatology life quality index for ustekinumab compared to adalimumab, etanercept, and infliximab.|
|Secukinumab||300mg SC once weekly for 5 weeks, then monthly.|
|Ustekinumab||45mg SC at weeks 0 and 4, then every 12 weeks.|
|TNFα Antagonists||Adalimumab||80mg SC initially, then 40mg fortnightly.|
|Etanercept||50mg SC weekly.|
|Infliximab||5mg/kg IV at 0, 2, and 6 weeks, then every 8 weeks.|
Even after successful remission is achieved, rebound can occur after a therapy is ceased. Rebound psoriasis presents with increasingly unstable and more severe disease. Body areas that were previously unaffected may become involved, and the type of lesion may be different. The risk of rebound depends upon the treatment used. Topical corticosteroids and cyclosporin are more commonly associated with rebound effects, while it is less likely with phototherapy and biological therapies.
Psoriasis is a chronic condition that often requires life-long management. Appropriate daily skin care routines and avoidance of known triggers may help to prevent flare-ups. When active treatment is required, it should be tailored to the individual for maximum efficacy and reduced toxicity. It is also important to remember that this skin condition is associated with significant comorbidities. Therefore, a holistic approach is required in the management of psoriasis.
- Haggan M. First in new biologics class to treat psoriasis. Aust J Pharm. 2015.
- Mason AR, Mason J, Cork M, Dooley G, Hancock H. Topical treatments for chronic plaque psoriasis. Cochrane DB Syst Rev. 2013; CD005028.
- Rossi S, editor. Australian Medicines Handbook 2015 (online). Adelaide: Australian Medicines Handbook Pty Ltd; 2016.
- Strober BE, Bissonnette R, Fiorentino D, Kimball AB, Naldi L, Shear NH, et al. Comparative effectiveness of biologic agents for the treatment of psoriasis in a real-world setting: Results from a large, prospective, observational study (Psoriasis Longitudinal Assessment and Registry [PSOLAR]). J Am Acad Dermatol. 2016; 74(5): 851-61.
- Sullivan JR, Preda VA. Treatments for severe psoriasis. Aust Prescr. 2009; 32(1): 14-8.