What is psoriasis?

Psoriasis derives its name from the Greek word for 'itch'. It is a common, genetically determined, inflammatory and proliferative disease of the skin. It is characterized by a rapid buildup of rough, dry, dead skin cells forming thick scales. 

What causes it?

Normally, it takes about a month for new skin cells to move from the lowest layer of skin, where they form, to the outermost layer, where they die and scale off in flakes. In psoriasis, the life cycle of skin cells speeds up, resulting in a multitude of dead cells on the outermost layer of skin.

Incidence and Prevalence

The overall prevalence of psoriasis is about 1-3 %. It can occur suddenly at any age, but the onset is usually gradual and begins between ages 15 and 35. Psoriasis affects both sexes and all races.

Etiology 

The evidence that psoriasis may be inherited is beyond doubt, and rests on population surveys, twin and other family analyses and HLA studies. There has, however, been controversy over the mode of inheritance and researchers haven't yet been able to identify the gene or genes responsible for psoriasis.
It is common for psoriasis to run in families; approximately one-third of patients with psoriasis have a family member with the same condition.

Several other factors are important in provoking or exacerbating psoriasis;

1. Trauma; psoriasis worsens in areas of skin trauma (Koebner's phenomenon), so don't pick, scratch, or scrub the lesions and scales!
2. Infection; acute streptococcal infection precipitating guttate psoriasis.
3. Endocrine factors
4. Sunlight; although generally is beneficial for psoriasis, but it's better to avoid strong sunlight always!
5. Metabolic factors; hypocalcemia
6. Drugs; especially lithium, beta blockers and antimalarials . Also clonidine, iodides, glibenclamide, and tetracycline may exacerbate psoriasis
7. Psychogenesis factors

Clinical features

Psoriasis has several clinical expressions, but the most frequent type is psoriasis vulgaris, which occurs as chronic scaling papules and plaques in characteristic sites of the body, largely related to repeated minor trauma: scalp, elbows, forearms, lumbosacral region, knees, but usually not on the face.

Other variants of psoriasis are; erythrodermic psoriasis, generalized psoriasis, guttate psoriasis and pustular psoriasis.

Psoriasis only rarely affects general health apart from arthritis. Itching is usually mild. Once the problem starts, it usually continues although it may get better or worse over time and even seem to disappear for prolonged periods.

What is the usual course of psoriasis?

●             Psoriasis is unpredictable. It can come and go and has no known cure.

●             It tends to improve during the summer and worsen during the colder times of the year. These changes are probably a result of the positive influence of sunlight on psoriasis, except in sun sensitive/photosensitive individuals.

How is it diagnosed?

●             Most health care providers can usually easily recognize it by simply examining the skin.

●             If necessary, other tests, such as a skin biopsy can be performed to rule out other conditions.

Psoriatic Arthritis

About 10 percent of people with psoriasis develop psoriatic arthritis. Commonly they are adults in their 20s, 30s and 40s. Psoriatic arthritis is not accompanied by rheumatoid-type nodules, and has been classified into five clinical groups which often overlap.

Management

One of the things that make psoriasis so difficult to control is its wide variation in type, severity and response to treatment. There are some myths and facts about psoriasis that you should know;

1. At present there is no cure for psoriasis but it can often be completely cleared for periods of months or even years.
2. Every psoriatic patient presents an individual problem. Treatment depends upon age, sex, occupation, personality, general health, intelligence and resources as well as the type, extent, duration and natural history of the disease.
3. Psoriasis itself will not cause the hair to fall out.
4. There is no scientific evidence that homeopathic treatments are effective for treating psoriasis.

Topical Treatments

• Anthralin is made from the bark of a tree. Since it is an unstable product, combining with salicylic acid stabilizes it. It can be used in a thick ointment that is left on overnight night, sometimes under dressings, or applied in higher concentrations for 10-15 minutes before removal.
• Calcipotriene (Dovonex) is an ointment available by prescription that contains a derivative of vitamin D. Calcipotriene controls the overproduction of skin cells. It's a useful treatment for mild to moderate psoriasis. The main danger, apart from irritation is the possibility of increasing the level of calcium in the blood. This risk is reduced by limiting the amount used each day. The calcium level in the blood may be checked periodically if large quantities are required.
• Tar has been used for over one hundred years and is usually effective in treating psoriasis. Unfortunately, it can be smelly and stains clothing. Tars are made from the distillation of coal and wood. The cruder the tar extract, the more effective it is. Concentration of crude coal tar upto 10% are incorporated  in various vehicles for local treatment of psoriasis .Application is usually at night to minimise odour during the day. Tars can also make skin more sensitive to the sun, increasing the risk of sunburn.
• Corticosteroids are the commonest treatment for psoriasis and are helpful in reducing inflammation and irritation. The main problem is that the skin can become accustomed to the steroid over a period of time and with prolonged use of strong cortisone creams thinning of the skin can occur. Careful choice of the steroid and the use of appropriate treatment schedules will minimise risk of both of these problems.
• Vitamin D3
• PUVA

Systemic Treatments

• Methotrexate: In 1951,amethopterin (or methotrexate as it is more commonly known), a folic acid antagonist, was found to be excellent in the control of psoriasis. 20 years later, FDA approved it in psoriasis. It is an anticancer drug that blocks the growth of skin cells in psoriasis.
• Retinoids  are a group of drugs related to vitamin A. Retinoids reduce the proliferation of skin cells in cases of severe psoriasis. 
• Cyclosporine is a cyclic undecapeptide derived from fungus Toylypocladium inflatum gams. It is indicated for the treatment of adult non immuno-compromised patients with severe recalcitrant psoriasis who have failed to respond to at least one systemic therapy or in patients for whom other systemic therapies are contraindicated or cannot be tolerated.
• Hydroxyurea
• Photochemotherapy; Psoralen ultraviolet A (PUVA), a combination of light-sensitizing medications (psoralens) and ultraviolet A light, is effective in suppressing the growth of skin cells in severe psoriasis. However, long-term — 250 treatments or more — use of PUVA may increase your risk of melanoma, a deadly form of skin cancer. The higher risk begins about 15 years after the first PUVA treatment. Exposure to moderate sunlight — being careful to avoid sunburn — as well as the topical application of coal tar combined with ultraviolet radiation also are effective treatments. A form of phototherapy treatment called narrow-band ultraviolet B (UVB) has emerged in the past decade. This treatment may be as effective as PUVA but doesn't require that you take oral medications before each treatment. It's not suspected to carry as high a potential for skin cancer as PUVA.
• Biologics including Etanercept (Enbrel) and Infliximab (Remicade); Tumor necrosis factor (TNF-alfa) is a pro-inflammatory cytokine that is involved in many inflammatory disorders, including psoriasis and psoriatic arthritis. Recently , 2 types of TNF blockers have become available for clinical use: a soluble receptor (etanercept) and an anti-TNF-alfa monoclonal antibody (infliximab). Etanercept is a fusion protein consisting of a piece of the TNF receptor linked to the FC portion of human immunoglobulin G. This soluble protein exists as an immunoglobulin-like dimer that prevents TNF-alfa from binding to the cell-surface TNF-alfa receptor, thereby reducing the biological activity of TNF-alfa.
• Tacrolimus; a macrolide immunosuppressive isolated from streptomyces tsukubaensis act by inhibiting the keratonocyte receptor pathway, an endogenous regulator of the cell cycle. Topical application of the drug is promising in the initial pilot studies.
• Mycophenolate mofetil (MMF)
• Photodynamic therapy
• 308-nm Excimer laser