Psoriasis is one of the most common skin diseases and affects approximately 1% (one percent) of the world population. Psoriasis is a chronic inflammatory disorder of skin.

Different varieties of psoriasis:

There are several different varieties of psoriasis such as plaque type (the most common variant of psoriasis), inverse psoriasis, guttate psoriasis (also called eruptive psoriasis) and pustular psoriasis.

Plaque type psoriasis:

This is the most common variant of psoriasis. The plaques of plaque type psoriasis remain stable for long time (plaques enlarge very slowly). The plaques of psoriasis are most commonly seen on elbow, knee, scalp and gluteal cleft. The lesions are generally symmetric. Remission occurs very rarely in plaque type psoriasis.

Inverse psoriasis:

Inverse psoriasis commonly occurs in axilla, groin, submammary region (in the folds of the breasts), and umbilical area, but can occur in the scalp, palms, and soles. The lesions are well demarcated. The plaques of inverse psoriasis may be moist and without scale due to their location.

Guttate psoriasis:

It is eruptive type of psoriasis and commonly seen among children and young adults. In children the guttate psoriasis develop acutely and commonly after upper respiratory tract infection with beta-hemolytic streptococci and have several small erythematous (red), scaling papules and may be mistaken for pityriasis rosea.

Pustular psoriasis:

Pustular psoriasis may be localized (to palms and soles) or generalized. The involved skin in pustular psoriasis is erythematous with presence of pustules and variable scale.

In generalized pustular psoriasis, it is commonly episodic in nature and episodes (fever and pustular episodea are recurrent) are characterized by fever (39°–40° C) which last for several days, with generalized eruption of sterile pustules, and a background of intense erythema. Local irritants, drugs, infections, and systemic glucocorticoid withdrawal, pregnancy etc. can precipitate this form of psoriasis.

The pustular psoriasis may be commonly mistaken for eczema due to location in palms and soles.

Other associated symptoms in psoriasis:

Approximately half of psoriasis patients have fingernail involvement, which appears as nail thickening, pitting of nail, onycholysis, or subungual hyperkeratosis. About 5–10% of patients have arthralgias (rheumatoid arthritis, psoriatic arthritis etc.). Arthralgias may cause asymmetric inflammatory arthritis which commonly involvs the interphalangeal joints (distal and proximal) and sometimes the knees, hips, ankles, and wrists.

What is the cause of psoriasis?

The cause of psoriasis is still not well understood. There is a strong genetic component of psoriasis as more than 50% of psoriasis patients have family history of psoriasis. Activated T-cells which infiltrate the psoriasis lesions release cytokines responsible for keratinocyte hyperproliferation and produce the characteristic clinical findings of psoriasis. T-cell activation is at least partially responsible for psoriasis, as demonstrated by effectiveness of agents inhibiting activation of T-cells in some cases of psoriasis. Psoriasis may be aggravated by factors such as infections, stress (traumatized areas can sometimes develop psoriasis) and medications (such as lithium, beta blockers, and antimalarials) etc.

Treatment of psoriasis:

The treatment of psoriasis depends on the type of psoriasis, extent of the disease and also location of the disease. The psoriatic location should not be allowed to dry and kep moist. The area also should be prevented from irritation.

If the psoriasis lesion is localized, in most patients can be managed with topical glucocorticoids of medium potency. But long-term use of topical glucocorticoids may cause atrophy (shrinkage) of skin and gradual loss of effectiveness (due to tachyphylaxis, which is loss of potency due to repeated application of a particular drug, as the patients develop tolerance to that drug). Calcipotriene (vitamin D analogue for topical use) and tazarotene (a retinoid or vitamin A analogue) are also effective in treating localized psoriasis, which have replaced commonly used topical agents such as coal tar, salicylic acid, and anthralin.

If psoriasis is widespread, natural or artificial ultraviolet light can be used. Ultraviolet B (UV-B) light including narrowband UV-B, and ultraviolet A (UV-A) with either oral or topical psoralens (PUVA) are highly effective in treatment of widespread psoriasis. Ultraviolet light should be used with caution as it can cause non-melanoma and melanoma skin cancer and it should be avoided in immunocompromised patients as the risk of skin cancer is very high.

Systemic agent Methotrexate (an antimetabolite) is used in treatment of widespread psoriasis. Methotrexate is highy effective in tteatment of psoriasis, especially in patients with psoriatic arthritis. Oral glucocorticoids are not be used (and should not be used) for the treatment of psoriasis, as there is potential for developing life-threatening pustular psoriasis when glucocorticoids therapy withdrawan. Synthetic retinoid such as acitretin also should be avoided as it is highly teratogenic. Methotrexate (antimetabolite), acitretin (retinoid) and cyclosporine (calcineurin inhibitor) are approved by USFDA for treatment of psoriasis.

Recent development in treatment of psoriasis:

As there evidence that psoriasis is T-cell mediated disorder, immunoregulation therapy is being tried e.g. cyclosporine and other immunosuppressive agents, which are quite effective in treatment of widespread psoriasis.

There are several biologic agents with more selective immunosuppressive properties and better safety profiles and they are being used these days. Some of the biologic agents which are approved for treatment of psoriasis are Alefacept (Anti-CD-2), Efalizumab (Anti CD-11a), Etanercept (anti Tumor Necrosis Factor-alpha or TNF-alpha), Adalimumab (anti TNF-alpha) and Infliximab (anti TNF-alpha). Anti Tumor Necrosis Factor-alpha may cause or worsen congestive heart failure (CHF), and they should not be used in CHF. These biologic agents with more selective immunosuppressive properties should not be given in presence of infection as they may worsen infection. As these are comperatively newer agents, the information regarding adverse effects are still emerging.