Psoriasis- treatment, symptoms and cause of Psoriasis

Psoriasis is one of the most common dermatologic diseases, affecting up to 1 to 2% of the world's population. It is a chronic inflammatory skin disorder clinically characterized by erythematous, sharply demarcated papules and rounded plaques, covered by silvery micaceous scale. The skin lesions of psoriasis are variably pruritic. Traumatized areas often develop lesions of psoriasis (Koebner or isomorphic phenomenon). Additionally, other external factors may exacerbate psoriasis including infections, stress, and medications (lithium, beta blockers, and antimalarials).

The most common variety of psoriasis is called plaque type. Patients with plaque-type psoriasis will have stable, slowly growing plaques, which remain basically unchanged for long periods of time. The most common areas for plaque psoriasis to occur are the elbows, knees, gluteal cleft, and the scalp. Involvement tends to be symmetric. Inverse psoriasis affects the intertriginous regions including the axilla, groin, submammary region, and navel, it also tends to affect the scalp, palms, and soles. The individual lesions are sharply demarcated plaques but may be moist due to their location. Plaque psoriasis generally develops slowly and runs an indolent course. It rarely remits spontaneously.

Eruptive psoriasis (guttate psoriasis) is most common in children and young adults. It develops acutely in individuals without psoriasis or in those with chronic plaque psoriasis. Patients present with many small erythematous, scaling papules, frequently after upper respiratory tract infection with b-hemolytic streptococci. The differential diagnosis should include pityriasis rosea and secondary syphilis. Patients with psoriasis may also develop pustular lesions. These may be localized to the palms and soles or may be generalized and associated with fever, malaise, diarrhea, and arthralgias.

About half of all patients with psoriasis have fingernail involvement, appearing as punctate pitting, nail thickening, or subungual hyperkeratosis. About 5 to 10% of patients with psoriasis have associated joint complaints, and these are most often found in patients with fingernail involvement. Although some have the coincident occurrence of classic rheumatoid arthritis, many have joint disease that falls into one of three types associated with psoriasis:

(1) asymmetric inflammatory arthritis most commonly involving the distal and proximal interphalangeal joints and less commonly the knees, hips, ankles, and wrists;

(2) a seronegative rheumatoid arthritis-like disease; a significant portion of these patients go on to develop a severe destructive arthritis.

(3) disease limited to the spine (psoriatic spondylitis).

The etiology of psoriasis is still poorly understood. There is clearly a genetic component to psoriasis. Over 50% of patients with psoriasis report a positive family history, and a 65 to 72% concordance among monozygotic twins has been reported in twin studies. Psoriasis has been linked to HLA-Cw6 and, to a lesser extent, to HLA-DR7. Evidence has accumulated clearly indicating a role for T cells in the pathophysiology of psoriasis.

Stimulation of immune function with cytokines such as IL-2 has been associated with abrupt worsening of preexisting psoriasis, and bone marrow transplantation has resulted in clearance of disease. Psoriatic lesions are characterized by infiltration of skin with activated memory T cells, with CD8+ cells predominating in the epidermis. Agents that inhibit activated T cell function are often effective for the treatment of severe psoriasis. Presumably, cytokines from activated T cells elaborate growth factors that stimulate keratinocyte hyperproliferation.

Treatment of Psoriasis

Treatment of psoriasis depends on the type, location, and extent of disease. All patients should be instructed to avoid excess drying or irritation of their skin and to maintain adequate cutaneous hydration. Most patients with localized plaque-type psoriasis can be managed with midpotency topical glucocorticoids, although their long-term use is often accompanied by loss of effectiveness (tachyphylaxis). Crude coal tar (1 to 5% in an ointment base) is an old but useful method of treatment in conjunction with ultraviolet light therapy. A topical vitamin D analogue (calcipitriol) is also efficacious in the treatment of psoriasis.

Ultraviolet light is an effective therapy for patients with widespread psoriasis. The ultraviolet B (UV-B) spectrum is effective alone, or may be combined with coal tar (Goeckerman regimen) or anthralin (Ingram regimen). Natural sunlight or an artificial light source can be used. The combination of the ultraviolet A (UV-A) spectrum with either oral or topical psoralens (PUVA) is also extremely effective for the treatment of psoriasis, but long-term use may be associated with an increased incidence of squamous cell cancer and melanoma of the skin.

Various other agents can be used for widespread psoriatic disease. Methotrexate is an effective agent, especially in patients with associated psoriatic arthritis. Liver toxicity from long-term use limits its use to patients with widespread disease not responsive to less aggressive modalities.

The synthetic retinoid, acetretin, has been shown to be effective in some patients with severe psoriasis but is a potent teratogen, thus limiting its use in women with childbearing potential. The evidence implicating psoriasis as a T cell-mediated disorder has created a new perspective relating to the treatment of psoriasis. Based on this presumed disease mechanism, immunomodulatory therapy utilizing cyclosporine has proven to be highly effective in selected patients with severe, crippling, and potentially life-threatening disease.