Psoriasis

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
Clinical features
Sharply demarcated, erythematous plaques with mica-like scale; predominantly elbows, knees, and scalp; atypical forms may localize to intertriginous areas; eruptive forms may be associated with infection.
May be aggravated by certain drugs, infection; severe forms seen associated with HIV
he most common variety of psoriasis is called plaque-type. Patients with plaque-type psoriasis will have stable, slowly enlarging plaques, which remain basically unchanged for long periods of time. The most commonly involved areas are the elbows, knees, gluteal cleft, and the scalp. Involvement tends to be symmetric. Plaque psoriasis generally develops slowly and runs an indolent course. It rarely remits spontaneously. Inverse psoriasis affects the intertriginous regions including the axilla, groin, submammary region, and navel; it also tends to affect the scalp, palms, and soleGuttate psoriasis (eruptive 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 -hemolytic streptococci. The differential diagnosis should include pityriasis rosea and secondary syphilis.The other types of psoriasis is pustular psoriasis. About half of all patients with psoriasis have fingernail involvement, appearing as punctate pitting, onycholysis, nail thickening, or subungual hyperkeratosis. About 5–10% of patients with psoriasis have associated arthralgias, and these are most often found in patients with fingernail involvement. Although some have the coincident occurrence of classic rheumatoid arthritis (Chap. 314), many have psoriatic arthritis that falls into one of three types: (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; or (3) disease limited to the spine (psoriatic spondylitis).
Treatment:
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) and atrophy of the skin. A topical vitamin D analogue (calcipotriene) and a retinoid (tazarotene) are also efficacious in the treatment of limited psoriasis and have largely replaced other topical agents such as coal tar, salicylic acid, and anthralin.
Ultraviolet light, natural or artificial, is an effective therapy for many patients with widespread psoriasis. Ultraviolet B (UV-B) light, narrowband UV-B, and ultraviolet A (UV-A) spectrum with either oral or topical psoralens (PUVA) are also extremely effective. The long-term use of UV light may be associated with an increased incidence of non-melanoma and melanoma skin cancer. UV light therapy is contraindicated in patients receiving cyclosporine and should be used with great care in all immunocompromised patients due to an increased risk of developing skin cancers.
The FDA approved systemic agents used for psoriasis are methotrexate, Acitretin & Cyclosporine.Etanercept & Infliximab are monoclonal antibodies against TNF alpha which are used in psoriasis