Therapy For the Treatment of Psoriasis
- By:Robert Baird Baird
Diagnostic Presentation
Distribution: scalp, elbows, knees, gluteal fold
Koebner phenomenon
Nail pitting
Clinical hallmarks
Psoriasis is characterized by the presence of sharply marginated red plaques that are covered by copious amounts of white or silver scale. The scale is made up of fairly large flakes, some of which are large enough to grasp and strip off. Doing so may reveal underlying pinpoint spots of bleeding (Auspitz sign). Newly developed lesions are small (1- to 3-mm) papules but centrifllgal growth with coalescence of adjacent lesions results in the formation of large plaques some of which have a gyrate or serpiginous configuration.
Linear lesions are also often present. This linearity is a reflection of the Koebner phenomenon, wherein lesions preferentially arise at the site of cutaneous trauma. The Koebner phenomenon is highly distinctive, and it is found in only one other commonly encountered disease, lichen planus.
Lesions of psoriasis can occur anywhere on the body, but they are most commonly located on the scalp, elbows, and knees. The extensor surfaces of the arms and legs are also often involved. The presence of sharply marginated red plaques (with or without visible scale) in the gluteal fold and around the umbilicus is a very distinctive sign of psoriasis.
Nail changes are found in many patients. Early changes include nail plate pitting and onycholysis. Later changes include marked nail plate dystrophy and appreciable buildup of subungual, soft yellow keratin. The latter changes are very similar to those that occur in fungal infections of the nail, differentiation depends on KOH examination and fungal culture,
In most instances, the lesions of psoriasis are not pruritic, but those plaques that occur in the scalp and intertriginous folds are sometimes associated with considerable itching. A few patients, presumably those who are genetically atopic, will complain of generalized itching.
Atypical Clinical Presentatians
Very rarely the lesions in psoriatics become extensive enough to involve the entire body surface. In such instances, itching is often severe, and there is evidence of eczematization with weeping and crusting. Distinction from other forms of clinically similar exfoliative erythrodermatitis can be difficult unless certain features such as typical nail changes, seronegative arthritis, and a past history of more typical lesions, are present.
Children and young adults sometimes develop guttate psoriatics. This form of psoriasis is recognized by the sudden outbreak of hundreds of small, red, nonconf]uent papules. Scale fcmnation on these papules is often scanty. Plaque fcmnation is usually minimal, but a cardill search will usually reveal one or more slightly linear lesions as a result of the Koebner phenomenon. The appearance of guttate psoriasis is sometimes triggered by a preceding streptococcal infection. Children with guttate psoriasis sometimes experience long periods of complete remission after the initial episode has subsided.
Pustular psoriasis occurs in two forms that which involves primarily the palms and soles and is acompanied by nonpustular lesions of psoriasis elsewhere (barber type) and that which is completely generalized (Von Zurnbusch type). The latter often evolves into an exfoliative nythrodermatitis and is often accompanied by fever, anemia, Inlkocytosis, and general debilitation.
Course and Prognosis
Psoriasis is a lifelong, chronic disease characterized by exacerbations and remissions. Individual lesions tend to be in a constant state of flux. Plaques are continually growing, resolving, and changing in shape. The overall course of the disease is highly unpredictable. The patient's initial lesions after no clue as to the future course. Months of mild involvement may be followed by a period of severe flaring, halt sometimes the reverse occurs.
Little disability occurs as a result of the skin lesions, but "hout 10% of psoriatics develop arthritic changes. Many of these individuals will experience considerable pain and joint deformity,
Pathogenesis
The cause of psoriasis is unknown, but genetic factors play a role in the development of the disease. About 30% of psoriatic patients have a positive family history. Moreover, psoriatics share a significantly increased incidence of several HLA antigens. Immunologic factors are presumably also important (note the explosive development of psoriasis in some patients with acquired immunodeficiency syndrome (AIDS)), but no consistent explanation of specific immunologic abnormalities has as yet been elucidated.
Psoriatic lesions are characterized histologically by a remarkably expanded thickness of the epidermis (acanthosis) and by the presence of numerous neutrophils in the stratum corneum. The influx of these neutrophils is probably due to the presence of one or more leukotrienes (especially LTB4) with potent chemotactic properties within the stratum corneum.