Psoriasis is a chronic, recurrent disease, marked by epidermal proliferation. Its lesions, which appear as erythematous papules and plaques covered with silver scales, vary widely in severity and distribution. Psoriasis affects about 21% of the population in the United States.
Although this disorder commonly affects young adults, it may strike at any age, including during infancy. Psoriasis is characterized by recurring partial remissions and exacerbations. Flare-ups are commonly related to specific systemic and environmental factors but may be unpredictable; they can usually be controlled with therapy.
The tendency to develop psoriasis is genetically determined. Researchers have discovered a significantly higher-than-normal incidence of certain human leukocyte antigens (HLA) in families with psoriasis, suggesting a possible immune disorder. Onset of the disease is also influenced by environmental factors.
Trauma can trigger the isomorphic effect or Koebner’s phenomenon, in which lesions develop at sites of injury. Infections, especially those resulting from beta-hemolytic streptococci, may cause a flare-up of guttate (drop-shaped) lesions. Other contributing factors include pregnancy, endocrine changes, climate (cold weather tends to exacerbate psoriasis), and emotional stress.
Generally, a skin cell takes 14 days to move from the basal layer to the stratum corneum, where after 14 days of normal wear and tear, it’s sloughed off. The life cycle of a normal skin cell is 28 days, compared to only 4 days for a psoriatic skin cell. This markedly shortened cycle doesn’t allow time for the cell to mature. Consequently, the stratum corneum becomes thick and flaky, producing the cardinal manifestations of psoriasis.
The most common complaint of the patient with psoriasis is itching and occasional pain from dry, cracked, encrusted lesions.
Psoriatic lesions are erythematous and usually form well-defined plaques, sometimes covering large areas of the body. (See Viewing psoriasis.) Such lesions usually appear on the scalp, chest, elbows, knees, back, and buttocks.
The plaques consist of characteristic silver scales that either flake off easily or can thicken, covering the lesion. Removal of psoriatic scales typically produces fine bleeding points (Auspitz sign). Occasionally, small guttate lesions appear, either alone or with plaques; these lesions are typically thin and erythematous, with few scales.
Widespread involvement of scales and erythema is called exfoliative or erythrodermic psoriasis. In about 60% of patients, psoriasis spreads to the fingernails, producing small indentations or pits and yellow or brown discoloration. In some cases, the accumulation of thick, crumbly debris under the nail causes it to separate from the nail-bed (onycholysis).
Rarely, psoriasis becomes pustular, taking one of two forms. In localized pustular psoriasis, pustules appear on the palms and soles and remain sterile until opened. In generalized pustular (Von Zumbusch) psoriasis, which commonly occurs with fever, leukocytosis, and malaise, groups of pustules coalesce to form lakes of pus on red skin. These pustules also remain sterile until opened and commonly involve the tongue and oral mucosa.
Some patients with psoriasis develop arthritic symptoms, usually in one or more joints of the fingers or toes, in the larger joints, or sometimes in the sacroiliac joints, which may progress to spondylitis. Such patients may complain of morning stiffness. Joint symptoms show no consistent linkage to the course of the cutaneus manifestations of psoriasis; they demonstrate remissions and exacerbations similar to those of rheumatoid arthritis.
Diagnosis depends on patient history, appearance of the lesions and, if needed, the results of skin biopsy. In severe cases, the serum uric acid level is typically elevated due to accelerated nucleic acid degradation; however, indications of gout are absent. HLA antigens may be present in early-onset familial psoriasis.
Appropriate treatment depends on the type of psoriasis, the extent of the disease and the patient’s response to it, and the effect the disease has on the patient’s lifestyle. No permanent cure exists, and all methods of treatment are palliative.
Methods to retard rapid cell production include exposure to ultraviolet (UV) light (UVB or natural sunlight) to the point of minimal erythema. Tar preparations or crude coal tar itself may be applied to affected areas about 15 minutes before exposure or may be left on overnight and wiped off the next morning.
A thin layer of petroleum jelly may be applied before UVB exposure (the most common treatment for generalized psoriasis). Exposure time can increase gradually. Outpatient or day treatment with UVB prevents long hospitalizations and prolongs remission.
Steroid creams and ointments are useful to control psoriasis. A potent fluorinated steroid works well, except on the face and intertriginous areas. These creams require application two times a day, preferably after bathing to facilitate absorption, and the overnight use of occlusive dressings, such as plastic wrap, plastic gloves or booties, or a vinyl exercise suit (under direct medical or nursing supervision).
Small, stubborn plaques may require intralesional steroid injections. Anthralin ointment or paste mixture may be used for well-defined plaques but must not be applied to unaffected areas because it causes injury and stains normal skin. Apply petroleum jelly around the affected skin before applying anthralin. Typically used with steroids, anthralin is applied at night and steroids during the day. A new topical agent is calcipotriene ointment, a vitamin D3 analogue.
CLINICAL TIP: Calcipotriene treatment also works best when alternated with a topical steroid, as noted above with anthralin.
Low-dose antihistamines, oatmeal baths, emollients, and open wet dressings may help relieve pruritus. Aspirin and local heat help alleviate the pain of psoriatic arthritis; severe cases may require nonsteroidal anti-inflammatory drugs.
Therapy for psoriasis of the scalp consists of a tar shampoo followed by application of a steroid lotion. No effective topical treatment exists for psoriasis of the nails.
❑ Design your care plan to include patient teaching and careful monitoring for adverse reactions to therapy.
❑ Make sure that the patient understands his prescribed therapy; provide written instructions to avoid confusion.
❑ Teach the correct application of prescribed ointments, creams, and lotions. A steroid cream, for example, should be applied in a thin film and rubbed gently into the skin until the cream disappears.
❑ Warn the patient never to put an occlusive dressing over anthralin. Suggest the use of mineral oil, then soap and water, to remove anthralin.
❑ Caution the patient to avoid scrubbing his skin vigorously, to prevent Koebner’s phenomenon. If a medication has been applied to the scales to soften them, suggest that the patient use a soft brush to remove them.
❑ Watch for adverse reactions, especially allergic reactions to anthralin, atrophy and acne from steroids, and burning, itching, nausea, and squamous cell epitheliomas.
❑ Initially evaluate the patient on methotrexate weekly, then monthly for red blood cell, white blood cell, and platelet counts because cytotoxins may cause hepatic or bone marrow toxicity. Liver biopsy may be done to assess the effects of methotrexate.
❑ Caution the patient receiving therapy to stay out of the sun on the day of treatment, and to protect his eyes with sunglasses that screen UVA for 24 hours after treatment. Tell him to wear goggles during exposure to this light.
❑ Be aware that psoriasis can cause psychological problems. Assure the patient that psoriasis is not contagious and that any exacerbations and remissions that occur are controllable with treatment. However, make sure that he understands that there is no cure for psoriasis.
❑ Because stressful situations tend to exacerbate psoriasis, help the patient learn to cope with these situations.
❑ Explain the relationship between psoriasis and arthritis, but point out that psoriasis causes no other systemic disturbances.
❑ Refer all patients to the National Psoriasis Foundation, which provides information and directs patients to local chapters.
Review other book chapters online related to Psoriasis:
Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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More About This Book:
Title: Handbook of Diseases Authors: Springhouse Publisher: Lippincott Williams & Wilkins Copyright: 2003 ISBN: 1-58255-266-5 
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