Psoriasis
Psoriasis: Excerpt from Professional Guide to Diseases (Eighth Edition)
Psoriasis is a chronic, recurrent disease marked by epidermal proliferation. Its lesions, which appear as erythematous papules and plaques covered with silvery scales, vary widely in severity and distribution. Psoriasis is characterized by recurring partial remissions and exacerbations. Flare-ups are usually related to specific systemic and environmental factors but may be unpredictable; they can usually be controlled with therapy.
Causes and incidence
The tendency to develop psoriasis is genetically determined. Researchers have discovered a significantly higher-than-normal incidence of certain human leukocyte antigens (HLAs) 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 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 with 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.
Psoriasis affects approximately 2% of the population in the United States, and incidence is higher in whites than other races. Although this disorder is most common in young adults, it may strike at any age, including infancy.
Signs and symptoms
The most common complaint of the patient with psoriasis is itching and, occasionally, pain from dry, cracked, encrusted lesions. Psoriatic lesions are erythematous and usually form well-defined plaques, sometimes covering large areas of the body. (See Psoriatic plaques.) Such lesions most commonly appear on the scalp, chest, elbows, knees, shins, 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 frequently 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 shedding of scales is common in exfoliative or erythrodermic psoriasis and may also develop in chronic psoriasis.
Rarely, psoriasis becomes pustular, taking one of two forms. In localized pustular (Barber’s) psoriasis, pustules appear on the palms and soles and remain sterile until opened. In generalized pustular (von Zumbusch’s) psoriasis, which often 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.
In about 30% of patients, psoriasis spreads to the fingernails, producing small indentations and yellow or brown discoloration. In severe cases, the accumulation of thick, crumbly debris under the nail, causes it to separate from the nail bed.
Some patients with psoriasis develop arthritic symptoms (psoriatic arthritis), usually in one or more joints of the fingers or toes, 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 cutaneous manifestations of psoriasis; they demonstrate remissions and exacerbations similar to those of rheumatoid arthritis.
Diagnosis
Diagnosis depends on patient history, appearance of the lesions and, if needed, the results of skin biopsy. Typically, serum uric acid level is elevated as a result of accelerated nucleic acid degradation, but indications of gout are absent. HLA-Cw6, B-13, and B-w57 may be present in early-onset psoriasis. Sudden onset of psoriasis may be associated with human immunodeficiency virus.
Treatment
Treatment depends on the type of psoriasis, the extent of the disease and the patient’s response to it, and what effect the disease has on the patient’s lifestyle. No permanent cure exists, and all methods of treatment are merely palliative. Ideally, all patients should see a dermatologist at least once.
Removal of psoriatic scales necessitates application of occlusive ointment bases, such as petroleum jelly, salicylic acid preparations, or preparations containing urea. Baker P & S liquid (phenol, sodium chloride, and liquid paraffin), applied to the scalp at bedtime, or liquid carbonis detergens in Nivea oil applied for 6 to 8 hours, is also effective. Shampoo or tar-based preparations are also used. These medications soften the scales, which can then be removed by scrubbing them carefully with a soft brush while bathing. Some preparations, such as tar-based preparations, can be used in whirlpools for extensively involved areas.
Methods to retard rapid cell production include exposure to ultraviolet 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 twice daily, preferably after bathing to facilitate absorption, and 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, combined with a 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. Commonly used concurrently with steroids, anthralin is applied at night and steroids during the day.
In a patient with severe chronic psoriasis, the Goeckerman regimen — which combines tar baths and UVB treatments — may help achieve the longest remission and clear the skin in 3 to 5 weeks. The Ingram technique is a variation of this treatment, using anthralin instead of tar. A therapy called PUVA combines administration of psoralens with exposure to high-intensity UVA. As a last resort, a cytotoxin, usually methotrexate or cyclosporine, an immunosuppressant, may help severe, refractory psoriasis.
Etretinate, a retinoid compound, is effective in treating extensive cases of psoriasis. However, because this drug is a strong teratogen, it’s unsafe for use in women of childbearing age. It also has numerous adverse effects that many patients find intolerable. Tacarotene, a newer topical retinoid, combined with a medium-strength topical corticosteroid is also effective.
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; ketoconazole and anthralin may also be effective. No effective treatment exists for psoriasis of the nails.
Special considerations
Design your patient’s care plan to include patient teaching and careful monitoring for adverse effects of therapy.
❑ Make sure the patient understands his prescribed therapy; provide written instructions to avoid confusion. Teach 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. All topical medications, especially those containing anthralin and tar, should be applied with a downward motion to avoid rubbing them into the follicles. Gloves must be worn because anthralin stains and injures the skin. After application, the patient may dust himself with powder to prevent anthralin from rubbing off on his clothes. Warn the patient never to put an occlusive dressing over anthralin. Suggest 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 the patient use a soft brush to remove them.
❑ Watch for adverse effects, especially allergic reactions to anthralin, atrophy and acne from steroids, and burning, itching, nausea, and squamous cell epitheliomas from PUVA. 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 PUVA 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 isn’t contagious and, although exacerbations and remissions occur, they’re controllable with treatment. However, be sure he understands there’s no cure. Also, 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.
Pictures
Book Source Details
- Book Title: Professional Guide to Diseases (Eighth Edition)
- Author(s): Springhouse
- Year of Publication: 2005
- Copyright Details: Professional Guide to Diseases (Eighth Edition), Copyright © 2005 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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