Pruritus is a usual manifestation o...

Pruritus is a usual manifestation of dermatologic diseases, including xerotic eczema, atopic dermatitis, and allergic contact dermatitis. Effective treatment of pruritus can obviate scratch-induced complications such as lichen simplex chronicus and impetigo. Patients, particularly somewhat old adults, with severe pruritus that does not rejoin to conservative therapy should be evaluated for an underlying systemic disease. Causes of systemic pruritus include uremia, cholestasis, polycythemia vera, Hodgkin's lymphoma, hyperthyroidism, and human immunodeficiency virus (HIV) infection. Skin scraping, biopsy, or tillage may be indicated if skin lesions are near Diagnostic testing is directed at the clinical evaluation and may include a full blood count and measurement of thyroid-stimulating hormone, serum bilirubin, alkaline phosphatase, serum creatinine, and family urea nitrogen levels. Chest radiography and testing for HIV infection may be indicated in a certain patients. Management of nonspecific pruritus is directed mainly at preventing xerosis. Management of disease-specific pruritus has been established for certain systemic conditions, including uremia and cholestasis. (Am Fam Physician 2003;68:1135-421145-6 Copyright(c) 2003 American Academy of Family Physicians.)

Pruritus is a frequent dermatologic problem that increases in incidence with age. In any patients, the condition may be in the same manner severe that it affects drowse and quality of life. While pruritus principally commonly occurs in skin disorders, it may be an important dermatologic hint to the presence of an underlying systemic disease.

Pathophysiology

Pruritus originates within the skin's liberated nerve endings, which are in the greatest degree heavily concentrated in the wrists and ankles. The sensation of pruritus is transmitted [i]or[/i] part of to the other C fibers to the dorsal horn of the spinal cord and then to the cerebral cortex via the spinothalamic tract. (1) Pruritus generates a spinal reflective response, the scratch, which is as innate as a penetrating tendon reflex. (2) Regardless of the cause, pruritus frequently is exacerbated by skin inflammation, free from moisture or hot ambient conditions, skin vasodilation, and psychologic stressors. (3)

A single mechanism cannot explain all causes of pruritus. Histamine, which is released by the agency of mast cells in persons with urticaria and other allergic reactions, classically is associated with pruritus. However, with the exception of allergic conditions, histamine must be considered and nothing else one of several chemical mediators of itch.

Serotonin appears to be a tonic component of the pruritus that take places with several diseases, including polycythemia vera, uremia, cholestasis and lymphoma, and of morphine-associated pruritus. Serotonin inhibitors of the like kind as cyproheptadine (Periactin), pizotifen, paroxetine (Paxil), and ondansetron (Zofran) have prov effective in treating several of these pruritic conditions. (2)

Opioids trigger pruritus in as many as 90 percent of patients receiving intraspinal injections of narcotics. Intravenous and intradermal opioid injections also may induce itching. (2) Narcotic antagonists have been used favorably to relieve pruritus in patients with cholestasis. (4)

The pruritus that come into one's heads in herpes zoster prodrome may be a standard for pruritus with a neuropathic cause. Certain idiopathic images of localized pruritus have been attributed to peripheral neuropathy. Brachioradial pruritus is an odd condition that presents as lateral arm pruritus and has been associated with spinal disease. Similarly, notalgia paresthetica is meditation to be of neuropathic origin, with pruritus limited to the middle of the back. bitter pruritus also has been observ in patients with spinal tumors and multiple sclerosis. (256)

Atopic dermatitis appears to involve an immune-mediated release of cytokines and other pro-inflammatory agents, a mechanism analogous to airway hyperreactivity in patients with asthma. (7-9) Superimposed forward this hyperreactivity is a distorted touch sensation. Although patients without atopic dermatitis perceive mild mechanical stimulation as touch, patients with the condition perceive it as pruritus. (810)

Dermatologic Causes of Pruritus

XEROSIS

Pruritus mostly frequently is an unpleasant symptom of a clinically evident dermatologic condition (Table 1) (1-31112) The itch of thirsty skin, otherwise known as xerosis or asteatotic eczema, is for the use of all in older adults. (3,11,12) Xerosis come to one's minds most often during the winter in northern climates.

Patients with xerosis experience an intense pruritus, usually involving the anterolateral lower leg Other commonly involved areas include the back, flank, abdomen, and waist. Skin drying and scratching be the effect in red plaques that fissure and whose appearance has been compared to that of cracked porcelain (eczema craquele).

ATOPIC DERMATITIS

Atopic dermatitis can inference in severe pruritus and is frequently described as "the itch that rashes (when scratched)." Atopic dermatitis affects 10 percent of children and many times develops before six months of age. (79) Atopic dermatitis repeatedly persists into adulthood and may be exacerbated during pregnancy. Patients with atopic dermatitis usually have a family history of asthma and allergic rhinitis.