Pruritus
Beverly A. VonderPool
Approach
Pruritus, a sense of the need to scratch, is an unpleasant cutaneous sensation that has numerous causes. A practical approach is to look for causes with the highest probability first; generally, pruritus is caused by a primary skin disorder instead of a systemic disorder. The itching can be localized or generalized, mild or sufficiently severe to impair sleep. Pruritus can be classified as primary (nonspecific or specific) or secondary to a systemic disease. The main disorders include (1):
A. Primary skin disorders with nonspecific or inconspicuous eruption include aquagenic pruritus, atopic dermatitis, bullous pemphigoid, contact dermatitis, dermatitis herpetiformis, fiberglass dermatitis, insect bites, miliaria (prickly heat), pediculosis (lice), scabies, urticaria (hives), and xerosis (dry skin).
B. Primary skin disorders with specific or apparent eruptions include drug reactions, folliculitis, fungal infections, lichen planus, lichen simplex chronicus, mycosis fungoides, pemphigus foliaceus, pityriasis rosea, pruritic urticarial papules and plaques of pregnancy, psoriasis, and sunburn.
C. Pruritus associated with systemic disease includes acquired immune deficiency syndrome (AIDS), biliary disease caused by drugs, pregnancy or cirrhosis, chronic renal failure, hyperthyroid disease, lymphoreticular disorders (Hodgkin’s and non-Hodgkin’s lymphoma), psychiatric disease, and visceral malignancy.
D. Most common causes and concerns. Xerosis (dry skin) is the most common cause of generalized pruritus in both the young and the old (2,3). Chronic renal failure is the systemic disorder most commonly associated with secondary pruritus. Although malignancy is of concern in the patient with chronic pruritus, associated malignancy occurs in less than 1% of patients referred to a dermatologist (1,4).
History
The history frequently suggests whether the pruritus is primary or secondary, and often provides clues to its cause. In taking the history, ascertain the location and duration of the pruritus, exacerbating and alleviating factors, and the patient’s medications, occupation, travel, bathing habits, and family history of atopy or cancer. Also ask about possible pregnancy, diabetes mellitus, chronic renal failure, or hepatic disorders. Onset or worsening of the itching in winter would suggest xerosis. The presence of itching in family members or a household pet raises concern that the cause is an infection from a scabies or a nonscabies mite. Pruritus during or after bathing is characteristic of aquatic pruritus. Exposure to chemicals, new soaps, or detergents could cause allergic or irritant dermatitis. The review of systems often reveals other medical disorders that can be associated with pruritus (section
I.C.).
Physical examination
The physical examination includes a thorough examination of the skin in adequate lighting. Direct special attention to skin areas not easily observed or reached by the patient. Such areas may reveal a primary skin disorder or evidence of a systemic disease because some disorders present in particular areas. For example, scabies involves the interdigital webs, volar wrists, and genitalia, whereas atopic dermatitis occurs in the antecubital or popliteal fossae. Pityriasis rosea typically has a “herald patch” on the trunk. Fungal infections tend to occur in warm, dark, moist body surfaces (e.g., genitalia, feet, and inguinal folds).
Be able to recognize the classic signs of common skin disorders. Dematographism and wheals typically indicate uticaria (hives) (Chapter 13.7). Flat-topped polygonal papules with delicate white lines (“Wickham’s straiae”) are characteristic of lichen planus. Silver plaques on an erythematous base with a positive Auspitz sign (punctuate bleeding of the scale after blunt scraping) are characteristic of psoriasis. The application of lateral pressure on superficial, crusting lesions resulting in dislodging the epidermis, referred to as Nikolsky’s sign, indicates pemphigus foliaceus. The differential diagnosis of lymphadenopathy includes mycosis fungoides (Chapter 15.1). Pustular or lesions over hair follicles is a sign of folliculitis. Pay attention to new unscratched lesions because chronically excoriated skin from any cause has similar secondary changes. If lesions are present in unreachable areas, a systemic disease should be considered. In addition to the skin, examine other organ systems for organomegaly, lymphadenopathy, goiter, pregnancy, and signs of anemia or psychiatric disorders.
Diagnostic tests
If the history and physical examination do not reveal the diagnosis, certain tests can be helpful. For primary skin disorders the testing should include a wet preparation, the addition of potassium hydroxide (KOH), microscopic examination of scrapings, and as a last resort, skin biopsy. If a systemic disorder is suspected, include the following in the evaluation: a complete blood count with differential; tests for liver, renal, and thyroid function; stool for occult blood; human immunodeficiency (HIV) screen; serologic test for syphilis; and a chest radiograph. If the history and physical examination suggest other systemic diagnoses, additional recommended tests to consider include urinalysis, serum iron studies, stool for ova and parasites, serum glucose, and serum electrophoresis.
Diagnostic assessment
The diagnostic approach should initially be limited to the history and physical examination because most patients have a primary skin disorder (section I.A., I.B.). If the diagnosis is still unclear, 2 weeks of empirical treatment for the most common cause of pruritus (xerosis) is recommended. This includes less-frequent baths, use of lukewarm water and a mild soap, “pat” drying after a bath, immediate application of a lubricant, and avoidance of irritating fabrics (e.g., wool) (5). Further diagnostic tests for systemic disorder can be considered to rule out the more obscure diagnoses listed above. Because malignancy can present several years after pruritus, follow-up is important. Sometimes, no cause is found. Remember, a diagnosis of psychogenic pruritis is a diagnosis of exclusion. The relationship between the psyche and organic disease is unclear. Depression, anxiety, and other psychiatric disorders can be secondary instead of the primary illness. It is important to follow up with appropriate psychiatric or dermatologic consultation as needed.
References
1. Greco PJ, Ende J. Pruritus: a practical approach. J Gen Intern Med 1992;7:172–181.
2. Leshaw SM. Itching in active patients. Phy and Sports Med 1998;26(1):47–53.
3. Beacham BE. Common dermatoses in the elderly. Am Fam Physician 1993;47(6):
1445–1450.
4. Lober CW. Should the patient with generalized pruritus be evaluated for malignancy? [Editorial]. J Am Acad Dermatol 1988;2(Part 1):350–352.
5. Phillips WG. Pruritus. What to do when the itching won’t stop. Postgrad Med 1992;
92(7):34–53.
Book Source Details
- Book Title: The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter
- Author(s): Robert B. Taylor (editor)
- Year of Publication: 2000
- Copyright Details: The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter, Copyright © 2000 Lippincott Williams & Wilkins.
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Copyright Details: The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter, Copyright © 2008 Williams & Wilkins.
More About Causes of Ear itching
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