The differential diagnosis and workup of pruritus: Determining the cause of pruritus may be a straightforward clinical exercise when a rash is present. But what about when it isn't?

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Author: Jennifer Winter
Date: Feb. 2002
From: JAAPA-Journal of the American Academy of Physicians Assistants(Vol. 15, Issue 2)
Publisher: Haymarket Media, Inc.
Document Type: Article
Length: 3,052 words

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Pruritus can frustrate the patient and challenge the provider, particularly when the cause is elusive and symptoms are persistent. The history and physical exam usually offer significant clues, but referral to a dermatology specialist may be warranted when the cause is hard to pin down.


A focused history should elicit onset, exacerbations, and location of the pruritus. Ask the patient to describe any associated sensation, such as a sting, itch, or burn, and ask what treatments have been used--including moisturizers or prescription, OTC, or alternative therapies--and if symptoms have responded. Determine whether certain activities appear to affect the condition, and ask what appears to exacerbate or relieve symptoms. If a rash is present, have the patient describe its early appearance and whether it has changed. Ask the patient, "What do you suspect is the cause?"

In addition to asking about agents used to treat the pruritus, inquire about other prescription, OTC, and alternative products, as well as other remedies used that would suggest a drug allergy and possible reaction. During the medical history, inquire about the personal and family history of atopy (allergies, asthma, and eczema), psoriasis, and dry skin. Pay close attention to the patient's responses to questions about renal and hepatic conditions, which may provide a clue to a systemic cause of the pruritus. Ask about exposures to irritants such as poison ivy, scabies, a virus, or chemicals; to the sun; and to anybody who has pruritus. In some cases, just a known exposure to scabies can cause pruritus in the absence of infestation. A thorough history and exam may reassure the person enough to resolve the symptoms.

Describing the lesion

Note the location, quality or morphology, shape, distribution, and color of the lesion. Is it located in a skin fold or extensor surface? Is it symmetric, accessible to scratching, and on skin regularly exposed to the sun? Note the quality--is it nummular, nodular, macular, moist, dry, targetoid, vesicular, follicular, eczematous, scaling, urticarial, excoriated, or a plaque or papule? Is it round, linear, or oval? Is distribution widespread or localized? Is the lesion erythematous, violaceous, hypopigmented, hyperpigmented, dusky, or bright (see "Derm terms: A primary care review," page 36)?

Differential diagnosis

In many cases a diagnosis may be made from the history and clinical appearance alone, although laboratory tests may be required in others. The following dermatologic conditions are closely associated with pruritus.

* Atopic dermatitis Also known as eczema, atopic dermatitis is associated with skin that is easily irritated. Family history of atopy or eczema may be noted. In infants, atopic dermatitis typically manifests as dry, red, itchy skin, commonly on the cheeks and in the diaper area (see Figure 1, page 36). In children older than 2 years, the condition commonly appears as erythema and scaling in the antecubital and popliteal fossae. Rash is less common in adults, although the skin is easily irritated--especially on the hands of those in frequent contact with water. Staphylococcus aureus colonization is common; in these circumstances the atopic dermatitis may...

Source Citation

Source Citation
Winter, Jennifer. "The differential diagnosis and workup of pruritus: Determining the cause of pruritus may be a straightforward clinical exercise when a rash is present. But what about when it isn't?" JAAPA-Journal of the American Academy of Physicians Assistants, vol. 15, no. 2, 2002, p. 35+. Accessed 21 Jan. 2021.

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