IMAGE: BENJAMIN BARANKIN, MD
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A 41-year-old white man presents with a 6-month history of a generalized pruritic erythematous eruption that comes and goes
and that spares the face, palms, soles, genitals, and scalp. He notes that the rash is worse with hot showers and exercise
and that tight clothes are bothersome.
What is your diagnosis?
How would you treat his condition?
Please go to the next page for the discussion.
Dermographism (or dermatographism)
Dermographism (literally, "writing on the skin") is characterized by an exaggerated whealing response to physical pressure
or trauma. The wheals are evanescent and edematous elevations of various sizes that may be discrete but may also coalesce.
There exists both an immediate and a delayed dermographism. The immediate response is subdivided into simple, the exaggerated physical response noted in 5% of normal people, and symptomatic, which manifests itself as linear wheals at sites of scratching and friction (such as the collar). The latter type occurs
in young adults, is worse in the evenings, and usually resolves within 2 hours. Delayed dermographism is characterized by
wheals appearing at least 30 minutes after stroking.
The general course of dermographism is unpredictable, but there is a gradual tendency to improvement over time. This condition
can be either symptomatic or asymptomatic, and most people affected with it are otherwise healthy. There is no gender or racial
variance with dermographism, and it can occur at any age.
Clinically, a whealing response usually develops within 5 minutes of firmly stroking the skin, and it can persist for up to
30 minutes. In some patients, the itching is much more severe than the whealing and often worse at night. Dermographism is
aggravated by hot baths, scratching, pressure or friction from clothing or towels, exercise, and stress. Pruritus and whealing
can affect all body surfaces, although the scalp and genitalia are rarely involved. There is no association of dermographism
with systemic disease, food allergies, atopy, or autoimmunity. The differential diagnosis includes mastocytosis, chronic urticaria,
urticarial vasculitis, urticarial bullous pemphigoid, and urticarial drug reactions.
Lab investigation and skin biopsy are rarely beneficial. A clinical history and invoking of a wheal response are diagnostic.
The clinician should apply moderate pressure to gently scratch the skin, with the back considered the best site for this test.
Allow at least 30 minutes for the response to develop, although in most patients it will develop within a few minutes.
Treatment
Recognizing the problem and avoiding precipitating physical stimuli are quite beneficial. Cooling lotions (such as calamine
lotion [eg, Caladryl]) can provide modest relief. Nonsedating second- and third-generation antihistamines (eg, cetirizine
[Zyrtec], loratadine,* or desloratadine [Clarinex]) are the medications of choice, and trials of various antihistamines and
combinations to find the best individualized treatment may be required. Sedating antihistamines such as diphenhydramine (Benadryl)
or hydroxyzine (Vistaril) can be used at night if needed. Some patients may benefit modestly by the addition of an H2-receptor blocker (such as cimetidine [Tagamet] or ranitidine [Zantac]) if they are not responding to an H2-receptor blocker alone. Finally, the tricyclic antidepressant doxepin (Sinequan), a potent H- and H2-receptor blocker, can be tried in combination with antihistamines at low dosages (10-50 mg qhs) in refractory cases.* Systemic
corticosteroids are not helpful, and phototherapy is inconclusive or, at most, modestly beneficial.
Treatment often continues for months and up to several years. The side effects of antihistamines and doxepin, especially drowsiness,
should be discussed.
*Unlabeled use.
BENJAMIN BARANKIN, MD, Senior Dermatology Resident, University Dermatology Centre, University of Alberta, Edmonton, Canada.
RONALD G. WHEELAND, MD, Contributing editor, Professor and Chief, Section of Dermatology, Department of Medicine,University of Arizona Health Sciences Center, Tucson;
and member,Patient Care Subspecialist Advisory Board.
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