Manifestations and Diagnosis of Factitious Urticaria or Dermographism
The Dermographism (dermo=skin, graphism=write, writing on skin) is a cutaneous hyperreactivity characterized for the emergence of local hives on different places of skin which are exposed to friction or to a slight pressure producing a vasoconstriction followed by a manifestation of pruritus and inflammation. Sometimes the lesions may have the aspect of a “drawing” after the pressure made by some objects, thus the name of Dermographism for this condition.
The hives can emerge in a linear way after the skin has been rubbed with a blunt and narrow object reason why the shape of the hive will depend on the trace left by such a stimulus on skin. It has been estimated that about five percent of the population is affected by this condition.
The Factitious Urticaria mainly affects to young adults; there does not seem to be a special group that can be mainly affected by this condition than others. Patients present a scattered pruritus which induces the necessity of scraping skin on the area affected, after about five or ten minutes hives of a pruriginous nature start to emerge, they are of a lineal disposition and evanescent (in general hives disappear in less than one hour after they have emerged). In general the condition can get worse in the afternoon, and sometimes the lesions can be exacerbated with a hot water bath, emotions, exercise, or cold.
Physical exploration can be helpful to detect the presence of hives with distribution in areas of scratching or friction with clothes (belts, straps of bras, elastics of socks and underwear among others). Positive Dermographism can be detected through the scratching of the skin of the back (this test can be done with the help of a blunt object like a pen or a tongue depressor).
The condition falls back spontaneously in a period of time that can be of two months or ten years with an average lasting of five years. Some cases of Dermographism can be triggered by viral infections, antibiotic therapies, or emotional disorders although in most of the cases the real cause is a little bit difficult to identify.
Differential diagnosis for Dermographism or Factitious Urticaria
There is no laboratory exam that can exclude or reaffirm by itself the presence of Dermographism or Factitious Urticaria. In most of the cases the diagnosis can be confirmed by rubbing the skin with a firm dull object. The differential diagnosis of Factitious Urticaria must be done with other processes which are developed with Dermographism such as:
- Immediate simple Dermographism
- Secondary Dermographism to an acute urticaria (which spontaneously disappears after just a few days or months)
- Secondary Dermographism to a chronic urticaria (the condition appears in association to chronic urticaria and disappears along chronic urticaria)
- Dermographism associated to cholinergic urticaria (it is characterized because after the scratching appears an erythematous band but with very small hives)
- Secondary Dermographism to urticaria pigmentosa
- Late Dermographism, which appears few minutes after scratching.