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Indian Journal of Dermatology, Venereology and Leprology, Vol. 74, No. 2, March-April, 2008, pp. 177-179 Resident's Page Dermatographism Bhute Dipti, Doshi Bhavana, Pande Sushil, Mahajan Sunanda, Kharkar Vidya Department of Dermatology, Seth G. S. Medical College and KEM Hospital, Mumbai Code Number: dv08075 Introduction Dermatographism also called as skin writing, dermographism or dermatographic urticaria is an enigma for dermatologists and immunologists alike. Although simpler to elicit, its clinical relevance or significance is yet to be fully known. When normal skin is stroked with a dull object, it becomes raised and inflamed to assume the shape of the stroke. [1] The response consists of local erythema followed by edema and a surrounding flare reaction. Exaggeration of this response is known as dermatographism. Dermatographism can appear in persons of any age but is more common in young adults. Peak incidence is in the second and third decades of life. Symptoms of itching, rash and whealing are induced by scratching, stroking, tight or abrasive clothing or other personal wear. Rubbing, minor pressure or any form of physical stress to the skin may initiate lesions. Scalp, genitalia, mucocutaneous junctions and mucosae are involved less frequently. How to Elicit Dermatographism The diagnosis is usually made by observing the clinical response after using moderate pressure to stroke or gently scratch the skin [Figure - 1]. The site of elicitation of dermatographism is important as areas protected from regular pressure and environmental influences are more reactive than others. For this reason, dermatographism is elicited more markedly over the trunk as compared to the limbs. As the pressure of a stroke has inter-individual and intra-individual variations, a calibrated instrument known as a dermographometer can be used for applying uniform pressure over the skin. It has a spring-loaded stylus that applies graded and reproducible pressure (of 3600 g/cm 2 ) over the skin and then records skin responses. Although, it can also be used in children effectively, its current use is limited to research settings. Pathophysiology of Dermatographism Firm stroking of the skin produces an initial red line (capillary dilatation) followed by an axon-reflex flare with broadening erythema (arteriolar dilatation) and the formation of a linear wheal (transudation of fluid/edema). This is termed as the triple response of Lewis. An exaggerated form of this response is known as dermatographism. Unfortunately, the so-called exaggeration is highly subjective and thus not enough to distinguish between dermatographism and the triple response of Lewis with precision and surety. The time needed for the response to occur after stroking may help to some extent. Dermatographism usually develops within five minutes of stroking the skin and persists for 15-30 min in contrast to the normal triple response of Lewis that subsides in less than 5-10 min. A short refractory period after clearance of the wheal has been reported in dermatographism. [2] The exact mechanism of dermatographism remains uncertain but according to many, it is likely to be caused by ′mechanico-immunological′ stimulation of mast cells that release histamine. Mechanical trauma is thought to release an antigen that interacts with IgE-sensitized mast cells, which further release inflammatory mediators like histamine into the tissues. This causes small blood vessels to leak, allowing fluid to accumulate in the skin. Other mediators possibly involved are leukotrienes, heparin, bradykinin, kallikrein and peptides such as substance P. Thus, the proposed mechanism simulates a type I hypersensitivity reaction with the difference of being triggered by mechanical trauma and not by external immunologic stimuli. This hypothesis is supported by successful passive transfer of dermatographism to normal subjects by serum or IgE and its association with urticaria syndromes. [3] Histopathology of dermatographism shows dermal edema with a few perivascular mononuclear cells similar to acute urticaria. Mixed interstitial infiltrate comprising neutrophils, eosinophils and lymphocytes as seen in late lesions are not seen in dermatographism. Types of Dermatographism The phenomenon of dermatographism has the following morphological features, the unifying character of which is the appearance of urticarial lesions following stroking of the skin.
Differential Diagnosis Symptomatic dermatographism has to be differentiated from Darier′s sign seen in urticaria pigmentosa and systemic mastocytosis in which the actual number of skin mast cells is increased due to mast cell hyperplasia. However, symptomatic dermatographism is also observed in mastocytosis after stroking uninvolved skin. Whether this phenomenon is a positive, nonlesional Darier sign or dermatographism is not clear as yet. [8] Symptomatic dermatographism appears at the site of strokes or pressure while urticarial wheals appear de novo . Both are pruritic once apparent. Urticarial wheals are usually well-demarcated, round or annular plaques while dermatographism in a given patient assumes the shapes of the strokes/pressure. Dermatographism disappears within 30 min (except in delayed pressure urticaria) whereas urticarial wheals last longer and disappear within 24 h.Significance Dermatographism is seen in 4-5% of the normal population. [9] Its prevalence in chronic idiopathic urticaria is reported to be 22% [3] but a few authors believe that dermatographism is not increased in chronic idiopathic urticaria. [6] In clinical practice, it is essential to differentiate episodes of dermatographism from chronic urticaria and the search for exogenous or endogenous antigens by intradermal tests or autologous serum skin test respectively, is probably unwarranted. Dermatographism is also called as mechanical urticaria. In that sense, it is a type of physical urticaria. However, it has been reported in association with chronic idiopathic urticaria (22%), cholinergic urticaria, hypereosinophilic syndrome, [10] drug-induced urticaria, [11] reactive polyarthritis with Helicobacter pylori [12] and endocrinopathies like hyperthyroidism, hypothyroidism, diabetes mellitus, [13] etc. A single case of familial dermographism probably inherited as an autosomal dominant trait has been reported. [9] Cutaneous manifestations of dermatographism may be occasionally associated with mucosal symptoms. Cases of bronchial hyperreactivity [14] and mucosal affection [15] have been reported. Oral discomfort resulted in difficultly in maintaining oral hygiene in the patient. [15] False Dermatographism Apart from classical dermatographism and its types, several other types of cutaneous responses associated with or without stroking of the skin entities have been described as dermatographism. These are as follows:
Treatment Avoidance of precipitating physical stimuli, reduction of stress and anxiety are important factors. H1-antihistamines are the drugs of choice. However, combining H1 and H2 antihistamines has sometimes resulted in better control of the wheals. Other treatment options like NB-UVB therapy and psovalent + UVA (PUVA) therapy have been used with limited success.References
Copyright 2008 - Indian Journal of Dermatology, Venereology and Leprology The following images related to this document are available:Photo images[dv08075f1.jpg] |
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