Dermatographism, also known as Dermographism urticaria, or urticaria factitia, is an urticarial eruption upon rough downward motion or scratching of the skin. The literal meaning is, "to write on the skin." This writing on the skin produces a linear wheal in the shape of the downward external force that was applied.
Dermatographism, the most common type of physical urticaria, is thought to occur in approximately 2% to 5% of the population. Inducible urticaria is the preferred term for physical urticaria according to the 2018 International guideline. Symptomatic dermatographism, a small subset of the condition state, describes the patients that have associated pruritus along with the erythematous wheals.
Dermatographism is due to an unknown cause. Current hypotheses are described in pathophysiology.
Among the different types of urticaria, dermatographism is the most common. The condition frequently presents in young adults with the peak incidence in the second and third decades. There is no gender predilection, yet one study of pediatric patients showed a female predominance. Further, there is no recognized racial predilection for dermatographism. However, one report cited a case of familial dermatographism.
Furthermore, a majority of patients with hypereosinophilic syndrome have dermatographism; these are associated with atopic children. One-third of patients that experience traumatic life events along with psychological co-morbidities experience dermatographism. Furthermore, stressful events like pregnancy (commonly in the second trimester) and the onset of menopause have seen a higher incidence of the condition. Behcet disease, a condition marked by oral and genital ulcers, is another disease where dermatographism is a common integumentary finding.
Symptomatic dermatographism is thought to be generally idiopathic, but various explanations have been considered. The higher consensus revolves around Helicobacter pylori, antibiotics such as penicillin, bites, or scabies as the more common presentations to suggest this correlation. Lastly, congenital symptomatic dermatographism is the presenting sign in systemic mastocytosis.
No concluding mechanism explains why dermatographism occurs. However, the triple response of Lewis is an exaggeration to the entire process. Initially, the capillaries become dilated, producing a superficial erythematous phase. Next, an axon-reflex flare and communication to sensory nerve fibers cause an expansion of erythema, secondary to arteriolar dilation. Lastly, the linear wheal is formed through fluid transudation. This entire response takes, on average, up to 5 minutes after an external stimulus stroking of the skin. The wheal can persist anywhere from 15 to 30 minutes, unlike the normal triple response of Lewis that subsides in under 10 minutes.
Mechanical trauma activates vasoactive mediators released from mast cells secondary to antigen interaction to the bound IgE. This is thought to be the primary explanation for the exaggerated response of the triple response of Lewis. Furthermore, mediators such as histamine, leukotrienes, bradykinin, heparin, kallikrein, and peptides such as substance P are all considered to play a role in this process.
The histopathology of dermatographism demonstrates dermal edema with few perivascular mononuclear cells, not entirely different to acute urticaria.
Dermatographism lesions appear following mechanical trauma to the skin, most consistently stroking of the skin. A wheal forms and develops in approximately 5 to 10 minutes. The wheal will persist for about 15 to 30 minutes. The deeper the edema into the dermis, the larger the wheal will appear. In symptomatic dermatographism, pruritus accompanies the wheal. The pruritus worsens at night and with friction to the area from external stimuli, heat, stress, emotion, and exercise.
Most body surfaces are implicated with the condition, specifically the scalp and genital area accounting for the least amount of incident reporting. With this being said, symptomatic dermatographism has been correlated in the literature with dyspareunia and vulvodynia.
Subtypes of dermatographism are rare but include red dermatographism (small punctate wheals, predominantly on the trunk), follicular dermatographism (isolated urticarial papules), cholinergic dermatographism (similar to cholinergic urticaria – large erythematous line marked by punctate wheals), delayed dermatographism (tender urticarial lesion reappears 3 to 8 hours after initial injury that persists up to 48 hours), cold-precipitated/exercise-induced and familial, yet are uncommon.
Prevention and avoidance of precipitating factors such as physical stimuli and decreasing stressors are important factors in controlling dermatographism. Most patients are asymptomatic, and therapy should be restricted to patients that are symptomatic. Choice therapy includes treatment with H1 antihistamines such as cetirizine or loratadine. H2 antihistamines can be combined for a more complete therapy if H1 blockers are not sufficient to control the pruritus. Hydroxyzine, a sedating antihistamine and valid option, should be taken before sleep.
Omalizumab is under construction in research trials focusing on treating dermatographism with 72% efficacy on 150mg and 58% efficacy on 300mg. Notably, patients' Dermatology Life Quality Index (DLQI) scale improved by at least 4 points, showing a statistically significant clinical difference.
Furthermore, light therapy has shown some efficacy in the treatment of dermatographism, yet most patients relapse within 2 to 3 months of completing therapy .
Adjunctive treatment with over the counter vitamin C, 1000 mg daily, is thought to help degrade histamine and increase removal, diminishing the triple response of Lewis.
If dermatographism is the leading differential, it is imperative that false dermatographism is ruled out. The condition is similar to dermatographism but does not include urticaria. The different forms of false dermographism include white, black and yellow. White dermatographism is prevalent in atopic individuals. Black dermatographism appears black and occurs after contact with certain metallic objects. Yellow dermatographism is likely due to bile deposits in the skin.
Other diagnoses related include latex allergy, with it closely resembling symptomatic dermatographism, commonly seen on the hands and genital region. Systemic mastocytosis and urticaria pigmentosa closely resemble similar findings, both eliciting swelling, pruritus, and erythema, known as a positive Darier sign. Urticaria pigmentosa is the most common cutaneous mastocytosis in children. It is rare, harmless, and causes red-brown pigmented lesions with associated pruritus. Systemic mastocytosis is more common in adults, and symptoms are based primarily on the organ affected, such as the liver, spleen, bone marrow, or small intestine.
Dermatographism is a benign condition. In a minority of cases, pruritus can accompany the condition. In comparison to the other chronic urticarias, symptomatic dermatographism displays the most expedited clearance of the condition after 5 years (36%) and 10 years (51%).
Dermatographism can be unsettling in its laborious course without resolve. However, the condition is benign, and it is vital for patients to be aware of this. The treatment involved, antihistamines, can result in drowsiness; therefore, it is best to advise the patient to not take the medication before operating a vehicle.
Dermatographism is a benign, yet startling lesion to most patients and their parents. Thus, it is imperative to educate the patient and their parents properly on the risk factors associated with the onset of dermatographism to avoid such stressors. To properly educate, it is ideal to target the audience in a team-based approach.
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