Dermatographism

Etiology

The exact cause of dermatographism is unknown. However, the release of histamine from mast cells is thought to play a role.[2] Dermatographism has been seen in people with diabetes, hyperthyroidism, hypothyroidism, menopause, pregnancy, or medication-related conditions.

Epidemiology

Dermatographism is the most common type of urticaria, frequently presenting in young adults, with the peak incidence in the second and third decades. There has not been shown a relationship between race and dermatographism. One study of pediatric patients showed a female predominance.[3] One report cited a case of familial dermatographism.[4] Hypereosinophilic syndrome is associated with atopic children and increases dermatographism; these are associated with atopic children and an increased number of eosinophils in the blood. One-third of patients who experience traumatic life events, along with psychological co-morbidities, experience dermatographism.[5] 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 of systemic mastocytosis.[6]

Pathophysiology

No concluding mechanism explains why dermatographism occurs. Mechanical trauma activates vasoactive mediators released from mast cells secondary to antigen interaction with the bound IgE. This is thought to cause an exaggerated biological response known as the "triple response of Lewis." 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, which subsides in under 10 minutes. Mediators such as histamine, leukotrienes, bradykinin, heparin, kallikrein, and peptides such as substance P are all considered to play a role in this process.

Histopathology

The histopathology of dermatographism demonstrates dermal edema with few perivascular mononuclear cells, similar to acute urticaria histology.

History and Physical

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 persists for about 15 to 30 minutes. The deeper the edema into the dermis, the larger the wheal appears. In symptomatic dermatographism, pruritus accompanies the wheal. The pruritus worsens at night (thought to be related to the pressure of the bedding and sheets contacting the skin) and friction to the area from external stimuli, heat, stress, emotion, and exercise. Dermatographism most commonly involves the trunk extremities and other body surfaces. The least common areas reported are the scalp and genital area; however, the literature has correlated symptomatic dermatographism with dyspareunia and vulvodynia.[7]

There are several rare subtypes of dermatographism:

• 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 the initial injury that persists up to 48 hours)
• Cold-precipitated
• Exercise-induced
• Familial

Treatment / Management

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 symptomatic patients. Choice therapy includes treatment with H1 antihistamines such as cetirizine or loratadine. H2 antihistamines can be combined for more complete therapy if H1 blockers are insufficient to control the pruritus. Hydroxyzine, a sedating antihistamine, is a valid option and can be taken before sleep. Omalizumab is under consideration in research trials focusing on treating dermatographism with 72% efficacy on 150 mg and 58% efficacy on 300 mg. Notably, patients' Dermatology Life Quality Index scale improved by at least 4 points, showing a statistically significant clinical difference.[8] Light therapy has shown some efficacy in treating 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.[9](A1)

Differential Diagnosis

If dermatographism is the leading differential, false dermatographism must be ruled out, a condition that presents clinically similar to dermatographism but has a different underlying mechanism. False dermographism has several different forms, including white, black, and yellow. White dermatographism is secondary to allergic contact dermatitis and is prevalent in atopic individuals. Black dermatographism occurs after contact with metallic objects. Yellow dermatographism is due to bile deposits in the skin. Another condition that presents similarly to symptomatic dermatographism is latex allergy. This commonly is seen on the hands and genital region and can often be related to a history of physically contacting latex in gloves, rubber bands, balloons, toys, or contraceptive use.[10] Mastocytosis, a disorder caused by an increase in the number of mast cells, can also present with pruritic red-brown pigmented lesions. Mastocytosis can be cutaneous or systemic, depending on what area is infiltrated with mast cells. One sign of mastocytosis is called the "Darier sign," which is swelling, pruritus, and erythema in response to pressure applied to the skin. 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. Urticaria pigmentosa is the most common cutaneous mastocytosis in children and is rare and benign.[11]

Prognosis

Dermatographism is a benign condition. In a minority of cases, pruritus can accompany the condition. Compared to the other chronic urticarias, symptomatic dermatographism displays the most expedited clearance of the condition after 5 years (36%) and 10 years (51%).[12]

Complications

Dermatographism has no direct complications. However, if the patient uses sedating antihistamines for treatment, they may need to exercise caution before engaging in certain activities such as driving or operating machinery.