The Diagnosis: Isomorphic Psoriasis
Tattooing has become an increasingly popular trend among young people. Currently, there are no guidelines in the United States regulating the production of tattoo ink and pigments.1 Henna tattooing, a form of temporary skin painting, also has risks of allergic contact dermatitis from paraphenylenediamine dye.2 Complications following tattoo application include an allergic contact dermatitis to tattoo pigments, infection, granulomatous and lichenoid reactions, and skin disease localized to the tattooed area.3
Localized dermatosis arising in a traumatized area, or the Koebner phenomenon, was first described by Heinrich Koebner in 1877.4 He described the formation of psoriasiform lesions at the site of cutaneous trauma.5 These isomorphic lesions can occur in 25% of patients with psoriasis after trauma to the skin such as tattooing.6 Other dermatologic diseases that can present as an isomorphic response to tattooing include lichen planus, Darier disease, vitiligo, and autoimmune bullous disease.3,5,6
Various causes of trauma such as burns, insect bites, physical trauma, and needle trauma have been shown to produce new psoriatic lesions.6 The time period from trauma to formation of psoriasiform lesions usually ranges from 10 to 20 days; however, an initial reaction can occur as early as 3 days or as long as 2 years after trauma.4 Although the pathophysiology of the isomorphic response is not well known, it has been shown that nerve growth factor has a role. Raychaudhuri et al7 demonstrated the upregulation of nerve growth factor in the development of a psoriatic lesion, influencing keratinocyte proliferation, angiogenesis, and T-cell activation.
Physical trauma such as tattooing has been shown to cause an isomorphic response in psoriasis. We describe a case of isomorphic psoriasis in a patient after tattoo application. Our patient had a several-month history of well-controlled psoriasis prior to obtaining the new tattoo. Several days after receiving the tattoo, the patient reported an increase in psoriatic lesions, including at the site of the tattoo. The trauma causing the isomorphic response could have been either a response to the tattoo pigment or needle injury to the skin.6
Psoriasis and isomorphic lesions can be treated with topical corticosteroids as well as systemic and biologic agents. Our patient was treated with triamcinolone cream with good response.8