Rash at the Site of a Tattoo

The development of numerous sarcoidal lesions in tattooed areas is a classic example of an isomorphic response, or Koebner phenomenon (i.e., the appearance of identical lesions at sites of previous trauma).1 The Koebner phenomenon may occur in a variety of other cutaneous diseases, including psoriasis, vitiligo, and lichen planus.2 Studies have suggested that increases in proinflammatory cytokines, such as tumor necrosis factor α and interleukin-1, after traumatic insult play a role in the Koebner phenomenon.3 First-line therapy for cutaneous sarcoidosis is mid-to high-potency topical corticosteroids. [...]allergic contact dermatitis from poison ivy often exhibits linearly distributed vesicles that correspond to the sites of contact with the plant leaves. Histologic evaluation reveals granulomas with pigment-laden macrophages.1 Summary Table Condition Characteristics Contact dermatitis Exudative, extremely pruritic papules or plaques in a linear or geometric-appearing distribution; histologic examination shows epidermal spongiosis Cutaneous sarcoidosis Lesions typically appear as flesh-colored papules; may demonstrate koebnerization; histologic examination demonstrates “naked granulomas” Discoid lupus erythematosus Pink to red papules and plaques that become hyperpigmented or hypopigmented and atrophy; tends to affect the face, scalp, and ears; histologic examination demonstrates atrophy with an interface dermatitis involving the basal layer of the epidermis Tattoo granuloma Lesions occurring only at the site of a tattoo; histologic examination demonstrates granulomas with pigment-laden macrophages Address correspondence to Wei Teresa Hsu, MD, PhD, at wei.hsu@drexelmed.edu.