[Adult blaschkitis (lichen striatus) successfully treated with topical tacrolimus].

Lichen striatus is a self-limiting inflammatory dermatosis that is characteristically distributed along the Blaschko lines. It is usually seen in children although cases, with different histopathological features, have been reported in adults. In view of the characteristic clinical features of the disease in adults—with its papulovesicular aspect—it is known as blaschkitis. Subsequently, different attempts have been made to define these conditions. A 70-year-old man with a family and personal history of atopy attended the clinic for a pruriginous multilinear papulovesicular eruption on the trunk and right leg that had appeared 6 months earlier. Treatment over the preceding month with methylprednisolone aceponate applied as a 0.1% cream had led to no improvement. The multilinear eruption took the form of a papulovesicular eruption that followed the Blaschko lines on one side of the body; it was more intense on the leg (Figures 1A, C, and E). Histopathological study showed a lichenoid inflammatory infiltrate that extended to the mid-dermis (Figure 2A). The composition of this infiltrate was polymorphous, with the presence of lymphocytes, plasma cells, histiocytes, and a notable presence of eosinophils. The epidermis showed irregular epidermal hyperplasia, with compact hypergranulosis and hyperkeratosis but no parakeratosis. Limited spongiosis was present. No transepidermal migration of inflammatory cells was observed. In addition, clefts were observed between the dermis and epidermis, along with basal apoptotic keratinocytes and pigmentary incontinence (Figure 2B). Perieccrine thickening of the deep dermis was observed. Once lichen striatus had been diagnosed, the patient was instructed to apply an ointment containing 0.1% tacrolimus twice a day for the first month to the lesions on the trunk, which disappeared, and to the legs in the second month, with the same results (Figures 1B, D, and F). After 6 months of follow-up, no recurrences had been reported. Lichen striatus is an uncommon, self-limiting, linear dermatosis, which usually affects children and is rare in adults. It is distributed unilaterally, although some cases of bilateral distribution have been reported.1 At present, given its distribution pattern, it is considered a somatic mosaicism. The cause is unknown, although an immune mechanism has been proposed whereby killer T cells eliminate keratinocytes with a postzygotic mutation.2 Lichen striatus is often associated with atopic dermatitis, and it has also been suggested that the altered immune status of these patients might act as a predisposing factor to trigger the process.2 Tacrolimus, an inhibitor of inflammatory cytokine production by T cells, has been shown to be useful in the treatment of isolated cases of lichen striatus.3-5 In our case, as the patient was treated in 2 different areas at 2 different times and a rapid response was obtained, the resolution of clinical symptoms can probably be attributed to topical tacrolimus and not the natural course of the disease. Adult Blaschkitis (Lichen Striatus) Successfully Treated With Topical Tacrolimus