A Case of Blaschkitis with Features of Both Lichenoid and Spongiotic Dermatitis.

Sir,

In 1990, Grosshan and Marot first described blaschkitis (BL), an acquired linear inflammatory dermatosis following Blaschko lines in an adult patient.[1] BL is a rare skin disease with many similarities to lichen striatus (LS). LS is an acquired inflammatory dermatosis that follows the Blaschko lines. LS occurs mainly in children and is rarely seen in adults. Clinically, it is presented by erythematous 1–2 mm flat-topped papules on extremities. The histopathological findings indicate mostly lichenoid dermatitis.[2]

The patient Grosshan and Marot reported was an adult presenting by multiple lines of erythematous papules and vesicles mainly located on the trunk with rapid resolution within 2 months and led them to introduce BL as a separate entity from LS. Histopathologically, BL has been characterized as a spongiotic dermatitis.[13] We present a case of BL with histological features of both lichenoid dermatitis and spongiotic dermatitis which indicates similarities to both BL and LS.

A 56-year-old woman presented with a 2-month history of papules and few plaque-type lesions on her trunk, abdomen, upper back, and neck. The lesions had linear distribution along the lines of Blaschko. Physical examination revealed multiple 3–6 mm erythematous papules involving the trunk, abdomen, and upper back in a linear pattern [Figure 1]. A biopsy from her lesions revealed parakeratosis and both features of lichenoid dermatitis and spongiotic dermatitis were present [Figure 2]. Treatment with topical steroids over 2 months showed relative resolution of the existing lesions, however new lesions developed.

Figure 1

(a) Linear eruptions following the lines of Blaschko on the trunk (b) thigh (c) and upper chest

Figure 2

(a) The histopathological findings were consistent with both lichenoid dermatitis (H and E, ×40) (b) and spongiotic dermatitis (H and E, ×100)

Whether LS and BL are separate entities or are variations of the same disease remain controversial. Keegan et al. in 2007 concluded that these two diseases are different in their clinical presentation and histopathological findings. They presented differentiating features between LS and BL which are shown in Table 1.[1] In contrast, Hofer proposed that due to lack of differentiating clinical and histological features, BL and LS may actually be the same.[4] In 2011, Müller et al. reported six patients all presenting with erythematous papules along Blaschko lines. They found no association between clinical characteristics such as age, location or associated disorders, and histological findings such as lichenoid inflammatory infiltrate or spongiosis. Finally Müller et al. proposed the theory that both LS and BL are describing the same Blaschko linear dermatoses with slightly different clinical and histological findings. They believed that these differences could be explained by the “life of lesion” phenomenon, the fact that more spongiotic dermatitis in BL and more interface alterations in LS could be due to the existence of different stages of the disease pathologically.[5]

Table 1

Differentiating features between Lichen striatus and blaschkitis

Considering the literature, the previously reported cases of BL were described mainly as spongiotic dermatitis. However, our case showed both spongiotic and lichenoid dermatitis, compatible with histopathological features of BL and LS, respectively. Our observation further supports the theory that BL and LS are describing the same disease. The unifying of these two diseases with similar clinical and histological features could be helpful for simplifying diagnosis and treatment clinically.

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Conflicts of interest

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