Segmental lichen aureus subsequent to interdigital tinea pedis: A rare clinical appearance of “id”-reaction?

A 59-year-old male visited our department, complaining of red itchy papules on his right lower leg. Initially, the papules appeared on the dorsum of his right foot, and spread upwards to the shin. He had no infectious symptoms, such as throat pain and fever, prior to the development of the dermatosis. Physical examination revealed that a number of reddish papules and erythematous lesions with slight scales were distributed along Blaschko’s lines (Fig. 1a and b). Moreover, there were scaly erythema and vesicles between the third and fourth toes (Fig. 1c), and a potassium hydroxide preparation test detected a number of fungi (Fig. 1d). Unfortunately, a mycological culture was not carried out. He had not been aware of his tinea pedis. A biopsy specimen taken from the dorsum of the foot showed parakeratosis, individual cell keratinization, spongiosis, and liquefaction degeneration in the epidermis. Furthermore, red blood cell extravasation, hemosiderin deposition, and perivascular inflammatory cell infiltrates, mainly composed of lymphocytes, were observed in the upper dermis (Fig. 1e). Immunohistochemistry revealed a number of CD4as well as CD8-positive T-cells in the dermis, with a slight predominance of CD8positive epidermal T-cells (Fig. 1f). Other dermatitis showing linear distribution, such as inflammatory linear verrucous epidermal nevus, linear lichen striatus, and linear lichen planus were all ruled out. The patient was successfully treated with topical corticosteroid (betamethasone butyrate propionate) ointment.