The effect of anti-interleukin (IL)-4/-13 treatment, dupilumab, on allergic diseases and the resulting various unexpected phenomena have been reported in the literature. The clinical features of mycosis fungoides (MF) with multiple erythematous lesions are similar to those of atopic dermatitis (AD). Thus, anti-IL-4/-13 therapy may be erroneously administered to patients with MF with features similar to those of AD. This report is the first to describe a case of MF diagnosed after administration of dupilumab for AD.
CASE REPORTA 58-year-old man had had AD since early childhood. Although remission had occurred in adolescence, eczema had appeared on his trunk and limbs at the age of 47 years. He presented to a dermatologist and was administered topical corticosteroid ointment, betamethasone butyrate propionate, based on the diagnosis of recurrent AD. In 2013 the patient was referred to our university for treatment of a carcinoma of the maxillary sinus using chemoradiotherapy. Treatment was successful. Subsequently, the patient continued treatment for AD in our department. The cutaneous eruption was somewhat controlled by topical treatments; however, at times he experienced intense itching ( Fig. 1). He reported a history of allergic rhinitis, conjunctivitis and asthma. Given the severity of his AD, treatment with dupilumab 600 mg, subcutaneously was initiated on the first day, followed by 300 mg every 2 weeks in 2018. Serum examination prior to administration revealed elevated levels of thymus-and activation-regulated chemokine (TARC, 4,634 pg/ ml; normal range: < 450 pg/ml), IgE (1,280 IU/ml; normal range: < 250 IU/ml), and lactate dehydrogenase (LDH, 269 U/l; normal range: 124-224 U/l). The eosinophil count was within normal limits. The Eczema Area and Severity Index (EASI) was 34.4, while the Dermatology Life Quality Index (DLQI) was 8. During treatment with dupilumab, the faint erythematous lesions on the face and trunk became more obvious, despite continuous application of the topical steroid (Fig. 2). After 1 month, the EASI and DLQI were slightly decreased (29 and 6, respectively); however, there was no improvement in pruritic symptoms. Laboratory tests revealed that TARC, IgE, and LDH levels were 3,948 pg/ml, 924 IU/ml, and 287 U/l, respectively. Owing to exacerbation of the erythematous lesions, skin biopsy of the erythematous macule on the trunk was performed. Histopathology showed band-like atypical lymphocytic infiltration into the dermis. Atypical epidermotropic lymphocytes without spongiosis were observed in the epidermis, which formed Pautrier's microabscess (Fig. 3). Fig. 1. (a) Erythematous lesions on the face. (b) Poikiloderma lesions accompanied by papules and nodules on the back. Written permission from the patient is given to publish these photos. Fig. 2. (a) Face and (b) back after 1 month of treatment with dupilumab.Written permission from the patient is given to publish these photos. Fig. 3. Histopathology of the biopsy specimen from the erythematous lesion on the chest shows lymphocytic infi...