Case report
A 64-year-old man was referred to our Department of Dermatology with a 1-day history of annular erythema on his trunk. The patient was diagnosed with Philadelphia chromosome-positive B-ALL based on the finding of the infiltration of leukemia cells with CD79α, CD10, and terminal deoxynucleotidyl transferase (Tdt) antigens into the bone marrow 9 months previously. The patient was treated with combination chemotherapy consisting of cyclophosphamide, vincristine, doxorubicin, and dexamethasone, resulting in complete remission, followed by consolidation therapy with dasatinib. However, the recurrence of B-ALL was confirmed 5 months previously based on the detection of bcr/abl mRNA of 4,100,000 copies/μg RNA by a real-time polymerase chain reaction. Therefore, the patient was referred to our Department of Oncology/Hematology and was treated with blinatumomab (1 course of 42 days; 9 μg/day on days 1 to 7, 28 μg/day on days 8 to 28, and washout on days 29 to 42).
On day 5 in the 4th course of blinatumomab, the patient developed erythema on his trunk. On day 6, he visited our Department of Dermatology for the eruption and we noted multiple erythema with an annular appearance and ranging in size from 2 to 5 cm in diameter on his trunk (Figure 1). A histopathological examination of erythema showed that mononuclear cells with dense chromatin and mild atypia infiltrated the nucleus around the vessels and adnexa in the dermis and a few mitotic cells were present (Figure 2a and 2b). An immunohistochemical analysis revealed that infiltrating mononuclear cells were reactive to anti-CD79α, CD10, and terminal Tdt antibodies (Figure 2c, 2d, and 2e, respectively), which was compatible with the bone marrow findings observed 9 months previously. Cutaneous manifestations were diagnosed as LC due to B-ALL and disappeared on day 7 in the 4th course, leaving only pale pigmentation when treated with topical corticosteroids.