Tocilizumab‐induced pustular drug eruption

Dear Editor, Tocilizumab is a humanized anti-interleukin-6 (IL-6) receptor antibody, which has recently been approved for the treatment of moderate to severe rheumatoid arthritis (RA). However, since then several types of tocilizumab-related rash have been reported. A 69-year-old woman who had been suffering from RA for over 15 years was referred to our department, complaining of symptomless skin eruptions on the extremities and trunk. She had been treated with tocilizumab (400 mg) infusion once a month for 7 months, and 2 days after the seventh infusion, erythema appeared on her upper extremities, which spread to the shoulders and lower extremities. On physical examination, multiple erythema with many tense vesicles and small pustules were widely recognized on the dorsal aspects of the upper and lower extremities (Fig. 1a). Laboratory examination showed normal ranges of white blood cell counts (3200/lL) and C-reactive protein (0.03 mg/dL), whereas increased levels of eosinophil ratio (12%), positive rheumatoid factor (93 IU/mL, normal < 20), and matrix metalloproteinase-3 (MMP-3; 715 ng/mL, normal 17.3–59.7). Serological examination revealed positive anti-nuclear antibody (1 : 160, homogeneous and speckled), antiDNA antibody (8.3 IU/mL, normal < 6.0), and anti-double-stranded DNA immunoglobulin G (IgG) antibody was weakly positive (13 IU/mL). Serum titers of IgG