To the Editor:
Tocilizumab (TCZ) is a humanized monoclonal antibody directed against the interleukin 6 (IL-6) receptor, approved in the treatment of rheumatoid arthritis (RA), with potential use in other inflammatory diseases1. We describe a case of psoriasis onset during TCZ treatment in a patient with RA.
A white woman, born in 1955, for 20 years had erosive RA, negative for anticitrullinated protein antibodies. Her condition did not respond to several disease-modifying antirheumatic drugs (hydroxychloroquine, methotrexate, leflunomide) or to 2 tumor necrosis factor-α (TNF-α) blockers (etanercept, adalimumab). TCZ was then tried: 8 mg/kg/infusion in monotherapy, and later with 5 mg/day prednisone. After the third infusion (9 weeks of exposure to TCZ), she developed for the first time a psoriasis eruption on the left leg (Figure 1) and left elbow. The diagnosis was confirmed by a dermatologist and treated topically, without discontinuing TCZ. At the onset of psoriasis lesions, the RA responded to the treatment (28-joint Disease Activity Score 5.12 to 3.49; erythrocyte sedimentation rate 15 mm/h; C-reactive protein 1.5 mg/l).
Erythematous squamous lesions of the leg.
This case may illustrate a new kind of unexpected event in a patient whose arthritis is controlled by TCZ. Similar cases have been reported2, with exacerbation of preexisting psoriasis within 2 weeks after the first infusion of TCZ. Ogata, et al3 reported 2 cases of psoriatic arthritis treated with TCZ over 6 months without improvement in arthritis and skin lesions. Conversely, Brulhart, et al4 described a complete resolution of skin psoriasis in a patient treated with TCZ for severe ankylosing spondylitis associated with Crohn’s disease.
Increased production of IL-6 and upregulation of transcription factor STAT3 induced by IL-6 have been shown in psoriasis5, and plasma IL-6 levels seem to reflect psoriasis activity and treatment response6. Under these circumstances, onset or exacerbation of psoriasis is unexpected.
This kind of new onset or reactivation of psoriasis under biologic therapy for rheumatologic indications has been reported with TNF blockers7, rituximab8, and abatacept9.
In the few cases reported, psoriasis with TCZ is mild and may be controlled with topical treatment, with continuation of IL-6 blockade if effective on joint and general disease symptoms.
