| Summary: | Background: New-onset sarcoidosis has been previously described in three case reports in patients affected by rheumatoid arthritis treated with tocilizumab (TCZ). The existence of a cause–effect mechanism between the biological treatment and the onset of the illness is still being debated. Patient concerns: A 74-year-old woman was diagnosed with giant cell arteritis (GCA). The first-line treatment with glucocorticoids; and the second-line with methotrexate and low-dose glucocorticoids were stopped due to multiple pathological vertebral fractures and insufficient biological and clinical response. The cytotoxic agent, cyclophosphamide, was then introduced and in turn stopped, because of gastrointestinal side effects. Thereafter a treatment with TCZ was begun. The patient experienced good clinical response; however, 8 months later she developed painful hyper-pigmented reddish cutaneous micronodular lesions localized to the abdomen and thorax. A cutaneous biopsy was performed, and histological analysis showed noncaseating epithelioid granulomas in the hypodermis. The diagnosis of cutaneous sarcoidosis was made. Interventions: Topical corticosteroids were administered and, as requested by the patient, TCZ was discontinued with slow but complete resolution of the skin lesions. After TCZ discontinuation however, the GCA flared and the patient’s symptoms and biological abnormalities reappeared. Thus, after a 6-month suspension, TCZ was re-administered. At 2 months later the skin lesions compatible with cutaneous sarcoidosis reappeared. Topical corticosteroids were once again prescribed and as suggested by the patient the TCZ posology was reduced. The patient’s symptoms disappeared, and the cutaneous lesions resolved. Lessons: The time elapsed from TCZ treatment start and the onset of cutaneous sarcoidosis, as well as its recurrence after TCZ suspension and rechallenge supported the diagnosis of a drug-induced reaction. To the best of our knowledge, this case report represents the first instance of cutaneous sarcoidosis most likely induced by TCZ in patients affected by GCA. In addition, our case emphasizes that although TCZ in monotherapy confirms to be an effective treatment for GCA, further immunological disorders could be unmasked, and the discussed side effect of the drug could be dose-dependent.
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