Development of Sarcoidosis Subsequent to Temporary Corticosteroid Treatment in a Patient With Rheumatoid Arthritis

A 69‐year‐old Japanese woman was diagnosed with rheumatoid arthritis and treated with tacrolimus because of worsening symptoms of arthritis. Four months after tacrolimus initiation, corticosteroids were administered. Arthritis improved after 4 months of corticosteroid administration, and the corticosteroid treatment was terminated. However, 2 months after corticosteroid treatment cessation, the patient developed mediastinal and hilar lymph node swelling, subcutaneous node swelling, uveitis, and elevated serum sarcoidosis‐associated markers. Consequently, the patient was diagnosed with sarcoidosis, characterised by non‐serodermal epithelial granuloma cells with positive staining for anti‐ Propionibacterium acnes antibody. Notably, all symptoms improved without systemic steroid administration. Corticosteroids and tacrolimus can affect CD4+ lymphocyte function and number; in the present case, given the use of temporary corticosteroids, they may have caused immune reconstitution inflammatory syndrome‐like pathogenesis, which can result in transient sarcoidosis.