Etanercept-associated episcleritis: a pediatric case report of a paradoxical adverse reaction and review of the literature

Scleritis is an inflammation of the episcleral and scleral tissues, characterized by injection in both superficial and deep episcleral vessels. When only episcleral tissue is involved, it is referred to as episcleritis. Episcleritis is mainly idiopathic but may be secondary to an underlying rheumatologic disease. Despite being rare, drug-associated episcleritis and scleritis should also be included in the differential diagnosis. Tumor necrosis factor-alpha (TNF-α) inhibitors are generally well-tolerated, but etanercept, in particular, has the potential to cause paradoxical adverse reactions including ocular inflammations, such as uveitis, scleritis, and ocular myositis. Etanercept differs in its mechanism of action from other TNF-α inhibitors as it acts as a decoy receptor, and this may partly explain the more frequently reported etanercept-associated ocular inflammation. Etanercept may also be ineffective in preventing ocular inflammation. However, the dechallenge and rechallenge phenomena have proven there is a causative link between etanercept and new-onset ocular inflammation. We report a case of a 15-year-old boy with enthesitis-related arthritis and familial Mediterranean fever who presented with episcleritis and blepharitis while receiving etanercept treatment and subsequently showed dechallenge and rechallenge reactions. Therefore, physicians should also be aware that episcleritis should be considered a paradoxical adverse reaction to etanercept and can occur in pediatric patients. We also reviewed the English literature to provide an overview and evaluate intervention options.