Janus Kinase Inhibitor Upadacitinib in Elderly-Onset Rheumatoid Arthritis With Hip Osteoarthritis: A Case Report.

BACKGROUND Evaluating hip pain in older adult patients is challenging when elderly-onset rheumatoid arthritis (EORA) develops on a background of end-stage osteoarthritis (OA). Although disease-modifying antirheumatic drugs suppress inflammation, radiographic structural improvement in the hip is rarely reported. This report describes a 78-year-old man with end-stage hip OA in whom EORA developed and responded to the Janus kinase (JAK) inhibitor upadacitinib (UPA). CASE REPORT A 78-year-old man with end-stage right hip OA developed polyarthritis and was diagnosed with EORA. Despite corticosteroids and multiple conventional disease-modifying antirheumatic drugs, disease activity remained high (C-reactive protein [CRP], 7.22 mg/dL; Simplified Disease Activity Index, 22.2; Disease Activity Score 28-CRP, 4.4). Methotrexate was avoided due to interstitial changes on chest radiography. UPA was initiated 6 months after presentation, resulting in marked clinical improvement and corticosteroid discontinuation at 9 months. Under UPA monotherapy, the Simplified Disease Activity Index decreased to 3.0 and Disease Activity Score 28-CRP to 1.5, with hip-related symptoms improving. Follow-up radiographs suggested subtle improvement in the appearance of joint space narrowing at 2 months, with improved delineation of the subchondral bone by 6 months. Although the patient initially declined surgery owing to symptom relief, persistent gait disturbance required total hip arthroplasty. Intraoperative findings showed only mild synovial inflammation. CONCLUSIONS This case indicates that, in end-stage hip OA complicated by EORA, tight inflammatory control with UPA can be associated with symptomatic improvement and radiographic changes. When hip OA and EORA coexist, repeat imaging after inflammation is tightly suppressed may aid interpretation of persistent pain and structural findings.