Inflammatory hypertrophic osteoarthropathy spectrum with response to interleukin-6 blockade and subsequent furunculosis-like cutaneous flare: a case report

Abstract

Pachydermoperiostosis, or primary hypertrophic osteoarthropathy, is a rare disorder that may present with inflammatory arthritis and systemic inflammation, occasionally mimicking rheumatologic disease. We report a male patient born in 1989 who underwent evaluation in Azerbaijan, Germany, and Turkey for long-standing joint symptoms and persistent inflammatory activity. Laboratory findings included elevated C-reactive protein and erythrocyte sedimentation rate, anemia, and hypergammaglobulinemia, while knee magnetic resonance imaging demonstrated synovitis, joint effusion, and bone marrow edema. Thoracic computed tomography abnormalities also required consideration of secondary hypertrophic osteoarthropathy. After insufficient response to etoricoxib and a tumor necrosis factor inhibitor, weekly subcutaneous tocilizumab 162 mg produced marked clinical and laboratory improvement within approximately six weeks. However, a flare of pre-existing furunculosis-like subcutaneous inflammatory lesions caused psychological distress and led to treatment discontinuation. This case highlights diagnostic and therapeutic complexity of inflammatory phenotypes within the pachydermoperiostosis/hypertrophic osteoarthropathy spectrum and emphasizes carefully monitoring cutaneous manifestations during biologic therapy