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

Abstract

Backgorund

Pachydermoperiostosis, also known as primary hypertrophic osteoarthropathy, is a rare disease classically characterized by skin thickening, digital clubbing, and periostosis. However, in some cases, the disease may present with joint pain, synovitis, and elevated inflammatory markers, thereby mimicking inflammatory rheumatologic diseases. When thoracic pathological findings are present, distinguishing primary from secondary hypertrophic osteoarthropathy is of particular clinical importance.

Case presentation

We present a male patient born in 1989. The patient underwent a stepwise evaluation in Azerbaijan, Germany, and Turkey because of long-standing joint complaints and systemic inflammatory activity. Available medical records documented persistently elevated C-reactive protein and erythrocyte sedimentation rate, recurrent anemia, hypergammaglobulinemia, and, on a left knee magnetic resonance imaging report, synovitis, increased intra-articular fluid, and bone marrow edema. Because the chest computed tomography report described bilateral pleural effusion, infiltrative changes in the lung parenchyma, and a subpleural solid nodule, the possibility of secondary hypertrophic osteoarthropathy was also considered. After insufficient response to etoricoxib and a tumor necrosis factor inhibitor, tocilizumab was initiated at a weekly subcutaneous dose of 162 mg, and marked clinical and laboratory improvement was observed within approximately six weeks. However, a flare of furunculosis-like skin lesions caused significant psychological distress and led the patient to discontinue treatment.

Conclusion

This case suggests that a clinical picture compatible with the pachydermoperiostosis/hypertrophic osteoarthropathy spectrum may present with active inflammatory arthritis and systemic inflammation. Although the response to tocilizumab suggests a possible role for individualized biologic treatment in selected inflammatory phenotypes, cutaneous flare and psychological burden may limit treatment adherence.