A refractory polyarthritis revealing a multicentric reticulohistiocytosis.

Multicentric reticulohistiocytosis is a rare, non-Langerhans cell histiocytosis characterised by papulonodular skin lesions and a rapidly progressive, erosive polyarthritis. We describe the case of a 51-year-old man who presented with a 6 months of acute inflammatory polyarthralgia, synovitis, and extensor tenosynovitis. Concurrently, multiple papulonodular lesions developed on his hands, face, and auricular regions. A skin biopsy demonstrated CD68-positive histiocytes and multinucleated giant cells with eosinophilic 'ground-glass' cytoplasm, confirming multicentric reticulohistiocytosis. Treatment with corticosteroids and methotrexate was ineffective, whereas tumour necrosis factor-alpha inhibitor therapy resulted in meaningful clinical improvement and steroid sparing. Early recognition, imaging, and a biopsy are essential to avoid irreversible joint damage. Although therapeutic evidence is limited to case reports, biologic agents targeting pro-inflammatory cytokines may offer a significant benefit. Awareness of multicentric reticulohistiocytosis is crucial for timely diagnosis and management.