A refractory polyarthritis revealing a multicentric reticulohistiocytosis

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