Cutaneous lesions and articular manifestations in multicentric reticulohistiocytosis: a diagnostic challenge.

A 56-year-old woman presented with a one-year history of polyarthralgia and skin lesions. Examination revealed polyarthritis and reddish-brown nodules on interphalangeal (IF) joints. Histopathology confirmed a diagnosis of multicentric reticulohistiocytosis (MRH) with characteristic histiocytes and multinucleated giant cells positive for PAS, PASD, CD45, and CD68. Imaging showed periarticular osteopenia and erosions. Immunosuppressive therapy with prednisolone (PDN) and methotrexate (MTX) led to significant improvement in symptoms within two months. MRH, a rare non-Langerhans cell histiocytosis, is marked by papulonodular skin lesions and symmetric polyarthritis, potentially erosive. It may be associated with rheumatic diseases and necessitates malignancy screening. Diagnosis is based on clinical and histological findings due to the absence of specific biomarkers. Immunosuppressive treatment remains the cornerstone of management.