Multicentric reticulohistiocytosis associated arthritis responding to anti-TNF and methotrexate.

We present a patient with therapy resistant multicentric reticulohistiocytosis (MRH). MRH is a rare granulomatous, multisystem disease characterised most frequently by disfiguring papulonodular skin lesions and sometimes a destructive polyarthritis, though any organ can be involved. Abnormal histiocytic reactions to an undetermined stimulus (possibly an associated mycobacterial infection, auto immune process or neoplastic process) have been proposed as an underlying mechanism. The diagnosis is confirmed by histopathology of the cutaneous nodules and/or synovial membrane by the presence of CD68-positive histiocytes and multinucleated giant cells with an eosinophilic 'ground-glass' cytoplasm. Recent studies have identified TNFalpha and other inflammatory cytokines to be highly expressed in the synovium and synovial fluid of affected joints in patients with MRH. Based on these findings, we treated our patient with infliximab in combination with methotrexate with marked improvement of morning stiffness, tender and swollen joint count, visual analogue scale and health assessment questionnaire after his third infusion. However, the nodules did not markedly resolve. When treating patients with MRH with TNFa neutralizing drugs, one has to keep the possible association with malignancy in 15-30% of cases in mind and these products should be used with caution.