Supplementary Material for: A Novel Case of Multicentric Reticulohistiocytosis Associated with Renal Cell Carcinoma Successfully Treated with Infliximab and Methotrexate

Multicentric reticulohistiocytosis (MRH) is categorized as a rare non-Langerhans cell histiocytosis most commonly seen in women in the fourth to fifth decade of life. This systemic inflammatory condition affects multiple organ systems and can result in severe joint destruction which can progress to arthritis mutilans. To date, various underlying malignancies have been discovered in patients with MRH including breast, gastric, thymic, hepatic, and melanoma. There has been 1 case of underlying renal cell carcinoma reported in a patient diagnosed with MRH. Additionally, there is no consistently recognized treatment for MRH described in the literature. The rarity of the disease contributes to the difficulty in defining a standardized treatment. We present the case of a patient with extensive joint and skin involvement who was successfully treated with infliximab and methotrexate, experienced clinical improvement, and was later diagnosed with clear cell renal cell carcinoma. The synergistic effects of infliximab and methotrexate, in combination with the low side-effect profile, appear to be promising in the setting of MRH and in our patient resulted in the resolution of symptoms and cutaneous manifestations. We suggest this regimen as an effective combination therapy. We emphasize thorough and continuous screening for underlying malignancy associated with MRH, despite clinical improvement or negative malignancy work-up upon initial diagnosis.