The synovial fluid fibroblast-like synoviocyte: A long-neglected piece in the puzzle of rheumatoid arthritis pathogenesis.

Rheumatoid arthritis (RA) is a systemic autoimmune disease during which fibroblast-like synoviocytes (FLS) contribute to both joint inflammation and destruction. FLS represent the core component of the synovial membrane. Following inflammation of this membrane, an effusion of cell-rich synovial fluid (SF) fills the joint cavity. Unlikely, SF has been shown to contain fibroblasts with some shared phenotypic traits with the synovial membrane FLS. These cells are called SF-FLS and their origin is still unclear. They are either brought into the synovium via migration through blood vessels, or they could originate within the synovium and exist in projections of the synovial membrane. SF-FLS function and phenotype are poorly documented compared to recently well-characterized synovial membrane FLS subsets. Furthermore, no study has yet reported a SF-FLS single-cell profiling analysis. This review will discuss the origin and cellular characteristics of SF-FLS in patients with RA. In addition, recent advances on the involvement of SF-FLS in the pathogenesis of RA will be summarized. Current knowledge on possible relationships between SF-FLS and other types of fibroblasts, including synovial membrane FLS, circulating fibrocytes, and pre- inflammatory mesenchymal (PRIME) cells will also be addressed. Finally, recent therapeutic strategies employed to specifically target SF-FLS in RA will be discussed.

A Rare Case of Hypophosphataemic Osteomalacia in von Recklinghausen Neurofibromatosis.

BACKGROUND: Neurofibromatosis type 1 (NF1), also known as von Recklinghausen disease, is a one of the more common hereditary autosomal disorders. However, osteomalacia in neurofibromatosis type 1 is very rare tumour-induced osteomalacia; fibroblast growth factor-23 is usually implicated. PATIENTS AND METHODS: We report the case of a patient with a history of von Recklinghausen neurofibromatosis who presented with hypophosphataemic osteomalacia. RESULTS: The patient was treated with high-dose calcitriol and oral phosphate with clinical improvement. CONCLUSION: Even though it is a rare entity, we must consider the diagnosis of hypophosphataemic osteomalacia in patients with neurofibromatosis in order to deliver appropriate treatment. LEARNING POINTS: Osteomalacia during von Recklinghausen disease is a rare presentation of an uncommon condition and has a poorly understood mechanism.The treatment of oncogenic osteomalacia includes tumour removal which, however, is not always possible.Administration of calcitriol alone is not sufficient and phosphorus intake is mandatory to improve symptoms.

[Osteomalacia and giant cell tumor: a rare case]. / Ostéomalacie et tumeur a cellule géante: une entité rare.

BACKGROUND: Oncogenic octeomalacia is an unusual and rare clinicopathologic syndrome characterized by mesenchymal tumors that apparently produce osteomalacia and biochemical abnormalities consisting of hypophosphatemia and normocalcemia. AIM: We have investigated the mechanism by which a giant cell tumor of bone caused biopsy-proved osteomalacia in a 50-year-old woman. CASE REPORT: A 50-year-old woman presented with generalized bone and pelvicrural pain, associated with fatiguability and muscle weakness. The diagnosis of osteomalacia was retained, associated with a giant cell tumor. The coexistence of giant cell tumor of bone and osteomalacia suggested the diagnosis of oncogenic osteomalacia. Resolution of the biochemical abnormalities of the syndrome after tumor resection, established this diagnosis. CONCLUSION: oncogenic osteomalacia can be a form of vitamin-D-refractory osteomalacia due to altered vitamin D3 metabolism.