Langerhans cell granulomatosis manifested as pigmented villonodular synovitis.

We report an unusual case of Langerhans cell granulomatosis (LCG) manifested as a villous synovial proliferation in a 38-year-old female jogger. One year after the onset of joint symptoms, she had a classical LCG presentation with skin and visceral lymph node involvement. Review of the literature revealed only one case of synovial shoulder joint tenosynovitis associated with LCG in a middle-aged woman. Ours is the first reported case presenting clinically in the synovium of the hip joint as pigmented villonodular synovitis. Histiocytic/dendritic proliferations involving the synovial tissues are not uncommon. These lesions as well as the rare multicentric reticulohistiocytosis (MRH), a systemic monocytoid/histiocytic disorder with multinucleated giant cells, polyarthritis, and papulonodular skin lesions, should be considered in the differential diagnosis. Clinical and pathologic features will distinguish LCG from MRH.