Pachydermoperiostosis: studies on the synovium.

: Pachydermoperiostosis (primary hypertrophic osteoarthropathy) is a familial disorder characterized by clubbing, periosteal bone changes, and furrowing of the skin. A 40 year old male with this syndrome and chronic arthritis was recently studied. The synovial fluid was non-inflammatory. Histologically the synovium exhibited hyperplasia and microvascular alterations. Immunofluorescent staining failed to identify deposits of immunoglobulin. Electron microscopy revealed multilayered basement laminae around small subsynovial blood vessels but no electron-dense deposits as described in studies of hypertrophic pulmonary osteoarthropathy. The pathogenesis is obscure and appears to be non-immunological.