A 56-year-old woman presented with changes characteristic of the reflex sympathetic dystrophy syndrome (RSDS) but also frank synovitis of the left wrist, an elevated ESR and early damage of the left carpus on radiographs, suggesting septic arthritis. A dynamic scan showed changes characteristic of RSDS. A sample of synovium and bone from the wrist showed non-specific inflammation with partial destruction of cartilage by synovial pannus and involvement of subchondral bone by the inflammatory process. The search for the cause of infection was unsuccessful. Patchy osteopaenia developed 3 months after onset. At the 12 month follow-up, the course of disease was compatible with RSDS and destruction of the carpus had not progressed. Attention is drawn to the difficulty in reaching a precise diagnosis in early stages and the need to exclude infection.