Autoantibodies are a very heterogeneous group of antibodies with respect to their specificity, induction, effects, and clinical significance. Testing for autoantibodies can be helpful or necessary for the diagnosis, differential diagnosis, prognostication, or monitoring of autoimmune diseases. In case of limited (forme fruste) disease or a single disease manifestation, the detection of serum autoantibodies can play an important role in raising the suspicion of evolving disease and forecasting prognosis. This book and reference guide is intended to assist the physician in understanding and interpreting the variety of autoantibodies that are being used as diagnostic and prognostic tools for patients with systemic rheumatic diseases. Autoantibodies observed in systemic autoimmune diseases are described in alphabetical order in Part 1 of this reference guide. In Part 2, systemic autoimmune disorders as well as symptoms that indicate the possible presence of an autoimmune disease are listed. Systemic manifestations of organ-specific autoimmune diseases will not be covered in this volume. Guide marks were inserted to ensure fast and easy cross-reference between symptoms, a given autoimmune disease and associated autoantibodies. Although the landscape of autoantibody testing continues to change, this information will be a useful and valuable reference for many years to come.