This book is a practical, user-friendly guide for diagnosing and treating patients with rare rheumatic diseases of immunologic dysregulation. Covering uncommon diseases such as IgG4-Related Disease, Castleman’s Disease, and Felty Syndrome, chapters aggregate information from case reports and anecdotal literature to create a single, comprehensive handbook for treating patients. Each chapter provides historical perspective and epidemiology; a literature review (including research trials, translational research, historical and current case reports, and case series); pathogenesis; clinical presentation; laboratory evaluation; imaging; histopathology; treatment; and outcomes. Rare Rheumatic Diseases of Immunologic Dysregulation is an invaluable resource for rheumatologists, rheumatology fellows, and clinical immunologists to better diagnose and treat patients with rare rheumatic diseases.