This comprehensive book provides an in-depth exploration of rheumatology within the context of internal medicine, focusing on autoimmune and inflammatory diseases that affect both musculoskeletal and systemic functions. The text begins with an introduction to rheumatology, emphasizing the integration of clinical evaluation, pathophysiology, and diagnostic reasoning in the management of complex systemic disorders. Early chapters detail the immune system and the pathogenesis of autoimmune diseases, explaining how dysregulation of innate and adaptive immunity, autoantibody production, and cytokine imbalances contribute to chronic inflammation and organ damage. This foundational knowledge sets the stage for understanding the clinical presentation and progression of rheumatologic conditions. Subsequent sections address clinical evaluation in rheumatology, highlighting the importance of thorough patient history, physical examination, and diagnostic modalities including laboratory investigations and imaging. Specific disease chapters focus on systemic lupus erythematosus, rheumatoid arthritis, scleroderma and systemic sclerosis, and Sjögren’s syndrome, providing insights into their characteristic clinical features, immunopathology, and therapeutic strategies. The text also examines spondyloarthropathies, including ankylosing spondylitis, psoriatic arthritis, reactive arthritis, and enteropathic arthritis, emphasizing their overlapping genetic, immunologic, and inflammatory mechanisms. Vasculitides are discussed in detail, with separate coverage of large, medium, and small vessel vasculitis, highlighting their systemic impact and the role of early recognition in preventing severe complications. Mixed connective tissue disease and overlap syndromes are explored to illustrate the spectrum of autoimmune presentations and the challenges inherent in diagnosis and management. The book also delves into autoinflammatory syndromes, emphasizing the distinction from classic autoimmune disorders and the unique molecular pathways involved. Pharmacologic management is thoroughly covered, from traditional anti-inflammatory agents to disease-modifying antirheumatic drugs, biologics, and targeted therapies. Emerging therapies and precision medicine approaches are highlighted, reflecting the evolving landscape of rheumatology and the promise of individualized treatment strategies. The text addresses rheumatologic emergencies and the special considerations required for populations such as pediatric, geriatric, and pregnant patients. Emphasis is placed on interdisciplinary care, integrating rheumatologists, immunologists, primary care providers, and allied health professionals to optimize outcomes.