Chapter 63: Immunological Disorders

Type 1 hypersensitivity encompasses immediate allergic reactions mediated by immunoglobulin E, ranging from localized manifestations of atopy to severe systemic anaphylaxis requiring emergency intervention with epinephrine. Type 2 reactions involve cytotoxic antibodies binding to cellular antigens, while Type 3 reactions feature circulating immune complexes that deposit in tissues causing inflammation. Type 4 hypersensitivity represents delayed cell-mediated responses occurring days after antigen exposure. The chapter then transitions to rheumatoid arthritis, a chronic systemic inflammatory condition characterized by symmetric polyarthritis and progressive joint destruction through pannus formation, with management strategies encompassing physical therapy, nonsteroidal anti-inflammatory drugs, and disease-modifying antirheumatic drugs such as methotrexate. Subsequent sections address chronic fatigue syndrome and fibromyalgia, which present as overlapping conditions with significant functional impairment managed through cognitive-behavioral approaches and pharmacological interventions. Sjögren's syndrome is presented as an autoimmune disorder affecting exocrine glands, producing characteristic sicca symptoms with diagnostic confirmation through serological markers and tissue biopsy. The chapter concludes with systemic lupus erythematosus, a multisystem autoimmune disease with varied organ involvement including lupus nephritis, requiring comprehensive immunosuppressive therapy and hydroxychloroquine as foundational treatment. Throughout, the chapter emphasizes diagnostic criteria, pathophysiological mechanisms, and contemporary therapeutic approaches appropriate for primary care settings.