Book excerpt: This issue of Immunology and Allergy Clinics, guest edited by Dr. Mark Ballow and Dr. Elena Perez, will provide up-to-date clinical concepts regarding Immunodeficiencies. Articles in this outstanding issue include: Precision Medicine for Patients with Primary Immune Dysregulation, Immune Disorders Associated with Abnormalities in Treg Cells, Defining Common Variable Immunodeficiency, The Importance of Primary Immune Deficiency Registries, Chronic Lung Disease in Primary Antibody Deficiency: Diagnosis and Management, Immune Deficiencies Associated with Th17 Immunity, Truths and Myths of Vaccines in Patients with Primary Immune Deficiency, The Nuts and Bolts of Subcutaneous Immunoglobulin Replacement Therapy, Newly Discovered Primary Immune Deficiencies, and Specific Antibody Deficiency.