Immunodeficiencies in Adults: Key Considerations for Diagnosis and Management.

Immunodeficiencies in adults are increasingly recognized yet often remain underdiagnosed, leading to significant morbidity from recurrent infections, autoimmunity, and malignancy. Both primary immunodeficiencies (PIDs), now known as inborn errors of immunity (IEI), and secondary immunodeficiencies (SIDs) contribute to immune dysfunction in adults. Although SIDs are more common in adults due to factors like medications, malignancies, metabolic disorders, chronic conditions, and protein-losing conditions, IEI-particularly common variable immunodeficiency (CVID)-can also manifest in adulthood with diverse clinical features. Early recognition is crucial, with key warning signs including recurrent sinopulmonary infections, unexplained autoimmunity, poor vaccine responses, chronic diarrhea, bronchiectasis, and persistent lymphadenopathy. The diagnostic approach should be systematic. It begins with a detailed patient history and status followed by the evaluation of immunoglobulin levels, lymphocyte subsets, vaccine-specific antibody responses, and exclusion of secondary causes. Genetic testing, increasingly accessible, plays an important role in confirming the diagnosis of IEI and guiding prognosis and treatment. Management strategies focus on treating the underlying condition in SIDs. Preventive measures, including antimicrobial prophylaxis, vaccination, and immunoglobulin replacement therapy (IGRT) in patients with significant antibody deficiencies, are essential for reducing infections and complications in high-risk patients. Given the growing recognition of adult-onset immunodeficiency, clinicians should maintain a high index of suspicion and adopt a structured diagnostic and management approach to improve patient outcomes and quality of life.