Delayed Diagnosis of Common Variable Immunodeficiency Revealed by Recurrent Respiratory Infections and Persistent Mediastinal Lymphadenopathy: A Case Report.

Common variable immunodeficiency (CVID) is the most common symptomatic primary immunodeficiency in adults and is characterized by impaired antibody production, hypogammaglobulinemia, and recurrent infections. Owing to its marked clinical heterogeneity, the diagnosis is frequently delayed, particularly in patients presenting with atypical manifestations. We report the case of a 57-year-old woman who presented with recurrent lower respiratory tract infections associated with persistent mediastinal lymphadenopathy. Initial chest computed tomography revealed a right-sided pneumonic consolidation with centrilobular tree-in-bud micronodules. Follow-up imaging demonstrated complete resolution of the pulmonary micronodules but persistent mediastinal lymphadenopathy, prompting extensive investigations. Histopathological examination of an axillary lymph node showed reactive follicular hyperplasia, while microbiological investigations, including Xpert MTB/RIF and bronchoalveolar lavage cultures, were negative. Further evaluation excluded sarcoidosis, hematological malignancy, and other infectious causes. Serum protein electrophoresis revealed marked hypogammaglobulinemia, and quantitative immunoglobulin testing demonstrated markedly decreased serum IgG (0.98 g/L; reference range: 7-16 g/L) and complete IgA deficiency (0 g/L; reference range: 0.7-4.0 g/L), establishing the diagnosis of CVID. This case highlights the diagnostic challenge posed by late-presenting CVID and emphasizes that recurrent respiratory infections associated with persistent lymphadenopathy should prompt consideration of an underlying primary immunodeficiency, even in older adults. Early recognition and timely initiation of immunoglobulin replacement therapy are essential to prevent irreversible pulmonary complications and improve long-term outcomes.