Predominant Lower Lobe Bronchiectasis as a Manifestation of Primary Antibody Deficiency: A Case Emphasizing the Need for Immunological Screening

A bstract Bronchiectasis is commonly attributed to post-infectious or post-tubercular causes in developing countries. However, primary immunodeficiency, particularly primary antibody deficiencies, is an important yet under-recognized etiology. Early identification is critical, as immunoglobulin replacement therapy reduces infection frequency and may prevent disease progression. Here, we report a 14-year-old male with recurrent lower respiratory tract and skin infections since childhood who presented with chronic productive cough. High-resolution computed tomography of the thorax revealed left lower lobe cystic bronchiectasis. Microbiological workup was negative for mycobacterial and pseudomonal infection. Immunological evaluation demonstrated markedly reduced serum immunoglobulin (Ig) levels (IgG: 14.9 mg/dL, IgA: 6.64 mg/dL, and IgE: 0.10 mg/dL) with preserved cluster of differentiation (CD)3 and CD19 populations on flow cytometry. Secondary causes of hypogammaglobulinemia were excluded. A diagnosis of probable common variable immunodeficiency was made, and the patient was initiated on intravenous immunoglobulin therapy with significant clinical improvement. This case report underscores the importance of routine immunological screening in adolescents with unexplained bronchiectasis and recurrent infections.