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X-Linked Agammaglobulinaemia — RACP Adult Medicine MCQ

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HardInfectious DiseasesX-Linked AgammaglobulinaemiaRACP Adult Medicine

A 32-year-old has recurrent bacterial sinus and lung infections, Giardia, bronchiectasis, very low IgG and IgA, poor vaccine responses and normal circulating B-cell numbers. What is the most likely primary immunodeficiency?

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Correct answer: B — Common variable immunodeficiency

The best answer is “Common variable immunodeficiency”. CVID typically presents in adolescence or adulthood with hypogammaglobulinaemia, impaired specific-antibody responses and recurrent sinopulmonary or gastrointestinal infection despite B cells being present. X-linked agammaglobulinaemia usually presents in boys with absent B cells. Immunoglobulin replacement and infection, lung, autoimmune and malignancy monitoring require immunology care.

Reference: ASCIA: Common variable immunodeficiency: https://www.allergy.org.au/images/pc/ASCIA_PC_PID-IEI_CVID_FAQ_2025.pdf