Primary immunodeficiency flashcards
5 high-yield MRCP Part 1 cards from the Intellect Medicos Haematology & Oncology course. Try to answer each question before you open it — then study them properly with spaced repetition, which brings each card back just before you would forget it.
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What is the most common primary immunodeficiency?
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Selective IgA deficiency.
Why? B cells fail to switch to making IgA; many people have no symptoms, others have recurrent sinopulmonary infections and Giardia diarrhoea.
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How should coeliac serology be done in a patient with IgA deficiency?
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Use IgG-based tests — IgG tTG, IgG EMA or IgG DGP.
Why? IgA tTG is falsely negative when no IgA is made, which is why total IgA is measured alongside IgA tTG first.
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Which gene is mutated in X-linked (Bruton) agammaglobulinaemia?
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BTK (Bruton tyrosine kinase).
Why? Without BTK, B-cell maturation stops in the marrow, so B cells and all immunoglobulin classes are almost absent.
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DiGeorge syndrome is caused by a ______ deletion, with failure of the 3rd and 4th pharyngeal pouches.
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22q11.2
Why? Thymic aplasia causes T-cell deficiency (viral and fungal infections); absent parathyroids cause neonatal hypocalcaemic seizures.
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Which test diagnoses chronic granulomatous disease?
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Dihydrorhodamine (DHR) flow cytometry test, showing an absent neutrophil oxidative burst.
Why? NADPH oxidase deficiency stops neutrophils making reactive oxygen species, so they cannot kill catalase-positive organisms (S. aureus, Aspergillus, Serratia, Nocardia).