Immunodeficiency disorders: primary and secondary MCQs With Answer

This set of MCQs on immunodeficiency disorders—both primary and secondary—has been prepared for M.Pharm students to reinforce advanced concepts in immunopathology, diagnostics, and therapeutic management. Questions cover genetic etiologies, laboratory tests, clinical presentation, pharmacologic interventions (including immunoglobulin replacement, enzyme therapy, and prophylactic antimicrobials), transplantation and gene therapy options, and implications for vaccination and drug safety. Emphasis is placed on interpretation of immune workup (immunoglobulin levels, lymphocyte subsets, neutrophil function assays, complement assays), distinguishing features between humoral, cellular and phagocytic defects, and common secondary causes such as HIV, cytotoxic drugs, and malnutrition—useful for clinical decision-making and therapeutics in a pharmacy practice context.

Q1. Which feature best distinguishes X-linked (Bruton) agammaglobulinemia from common variable immunodeficiency (CVID)?

• Onset in infancy with almost absent B cells and very low immunoglobulins
• Variable age of onset with low immunoglobulins and normal B-cell counts
• Markedly elevated IgE and eosinophilia
• Isolated IgA deficiency with normal IgG and IgM

Correct Answer: Onset in infancy with almost absent B cells and very low immunoglobulins

Q2. Which laboratory test is most appropriate to screen newborns for severe combined immunodeficiency (SCID)?

• Serum immunoglobulin quantification (IgG, IgA, IgM)
• T-cell receptor excision circles (TREC) assay
• Complement CH50 assay
• Nitroblue tetrazolium (NBT) test

Correct Answer: T-cell receptor excision circles (TREC) assay

Q3. A patient with chronic granulomatous disease (CGD) will characteristically have which abnormal laboratory finding?

• Absent B cells by flow cytometry
• Negative dihydrorhodamine (DHR) or abnormal oxidative burst on neutrophil testing
• Low serum C3 levels with recurrent meningococcal infections
• Profound lymphopenia affecting both T and B cells

Correct Answer: Negative dihydrorhodamine (DHR) or abnormal oxidative burst on neutrophil testing

Q4. Which immunodeficiency is most commonly associated with an increased risk of severe streptococcal and staphylococcal bacterial infections due to defective opsonization by complement?

• C3 deficiency
• Severe combined immunodeficiency (SCID)
• Common variable immunodeficiency (CVID)
• Hyper-IgE syndrome (Job syndrome)

Correct Answer: C3 deficiency

Q5. Which of the following management options is first-line therapy for patients with X-linked agammaglobulinemia to prevent recurrent infections?

• Monthly intravenous immunoglobulin (IVIG) replacement therapy
• Long-term systemic corticosteroids
• High-dose antifungal prophylaxis with fluconazole
• BCG vaccination to stimulate innate immunity

Correct Answer: Monthly intravenous immunoglobulin (IVIG) replacement therapy

Q6. Which statement best describes the typical immunoglobulin profile in hyper-IgM syndrome?

• Low IgM with high IgG and IgA due to class-switch hyperactivity
• Normal or elevated IgM with low IgG and low IgA due to defective class-switch recombination
• Isolated IgA deficiency with preserved IgG and IgM
• Markedly elevated IgE with normal IgG and IgM

Correct Answer: Normal or elevated IgM with low IgG and low IgA due to defective class-switch recombination

Q7. Which secondary immunodeficiency is most directly associated with chronic corticosteroid therapy?

• Reduced neutrophil count leading to neutropenia
• Functional lymphopenia with reduced T-cell responses and impaired humoral immunity
• Selective IgA deficiency
• Inherited complement deficiency

Correct Answer: Functional lymphopenia with reduced T-cell responses and impaired humoral immunity

Q8. For a patient with suspected complement deficiency leading to recurrent Neisseria infections, which diagnostic assay is most informative?

• Measurement of serum immunoglobulin levels (IgG, IgM, IgA)
• Total hemolytic complement assay (CH50) and terminal complement component testing
• T-cell receptor excision circles (TREC) screening

Correct Answer: Total hemolytic complement assay (CH50) and terminal complement component testing

Q9. Which therapeutic approach is an approved enzyme replacement for ADA-deficient SCID?

• Pegylated adenosine deaminase (PEG-ADA) enzyme replacement
• Monthly intravenous immunoglobulin only
• High-dose interferon-gamma injections
• Rituximab to deplete dysfunctional B cells

Correct Answer: Pegylated adenosine deaminase (PEG-ADA) enzyme replacement

Q10. Which vaccination recommendation is most appropriate for a patient with severe combined immunodeficiency (SCID)?

• Administer all routine live attenuated vaccines cautiously with prophylactic antivirals
• Avoid live vaccines until immune reconstitution after definitive therapy
• Give double doses of inactivated vaccines to improve response
• Administer BCG at birth to prevent mycobacterial infections

Correct Answer: Avoid live vaccines until immune reconstitution after definitive therapy

Q11. Which clinical presentation is most characteristic of patients with selective IgA deficiency?

• Recurrent sinopulmonary infections, allergic disease and increased risk of transfusion reactions due to anti-IgA antibodies
• Severe opportunistic viral infections typical of T-cell defects
• Recurrent deep-seated fungal infections typical of neutrophil defects
• Neonatal severe infections due to absent maternal antibodies

Correct Answer: Recurrent sinopulmonary infections, allergic disease and increased risk of transfusion reactions due to anti-IgA antibodies

Q12. Which drug used in transplantation most commonly causes secondary immunodeficiency by inhibiting calcineurin and T-cell activation?

• Ciclosporin or tacrolimus
• Azathioprine
• Mycophenolate mofetil
• Rituximab

Correct Answer: Ciclosporin or tacrolimus

Q13. In chronic granulomatous disease prophylaxis, which combination is recommended to reduce severe infections?

• Prophylactic TMP-SMX and itraconazole (or posaconazole) with interferon-gamma in selected patients
• Monthly IVIG and high-dose corticosteroids
• Long-term broad-spectrum antibiotics plus live attenuated vaccines
• Administering intravenous amphotericin B prophylactically

Correct Answer: Prophylactic TMP-SMX and itraconazole (or posaconazole) with interferon-gamma in selected patients

Q14. Which genetic defect is classically responsible for Wiskott-Aldrich syndrome?

• Mutation in the WAS gene affecting cytoskeletal regulation in hematopoietic cells
• Defect in the BTK gene causing absent B-cell development
• Complement C5-C9 deficiency leading to meningococcal susceptibility
• Autosomal recessive defect in NADPH oxidase complex

Correct Answer: Mutation in the WAS gene affecting cytoskeletal regulation in hematopoietic cells

Q15. Which laboratory finding would most likely be seen in Common Variable Immunodeficiency (CVID)?

• Low immunoglobulin levels (IgG ± IgA/IgM) with poor specific antibody responses despite normal or low B-cell counts
• Absent thymic shadow and absent T cells on flow cytometry
• Absent oxidative burst in neutrophils
• Isolated deficiency of complement C1 esterase

Correct Answer: Low immunoglobulin levels (IgG ± IgA/IgM) with poor specific antibody responses despite normal or low B-cell counts

Q16. Which opportunistic infection is classically associated with profound CD4+ T-cell depletion as seen in advanced HIV infection?

• Pneumocystis jirovecii pneumonia (PCP)
• Recurrent pyogenic otitis media
• Chronic granulomatous bacterial abscesses
• Early-onset severe eczema

Correct Answer: Pneumocystis jirovecii pneumonia (PCP)

Q17. Which statement about intravenous immunoglobulin (IVIG) therapy is correct for primary antibody deficiencies?

• IVIG dosing is typically individualized and monitoring trough IgG levels guides dosing and interval adjustments
• IVIG is contraindicated in all patients with selective IgA deficiency
• Oral immunoglobulin replacement is equally effective as IVIG for systemic protection
• Single fixed dose of IVIG is sufficient for lifelong protection without monitoring

Correct Answer: IVIG dosing is typically individualized and monitoring trough IgG levels guides dosing and interval adjustments

Q18. Which clinical scenario most strongly suggests a phagocytic (neutrophil) defect rather than an antibody deficiency?

• Recurrent deep tissue abscesses with catalase-positive organisms and granuloma formation
• Frequent sinopulmonary infections with encapsulated bacteria responding to IVIG
• Chronic mucocutaneous candidiasis due to T-cell defect
• Isolated viral infections such as recurrent HSV without bacterial disease

Correct Answer: Recurrent deep tissue abscesses with catalase-positive organisms and granuloma formation

Q19. Which of the following drugs is most likely to cause secondary hypogammaglobulinemia through B-cell depletion?

• Rituximab (anti-CD20 monoclonal antibody)
• Ciclosporin
• Systemic corticosteroids
• Calcineurin inhibitors like tacrolimus

Correct Answer: Rituximab (anti-CD20 monoclonal antibody)

Q20. In a patient with recurrent severe infections and absent tonsillar tissue, which primary immunodeficiency diagnosis is most likely?

• Agammaglobulinemia (e.g., X-linked agammaglobulinemia)
• Selective IgA deficiency
• Chronic granulomatous disease
• Complement C2 deficiency

Correct Answer: Agammaglobulinemia (e.g., X-linked agammaglobulinemia)

Download