Question 1

Which of the following is a hallmark clinical sign that should raise suspicion for a primary immunodeficiency (PID) in a child?

Accepted Answer

Eight respiratory tract infections per year

Question 2

A 3-month-old male infant presents with chronic diarrhea, skin rashes, and recurrent infections. Laboratory tests reveal very low T and NK cell counts, and defective B cells. Which genetic mutation is most likely responsible for this condition?

Accepted Answer

Mutation in the IL2RG gene at the Xq13.1 locus

Question 3

Which of the following best describes the inheritance pattern of X-linked Severe Combined Immunodeficiency (X-SCID)?

Accepted Answer

X-linked recessive

Question 4

A patient with CD40 ligand (CD40L) deficiency is most likely to have which immunoglobulin profile?

Accepted Answer

Increased IgM, decreased IgA, IgG, and IgE

Question 5

Which of the following is a common causative microbe in patients with primary antibody deficiencies?

Accepted Answer

Streptococcus pneumoniae

Question 6

A 4-year-old girl presents with recurrent anemia, rash, hepatosplenomegaly, and failure to thrive. Her complement C3 and C4 levels are elevated. Which of the following is the most likely underlying issue?

Accepted Answer

Primary immunodeficiency disease

Question 7

Which of the following best explains why patients with Wiskott-Aldrich Syndrome (WAS) have an increased tendency to bleed?

Accepted Answer

Significantly reduced number of platelets

Question 8

Which of the following is a key function of the actin cytoskeleton in T cells?

Accepted Answer

Facilitating cell movement and division

Question 9

A patient with chronic granulomatous disease is most likely to have a defect in which of the following?

Accepted Answer

NADPH oxidase complex

Question 10

Which of the following treatments is considered curative for many primary immunodeficiency diseases, especially SCID and WAS?

Accepted Answer

Hematopoietic stem cell transplantation (HSCT)

Question 11

Which immunoglobulin class is most commonly deficient in the most prevalent primary immunodeficiency in northern Europeans?

Accepted Answer

IgA

Question 12

A patient with a mutation in the WAS gene is likely to have which of the following triad of symptoms?

Accepted Answer

Bleeding tendency, recurrent infections, eczema

Question 13

Which of the following best describes the role of the common gamma (γ) chain encoded by IL2RG in lymphocyte development?

Accepted Answer

It is a critical signaling component of multiple interleukin receptors

Question 14

Which of the following laboratory findings would you expect in a patient with common variable immune deficiency (CVID)?

Accepted Answer

Low serum IgG levels

Question 15

Which of the following is a potential complication of gene therapy using retroviral vectors for immunodeficiency diseases?

Accepted Answer

High rate of leukemia

Question 16

A patient with a defect in the CD40/CD40L pathway is most likely to have impaired:

Accepted Answer

Immunoglobulin isotype switching

Question 17

Which of the following is a distinguishing feature of complement deficiencies compared to other PIDs?

Accepted Answer

Increased susceptibility to Neisseria infections

Question 18

Which of the following best describes the mechanism by which Wiskott-Aldrich Syndrome protein (WASP) mutations lead to immunodeficiency?

Accepted Answer

Defective assembly of actin filaments required for microvesicle formation

Question 19

A patient with a history of recurrent Neisseria meningitidis infections is most likely to have a deficiency in which component of the immune system?

Accepted Answer

Complement proteins

Question 20

Which of the following is a recommended treatment for patients with Wiskott-Aldrich Syndrome to prevent infections?

Accepted Answer

Intravenous immunoglobulin (IVIG) administration

Primary Immunodeficiency Diseases (PIDs): Microbiology & Immunology Study Notes

Study Guide - Practice Questions

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