Question 1

Which of the following is associated with DiGeorge syndrome?

Accepted Answer

DiGeorge syndrome is associated with a small or missing thymus, which leads to T-cell deficiency.

Question 2

A 2-week-old girl is evaluated by a specialist because her physical appearance is abnormal.She has been hospitalized since birth.Her CD3 level is reported as 15% (normal values: 60%-80%).Her CD4 is 10% (normal values: 30%-65%).Her CD8 is 5% (normal values: 10%-40%),and her CD19 is 84% (normal values: 5%-20%).Serum immunoglobulin levels are normal.Karyotyping reveals a deletion on chromosome 22.These laboratory results support a diagnosis of:

Accepted Answer

The abnormal laboratory values, specifically the low CD3, CD4, and CD8 levels and elevated CD19 level, suggest a T-cell deficiency and B-cell overproduction, which is consistent with DiGeorge anomaly. The chromosome 22 deletion is also associated with this condition. Bruton's tyrosine kinase deficiency and Wiskott-Aldrich syndrome typically present with low levels of multiple immunoglobulin classes, which is not seen in this case. Ataxia telangiectasia usually presents with neurological symptoms, which are not mentioned in the case description.

Question 3

A patient's total IgG is in the normal range,but he suffers from recurrent infections with encapsulated bacteria such as Streptococcus pneumoniae and Haemophilus influenza.T-cell functions are all normal.What is the most likely cause of the infections?

Accepted Answer

Normal total IgG levels indicate that the patient is producing enough IgG, but the recurrent infections with encapsulated bacteria suggest a possible deficiency in the specific IgG subclasses that are responsible for opsonization of these organisms, such as IgG2 and IgG4. Common variable immunodeficiency (B) would result in a more significant deficiency in multiple immunoglobulins and would likely present with more diverse infections. Selective IgA deficiency (D) would not necessarily explain susceptibility to encapsulated bacteria. Tyrosine kinase deficiency (A) would typically present with more severe and widespread infections.

Question 4

A patient with hereditary angioedema will present with swelling in the tissues and has deficiencies in which of the following?

Accepted Answer

Hereditary angioedema is a condition caused by a deficiency or dysfunction of C1 inhibitor, leading to uncontrolled activation of the complement and clotting systems, resulting in swelling in the tissues. Deficiencies in C5, C6, C7, or C8 would not be associated with hereditary angioedema. Phagocytic cell function and mature B cells are also not directly related to this condition.

Question 5

Which of the following diseases results in an acquired or secondary immunodeficiency?

Accepted Answer

HIV infection leads to an acquired or secondary immunodeficiency, meaning the individual was not born with the immunodeficiency but developed it later in life due to the virus attacking and destroying immune cells. The other options are genetic disorders that result in primary immunodeficiencies.

Question 6

A child suspected of having an inherited humoral immunodeficiency disease is given a diphtheria/tetanus vaccine.Two weeks after the immunization,his level of antibody to the specific antigens is measured.Which result is expected for this patient if he does have this deficiency?

Accepted Answer

If the child has an inherited humoral immunodeficiency disease, the production of antibodies in response to vaccination may be impaired, leading to no change or a low level of specific antibody after two weeks.

Question 7

A male baby who has suffered from persistent Candida fungal infections and several bouts of pneumonia before the age of 6 months is found to have some developmental problems as well as low-set ears.Laboratory testing reveals an absence of T cells.What is the most likely diagnosis?

Accepted Answer

The absence of T cells suggests a T cell deficiency, which is characteristic of DiGeorge syndrome. The recurrent fungal infections and pneumonia may also be indicative of a compromised immune system. The developmental problems and low-set ears are also common features of DiGeorge syndrome. Selective IgA deficiency and common variable immunodeficiency may present with recurrent infections, but they typically do not have an absence of T cells. Waldenström macroglobulinemia is a neoplasm of B cells and would not present with a T cell deficiency.

Question 8

A 6-month-old baby has suffered from recurrent bacterial infections.Flow cytometry results indicate a lack of B cells but the presence of normally functioning T cells.Which is the most likely diagnosis?

Accepted Answer

Bruton's tyrosine kinase deficiency, also known as X-linked agammaglobulinemia, is characterized by a lack of B cells and recurrent bacterial infections, with normal T cell function.

Question 9

Delayed-type hypersensitivity skin tests are used to screen for:

Accepted Answer

Delayed-type hypersensitivity skin tests, also known as tuberculin skin tests, are used to screen for cell-mediated immunodeficiencies such as tuberculosis or other mycobacterial infections. The test evaluates the individual's reaction to an antigen (e.g., tuberculin purified protein derivative) injected into their skin. The presence of a delayed-type hypersensitivity reaction indicates that the individual has a functioning cell-mediated immune response.

Question 10

Which of the following statements about severe combined immunodeficiency is true?

Accepted Answer

Severe combined immunodeficiency (SCID) can be associated with signal transduction defects, which impair T cell development and/or function. This can lead to a lack of functional B cells, as T cells are required for optimal B cell development. SCID is characterized by low or absent levels of immunoglobulins, not hypergammaglobulinemia. Patients with SCID should not receive live virus vaccines, as they may not have a sufficient immune response to mount a protective immune response and may develop severe infections. SCID occurs in both males and females.

Question 11

Defects in oxidative burst activity can be detected using flow cytometry by labeling patient neutrophils with:

Accepted Answer

Dihydrorhodamine (DHR) is a fluorescent probe that is used to measure oxidative burst activity in neutrophils. When DHR enters the cell, it is oxidized by reactive oxygen species (ROS) generated during the oxidative burst, resulting in fluorescence. Flow cytometry can be used to measure the amount of fluorescence in individual neutrophils, allowing for detection of defects in oxidative burst activity. Nitroblue tetrazolium (NBT) is also commonly used to assess oxidative burst activity, but requires an additional step of staining the cells with the dye after activation. Purified protein derivative (PPD) and phytohemagglutinin (PHA) are not relevant for measuring oxidative burst activity.

Question 12

A nitroblue tetrazolium test shows little color in cells observed under a microscope.What disease does this finding correlate with?

Accepted Answer

A nitroblue tetrazolium test evaluates the ability of white blood cells to produce hydrogen peroxide, which is used to kill certain types of bacteria. Little to no color change in cells observed under a microscope indicates a deficiency in this ability, which is seen in patients with chronic granulomatous disease. This is due to a defect in the ability of the white blood cells to create reactive oxygen species, which are needed for bacteria to be killed.

Question 13

Decreased CD3-positive lymphocytes and a lack of responsiveness to phytohemagglutinin in the circulation are typically associated with:

Accepted Answer

Decreased CD3-positive lymphocytes and a lack of responsiveness to phytohemagglutinin in the circulation are characteristic of DiGeorge anomaly, a congenital disorder characterized by thymic hypoplasia or aplasia.

Question 14

A 9-month-old infant is seen by a physician because of a persistent skin infection.His white and red blood cell counts are normal.However,immunofixation electrophoresis indicates a low level of IgG.When the infant returns to the physician for a follow-up visit in a month,his IgG level has increased.What condition do these results indicate?

Accepted Answer

The infant's normal white and red blood cell counts suggest that the issue is not with his production of blood cells, but with his immune system. The low level of IgG indicates hypogammaglobulinemia, which is a deficiency in antibody production. The fact that his IgG levels have increased on their own suggests that this is a transient condition, rather than a permanent immunodeficiency. Common variable immunodeficiency and DiGeorge anomaly are both more severe and typically present with additional symptoms beyond just low IgG levels. Severe combined immunodeficiency is a rare and severe immune disorder that would likely present with more dramatic symptoms at such a young age.

Question 15

A 1-year-old boy is evaluated for a suspected immune deficiency.He has a history since birth of eczema,recurrent rashes,and diarrhea.His white blood cell count (WBC)count is 6.75/uL (normal values: 5.0-10.8 × 103 uL)with a normal differential.Platelet count is 35,000 (normal values: 150,000-350,000/uL),and the platelets are small.His IgG is 750 mg/dL (normal values: 600-1,500 mg/dL).IgM is 30 mg/dL (normal values; 75-150 mg/dL).IgA is 475 mg/dL (normal values: 50-125 mg/dL).IgE is 750 mg/dL (10-50 mg/dL).The boy's blood is typed as O-positive,and he does not have anti-A or anti-B antibodies.Flow cytometry performed on his blood shows 11% CD19 (normal values: 5%-20%)and 50% CD3 cells (normal values: 60%-80%)with a normal ratio of CD4:CD8.T-cell function tests are abnormal.This boy most likely has:

Accepted Answer

The patient's characteristics and laboratory findings suggest Wiskott-Aldrich syndrome (WAS), an X-linked recessive disorder characterized by thrombocytopenia, eczema, recurrent infections, and immune dysregulation. The low platelet count and small platelet size are suggestive of WAS. The low IgM and elevated IgE and IgA levels are also common in WAS. The decreased number of CD19 cells and abnormal T-cell function tests further support the diagnosis of WAS. The patient's blood type and absence of anti-A and anti-B antibodies are not indicative of any specific immunodeficiency disorder. The other answer choices (Bruton's tyrosine kinase deficiency, DiGeorge anomaly, and ataxia telangiectasia) are not consistent with the patient's clinical and laboratory findings.

Question 16

A 7-month-old boy is seen by a specialist because of hypocalcemia,viral pneumonia,a history significant for recurrent diarrhea,and oral candidiasis.An x-ray reveals the lack of a thymic shadow.A likely diagnosis for this boy is:

Accepted Answer

The combination of hypocalcemia, viral pneumonia, recurrent diarrhea, and oral candidiasis along with the lack of a thymic shadow on X-ray is suggestive of DiGeorge anomaly. This is a genetic disorder characterized by the partial or complete absence of the thymus gland, leading to T-cell deficiency and increased susceptibility to infections. Other features may also be present, such as congenital heart defects, facial abnormalities, and learning difficulties. Wiskott-Aldrich syndrome, ataxia telangiectasia, and bare lymphocyte syndrome do not typically present with these symptoms and physical findings.

Question 17

A 9-month-old boy is suspected of having an immune deficiency because he had many recurrent infections with Streptococcus pneumoniae.Laboratory tests reveal a normal percentage of T cells and T-cell subsets but a lack of mature B cells and immunoglobulins.This boy most likely has:

Accepted Answer

The lack of mature B cells and immunoglobulins points to a defect in antibody production, which is characteristic of X-linked agammaglobulinemia. Wiskott-Aldrich syndrome is characterized by eczema, thrombocytopenia, and recurrent infections. DiGeorge anomaly typically presents with low T cell counts and cardiac anomalies. Chronic granulomatous disease presents with recurrent bacterial and fungal infections due to impaired phagocyte function.

Question 18

Which is true of selective IgA deficiency?

Accepted Answer

Selective IgA deficiency is not invariably fatal, nor is it very rare, and it does not mainly occur in older adults. However, patients with this condition may develop an anti-IgA antibody, which can lead to complications if they receive blood products containing IgA.

Question 19

Which of the following statements best describes common variable immunodeficiency?

Accepted Answer

Common variable immunodeficiency (CVID) is a disorder in which there are low levels of immunoglobulin A (IgA), immunoglobulin G (IgG), or both in the blood. Symptoms may not appear until adolescence or adulthood. CVID is not X-linked recessive and is not inevitably fatal.

Question 20

An autosomal-recessive disease characterized by the presence of abnormally large granules primarily affecting the function of lysosomes is known as:

Accepted Answer

The autosomal-recessive disease characterized by the presence of abnormally large granules primarily affecting the function of lysosomes is known as Chédiak-Higashi syndrome. X-linked lymphoproliferative disease is a genetic disorder affecting the immune system, leukocyte adhesion deficiency is a disorder causing impaired immunity, and common variable immunodeficiency is a syndrome causing recurring infections due to a deficiency in the immune system.

Quiz 19: Immunodeficiency Diseases