Secondary Immunodeficiency Disorders — MCQs
AIDS, secondary infection will be all except
CD40 deficiency in a person signifies?
Which of the following methods is NOT recommended for the diagnosis of HIV infection in a 2-month-old child?
With the lack of CD40 in B cells, which immunological abnormality is seen?
Which of the following is not a complication of Congenital Rubella Syndrome (CRS)?
According to WHO, the major clinical sign of HIV infection in children in stage 1 is the following.
Given the immunologic abnormalities of normal serum IgG, normal serum IgA, normal serum IgM, decreased T-cell function, and decreased parathyroid function, which clinical presentation is most likely?
Best method to diagnose HIV in an infant?
What is a characteristic feature of Systemic Juvenile Idiopathic Arthritis?
A child presents with delayed separation of the umbilical cord, leukocytosis, Down syndrome, and recurrent infections. What is the most likely diagnosis?
Secondary Immunodeficiency Disorders Indian Medical PG Practice Questions and MCQs
Question 1: AIDS, secondary infection will be all except
- A. Candida
- B. Kaposi's sarcoma (Correct Answer)
- C. HSV
- D. Rubella
Explanation: ***Kaposi's sarcoma*** - Kaposi's sarcoma is a **cancer** caused by human herpesvirus 8 (HHV-8) [2] that is common in patients with AIDS, but it is a **malignancy**, not a secondary infection [2],[3]. - While it arises due to immune suppression, it represents abnormal cell proliferation rather than direct microbial invasion. *Candida* - **Candidiasis** (e.g., oral thrush, esophageal candidiasis) is a common opportunistic fungal infection in AIDS patients due to their **impaired cellular immunity** [1]. - It often presents as **white plaques** on mucous membranes and is a clear example of a secondary infection. *HSV* - **Herpes Simplex Virus (HSV)** infections, including oral and genital herpes, are common and often severe in AIDS patients. - Due to immunocompromise, these infections can be **more widespread**, chronic, or recur frequently, qualifying as secondary infections. *Rubella* - **Rubella (German measles)** is a viral infection that is generally mild and self-limiting in immunocompetent individuals. - It is **not considered an opportunistic infection** or a common secondary infection specifically associated with AIDS; rather, it is listed as a differential diagnosis for the primary HIV infection rash [1].
Question 2: CD40 deficiency in a person signifies?
- A. IgG increase
- B. T cell absent
- C. IgM increase (Correct Answer)
- D. B cell absent
Explanation: ***IgM increase*** - A deficiency in **CD40**, or its ligand **CD40L** (found on T helper cells), disrupts **T-cell-dependent B cell activation** and **class switching**. - Without proper signaling through CD40/CD40L, B cells cannot undergo **isotype switching** from **IgM** to IgG, IgA, or IgE, leading to elevated IgM levels and deficiencies in other antibody classes. *IgG increase* - **IgG levels** would likely be **decreased** in CD40 deficiency due to the impaired ability of B cells to undergo **class switching** from IgM to other antibody isotypes. - The primary role of CD40/CD40L interaction is to facilitate this class switching process. *T cell absent* - **CD40 deficiency** does not directly cause the absence of **T cells**; rather, it affects the ability of T cells to adequately activate B cells. - T-cell absence or severe dysfunction would be indicative of a different primary immunodeficiency, such as **SCID (Severe Combined Immunodeficiency)**. *B cell absent* - **CD40 deficiency** does not result in the absence of **B cells**; B cells are present but are dysfunctional in terms of antibody class switching. - Conditions like **X-linked agammaglobulinemia (XLA)** are characterized by the absence or severe deficiency of B cells.
Question 3: Which of the following methods is NOT recommended for the diagnosis of HIV infection in a 2-month-old child?
- A. Viral culture
- B. DNA-PCR
- C. P24 antigen assay
- D. HIV ELISA (Correct Answer)
Explanation: ***HIV ELISA*** - **HIV ELISA** (Enzyme-linked Immunosorbent Assay) detects **HIV antibodies**, which are maternally derived and can persist in newborns for up to 18 months, leading to **false positive** results. - Therefore, antibody-based tests are **not suitable** for diagnosing HIV infection in infants under 18 months of age. *Viral culture* - **HIV viral culture** can directly detect the presence of replication-competent virus in an infant's blood. - While sensitive, it is **expensive**, labor-intensive, and takes a long time (several weeks) to obtain results, making it less practical for routine diagnosis. *DNA-PCR* - **DNA PCR (Polymerase Chain Reaction)** directly detects **HIV proviral DNA** within infected cells, making it highly specific and sensitive for early infant diagnosis. - It is currently the **recommended method** for HIV diagnosis in infants and young children, especially in the first few months of life. *P24 antigen assay* - The **P24 antigen assay** detects the **core protein of the HIV virus**, indicating active viral replication. - It can be used for early diagnosis in infants but may be less sensitive than DNA PCR, particularly in the presence of maternal antibodies or during early infection.
Question 4: With the lack of CD40 in B cells, which immunological abnormality is seen?
- A. Total lack of NK cells
- B. Lack of CD8 mediated cytotoxicity
- C. Inability of neutrophil against infections
- D. Decreased IgG and increase in IgM (Correct Answer)
Explanation: ***Decreased IgG and increase in IgM*** - The interaction between **CD40 on B cells** and **CD40L (CD154) on T helper cells** is crucial for **B cell activation**, proliferation, and **class switch recombination** (CSR). - Without this interaction, B cells cannot undergo CSR, leading to a failure to produce **IgG, IgA, or IgE**, while **IgM levels remain high** because IgM production is the initial default. *Total lack of NK cells* - **Natural Killer (NK) cells** are part of the innate immune system and their development is largely independent of CD40-CD40L signaling. - The absence of CD40 on B cells primarily affects adaptive humoral immunity, not NK cell numbers or function. *Lack of CD8 mediated cytotoxicity* - **CD8+ T cells** mediate cytotoxicity against infected or cancerous cells and their activation is primarily dependent on antigen presentation by **MHC class I molecules** and costimulation, not directly on B cell CD40. - While B cells can act as APCs, their CD40 interaction is more critical for T helper cell help for humoral responses. *Inability of neutrophil against infections* - **Neutrophils** are phagocytic cells important in innate immunity, and their function is largely independent of CD40 on B cells. - Neutrophil activity relies on pathogen recognition, phagocytosis, and degranulation, which are not directly regulated by the B cell CD40-CD40L pathway.
Question 5: Which of the following is not a complication of Congenital Rubella Syndrome (CRS)?
- A. Retinopathy
- B. Cardiac abnormalities
- C. Macrocephaly (Correct Answer)
- D. Spontaneous abortion
Explanation: ***Macrocephaly*** - While CRS can lead to various neurological complications, **macrocephaly** (abnormally large head circumference) is not a typical manifestation of the syndrome. Neurological issues in CRS more commonly involve **microcephaly** due to brain damage. - Other common neurological complications include **meningoencephalitis** and developmental delays, but not an enlarged head. *Retinopathy* - **Pigmentary retinopathy** (salt-and-pepper retinopathy) is a classic ocular manifestation of CRS, often present at birth. - This is a direct consequence of the rubella virus affecting the developing retinal structures. *Spontaneous abortion* - Maternal rubella infection, especially during the **first trimester**, carries a significant risk of **spontaneous abortion** due to severe fetal damage. - The virus's teratogenic effects can be so profound that the fetus is not viable. *Cardiac abnormalities* - **Congenital heart defects** are a hallmark of CRS, with **patent ductus arteriosus (PDA)** and **pulmonary artery stenosis** being the most common. - These abnormalities result from the rubella virus interfering with normal cardiac development during embryogenesis.
Question 6: According to WHO, the major clinical sign of HIV infection in children in stage 1 is the following.
- A. Not gaining weight
- B. Generalised lymphadenopathy (Correct Answer)
- C. Oral candidiasis
- D. None of the options
Explanation: ***Generalised lymphadenopathy*** - According to WHO staging for HIV infection in children, **persistent generalized lymphadenopathy (PGL)** is a major clinical sign in Stage 1. - This stage is characterized by asymptomatic or mild clinical manifestations, with PGL being one of the key visible indicators. - PGL is defined as enlarged lymph nodes (>1 cm) in two or more non-contiguous sites, excluding inguinal nodes. *Not gaining weight* - **Failure to thrive** or **unexplained moderate malnutrition** typically falls under WHO clinical Stage 2 or 3, not Stage 1. - While weight loss can occur in HIV, it usually signifies more advanced disease progression in children. *Oral candidiasis* - **Oral candidiasis** in children with HIV usually indicates more advanced disease and is classified under **WHO clinical Stage 2 or 3**, depending on its persistence and severity. - It suggests a compromised immune system beyond the earliest stages of HIV infection. *None of the options* - This option is incorrect because **generalized lymphadenopathy** is indeed a major clinical sign of HIV infection in children in Stage 1, according to WHO criteria. - The other options provided represent signs found in later stages of HIV disease in children.
Question 7: Given the immunologic abnormalities of normal serum IgG, normal serum IgA, normal serum IgM, decreased T-cell function, and decreased parathyroid function, which clinical presentation is most likely?
- A. A 1-year-old boy with severe eczema, recurrent middle-ear infections, lymphopenia, and thrombocytopenia
- B. A 9-year-old boy with an eczema-like rash and recurrent severe staphylococcal infections
- C. A 5-year-old boy who, after 3 months of age, developed recurrent otitis media, pneumonia, diarrhea, and sinusitis, often with simultaneous infections at two or more disparate sites
- D. A distinctive-appearing 8-month-old boy with an interrupted aortic arch, hypocalcemia, and cleft palate (Correct Answer)
Explanation: ***A distinctive-appearing 8-month-old boy with an interrupted aortic arch, hypocalcemia, and cleft palate*** - This presentation is highly suggestive of **DiGeorge syndrome**, characterized by **thymic hypoplasia** (leading to decreased T-cell function) and **parathyroid hypoplasia** (causing hypocalcemia). - **Cardiac defects** (like an interrupted aortic arch) and **facial anomalies** (including cleft palate) are also classic features of this disorder, which involves a deletion on chromosome 22q11.2. *A 1-year-old boy with severe eczema, recurrent middle-ear infections, lymphopenia, and thrombocytopenia* - This clinical picture describes **Wiskott-Aldrich syndrome**, an X-linked disorder characterized by the triad of eczema, thrombocytopenia (with small platelets), and immunodeficiency leading to recurrent infections. - While it involves immunodeficiency and lymphopenia, it does not typically present with decreased parathyroid function. *A 9-year-old boy with an eczema-like rash and recurrent severe staphylococcal infections* - This presentation is characteristic of **hyper-IgE syndrome** (Job's syndrome), an immunodeficiency characterized by extremely elevated IgE levels, recurrent staphylococcal skin infections, and eczema. - The immunologic abnormalities described in the stem (normal Ig levels, decreased T-cell function, decreased parathyroid function) do not match the key features of hyper-IgE syndrome. *A 5-year-old boy who, after 3 months of age, developed recurrent otitis media, pneumonia, diarrhea, and sinusitis, often with simultaneous infections at two or more disparate sites* - This description is consistent with **X-linked agammaglobulinemia (XLA)**, where B-cell maturation is blocked, leading to a profound deficiency of all immunoglobulin classes. - The stem mentions normal serum IgG, IgA, and IgM, which rules out XLA.
Question 8: Best method to diagnose HIV in an infant?
- A. ELISA
- B. PCR (Correct Answer)
- C. Western blot
- D. All of the options
Explanation: ***PCR*** - **Polymerase Chain Reaction (PCR)** detects **HIV nucleic acids** (DNA or RNA) directly, which is crucial for infants because maternal antibodies can persist for up to 18 months, interfering with antibody-based tests. - PCR allows for early diagnosis, often within the first few weeks or months of life, facilitating timely intervention. *ELISA* - **Enzyme-linked immunosorbent assay (ELISA)** detects HIV antibodies. - In infants, ELISA can be misleading due to the presence of **maternal HIV antibodies** transferred across the placenta, making it unreliable for diagnosing active infection. *Western blot* - **Western blot** is used to confirm positive ELISA results in adults by detecting specific HIV proteins. - Like ELISA, it relies on the detection of **antibodies** and is therefore not reliable in infants due to maternally transmitted antibodies. *All of the options* - This option is incorrect because **ELISA** and **Western blot** are antibody-based tests that are unreliable in infants due to the presence of **maternal antibodies**. - Only **PCR** directly detects the virus itself, making it the preferred diagnostic method in this age group.
Question 9: What is a characteristic feature of Systemic Juvenile Idiopathic Arthritis?
- A. Uveitis is a feature
- B. It occurs after 16 years of age
- C. NSAIDs are contraindicated
- D. RA factor is negative (Correct Answer)
Explanation: ### Explanation **Systemic Juvenile Idiopathic Arthritis (sJIA)**, also known as Still’s disease, is a unique subtype of JIA characterized by prominent extra-articular features. **Why the correct answer is right:** In sJIA, the **Rheumatoid Factor (RF) is characteristically negative**. Unlike the polyarticular subtype (which can be RF positive), sJIA is considered an autoinflammatory disease rather than a classic autoimmune disease. Diagnosis is clinical, based on the presence of arthritis in one or more joints associated with (or preceded by) a fever of at least 2 weeks' duration that is daily ("quotidian") for at least 3 days, accompanied by features like an evanescent salmon-pink rash, lymphadenopathy, or serositis. **Analysis of Incorrect Options:** * **A. Uveitis is a feature:** This is incorrect for sJIA. Chronic anterior uveitis is a classic complication of **Oligoarticular JIA** (especially if ANA positive). Uveitis is very rare in the systemic subtype. * **B. It occurs after 16 years of age:** By definition, JIA must have an onset **before the age of 16**. If similar symptoms occur after 16, it is termed Adult-Onset Still’s Disease (AOSD). * **C. NSAIDs are contraindicated:** This is false. NSAIDs are often the **first-line** symptomatic treatment for pain and fever in JIA, though systemic steroids or biologics (IL-1 and IL-6 inhibitors) are usually required for definitive control. **High-Yield Clinical Pearls for NEET-PG:** * **Fever Pattern:** Classic "Quotidian" fever (spikes once daily, usually in the evening, returning to baseline). * **Laboratory Markers:** Marked leukocytosis, thrombocytosis, and highly elevated ESR/CRP. * **Ferritin:** Extremely high ferritin levels are common and can signal the onset of **Macrophage Activation Syndrome (MAS)**, a life-threatening complication of sJIA. * **Biologics of Choice:** Tocilizumab (IL-6 inhibitor) and Anakinra/Canakinumab (IL-1 inhibitors).
Question 10: A child presents with delayed separation of the umbilical cord, leukocytosis, Down syndrome, and recurrent infections. What is the most likely diagnosis?
- A. Leukocyte Adhesion Deficiency (Correct Answer)
- B. Neonatal Sepsis
- C. Histiocytosis-X
- D. All of the above
Explanation: ### Explanation **Correct Option: A. Leukocyte Adhesion Deficiency (LAD)** **Why it is correct:** Leukocyte Adhesion Deficiency (Type 1) is a primary immunodeficiency caused by a defect in the **CD18 subunit of $\beta_2$-integrins**. This defect prevents neutrophils from adhering to the vascular endothelium and migrating into tissues (diapedesis). * **Delayed separation of the umbilical cord:** This is the classic hallmark of LAD. Normally, neutrophils infiltrate the cord stump to facilitate its detachment; in LAD, the absence of neutrophils at the site leads to delayed separation (often >30 days). * **Leukocytosis:** Because neutrophils cannot leave the bloodstream to enter tissues, they accumulate in the blood, leading to persistent, marked neutrophilic leukocytosis. * **Recurrent Infections:** Patients suffer from skin and mucosal infections (e.g., omphalitis, periodontitis) characterized by a **lack of pus formation** despite high white cell counts. * **Association:** While not a primary feature, LAD has been documented in case reports involving children with Down syndrome. **Why other options are incorrect:** * **B. Neonatal Sepsis:** While sepsis causes leukocytosis and infections, it does not explain the specific anatomical delay in umbilical cord separation. * **C. Histiocytosis-X (Langerhans Cell Histiocytosis):** This typically presents with seborrheic-like skin rashes, lytic bone lesions, and hepatosplenomegaly, rather than a specific defect in cord separation or integrin function. **High-Yield Clinical Pearls for NEET-PG:** * **LAD Type 1:** Defect in **CD18** (Integrins). * **LAD Type 2:** Defect in **Sialyl-Lewis X** (Selectins); presents with short stature and intellectual disability. * **Key Triad:** Delayed cord separation + Recurrent "cold" infections (no pus) + Extreme neutrophilia. * **Diagnosis:** Confirmed by **Flow Cytometry** showing decreased expression of CD11/CD18.
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