Immunology and Allergies Practice Questions

Q: Excessive crying is a known side effect following which vaccination?

DPT. **Explanation:** The correct answer is **DPT (Diphtheria, Pertussis, and Tetanus)**. **Why DPT is the correct answer:** Excessive crying (defined as persistent, inconsolable crying lasting for 3 hours or more) is a well-documented systemic adverse event following immunization (AEFI) specifically associated with the **whole-cell Pertussis (wP)** component of the DPT vaccine. This reaction typically occurs within 2–24 hours of administration. It is thought to be caused by the local inflammatory response and systemic effects of the endotoxins present in the *Bordetella pertussis* bacteria. While distressing to parents, it is usually self-limiting and not a contraindication to future doses, though acellular pertussis (aP) vaccines are associated with a significantly lower incidence of this side effect. **Why other options are incorrect:** * **Polio (OPV/IPV):** Generally very well tolerated. The most serious (though rare) side effect of OPV is Vaccine-Associated Paralytic Poliomyelitis (VAPP), not excessive crying. * **BCG:** Typically causes local reactions such as a papule, ulcer, and eventual scarring at the injection site. Systemic reactions like persistent crying are rare. * **Measles:** Common side effects include fever and a transient rash occurring 5–12 days after vaccination, rather than immediate excessive crying. **High-Yield Clinical Pearls for NEET-PG:** * **Persistent Inconsolable Crying:** Occurs in approximately 1% of children receiving the wP vaccine. * **Absolute Contraindications to Pertussis vaccine:** Encephalopathy (e.g., coma, seizures) within 7 days of a previous dose. * **Triple Response:** DPT is also associated with local pain, swelling, and redness at the injection site. * **Switching to DTaP:** If a child experiences severe reactions to DTwP, the acellular version (DTaP) is preferred for subsequent doses.

Q: What is the most common cause for the umbilical cord to not separate by the age of 2 years?

Leukocyte adhesion deficiency. **Explanation:** The normal separation of the umbilical cord typically occurs within **1 to 2 weeks** of birth. This process is mediated by **neutrophil infiltration** and the release of lysosomal enzymes, which cause the infarction and subsequent sloughing of the cord stump. **Why Leukocyte Adhesion Deficiency (LAD) is correct:** LAD (specifically Type 1) is a rare autosomal recessive primary immunodeficiency caused by a defect in the **CD18 subunit of β2-integrins**. This defect prevents leukocytes (neutrophils) from adhering to the vascular endothelium and migrating into the tissues. Because neutrophils cannot reach the umbilical site to initiate the inflammatory process required for separation, **delayed umbilical cord separation** (often beyond 3 weeks) is the classic hallmark of this condition. **Analysis of Incorrect Options:** * **Raspberry Tumor:** This is a synonym for an **Umbilical Granuloma** or occasionally a remnant of the vitellointestinal duct. It presents as a red, moist globule of tissue after the cord has already fallen off. * **Patent Urachus:** This is a failure of the urachus to obliterate, resulting in a communication between the bladder and the umbilicus. It presents with **urine leakage** from the umbilicus, not delayed cord separation. * **Umbilical Granuloma:** This is the most common cause of an umbilical mass in newborns, appearing as pink, friable tissue *after* the cord separates. It is treated with silver nitrate. **High-Yield Clinical Pearls for NEET-PG:** * **LAD Triad:** 1. Delayed separation of the umbilical cord, 2. Recurrent bacterial infections (skin/mucosa) without pus formation (cold abscesses), 3. Persistent **marked leukocytosis** (neutrophilia) even when no infection is present. * **Normal Cord Separation:** Usually occurs by 7–14 days. Separation delayed beyond **3 weeks** should trigger an investigation for LAD.

Q: Absent parathyroid, thymic aplasia with immunodeficiency and cardiac defects are features of which of the following syndromes?

Di George syndrome. **Explanation** **DiGeorge Syndrome (DGS)** is the correct answer. It is a primary immunodeficiency caused by the **maldevelopment of the 3rd and 4th pharyngeal pouches** during embryonic life. This leads to a classic triad of clinical features: 1. **Thymic Aplasia/Hypoplasia:** Results in T-cell deficiency and recurrent viral/fungal infections. 2. **Parathyroid Hypoplasia:** Leads to hypocalcemia and neonatal tetany. 3. **Conotruncal Cardiac Defects:** Most commonly Tetralogy of Fallot or Interrupted Aortic Arch. **Analysis of Incorrect Options:** * **Autoimmune Polyglandular Syndrome (APS):** A group of rare diseases characterized by autoimmune destruction of multiple endocrine glands (e.g., Addison’s disease, hypoparathyroidism, and mucocutaneous candidiasis in Type 1). It is not associated with thymic aplasia or congenital cardiac defects. * **Pendred Syndrome:** An autosomal recessive disorder characterized by sensorineural hearing loss and goiter (thyroid dysfunction). It does not involve the immune system or parathyroid glands. * **Lesch-Nyhan Syndrome:** An X-linked recessive disorder caused by a deficiency of the enzyme HGPRT. It presents with hyperuricemia, gout, and characteristic self-mutilating behavior, unrelated to the pharyngeal pouch development. **High-Yield Clinical Pearls for NEET-PG:** * **Genetics:** Most cases are due to a **22q11.2 microdeletion** (detected via FISH). * **CATCH-22 Mnemonic:** **C**ardiac defects, **A**bnormal facies, **T**hymic hypoplasia, **C**left palate, **H**ypocalcemia. * **Immunology:** Patients have low T-cell counts but normal B-cell counts (though antibody production may be impaired). * **Radiology:** Look for the **absence of a thymic shadow** on a neonatal chest X-ray.

Q: Which of the following statements regarding Bloom syndrome is true?

Decreased IgM. **Explanation:** **Bloom Syndrome** is a rare autosomal recessive disorder characterized by chromosomal instability due to a mutation in the **BLM gene** (DNA helicase). This defect leads to impaired DNA repair and a high frequency of sister chromatid exchanges. **1. Why the correct answer is right:** Patients with Bloom syndrome exhibit a progressive combined immunodeficiency. The most consistent laboratory finding is **hypogammaglobulinemia**, characterized by **decreased levels of IgG, IgA, and IgM**. While all classes are typically low, the reduction in **IgM** is a hallmark feature often tested in exams. This deficiency leads to increased susceptibility to recurrent sinopulmonary infections (otitis media and pneumonia). **2. Why the incorrect options are wrong:** * **Raised IgM (Option A):** This is characteristic of Hyper-IgM Syndrome (CD40L deficiency), not Bloom syndrome. * **Absent IgA (Option B):** While IgA is decreased in Bloom syndrome, "absent" is more characteristic of Selective IgA Deficiency. * **Raised IgE (Option C):** Elevated IgE is the hallmark of Job Syndrome (Hyper-IgE Syndrome) or Wiskott-Aldrich Syndrome, not Bloom syndrome. **3. High-Yield Clinical Pearls for NEET-PG:** * **Triad:** Telangiectatic erythema (butterfly distribution on the face), photosensitivity, and severe growth retardation (proportionate dwarfism). * **Cytogenetics:** High frequency of **Sister Chromatid Exchange (SCE)**—the "gold standard" for diagnosis. * **Malignancy:** Extremely high risk of early-onset cancers (leukemias, lymphomas, and carcinomas). * **Key Association:** "Bird-like" facies (narrow face, prominent nose).

Q: Nezelof's syndrome is characterized by recurrent episodes of which of the following conditions?

Pneumonia. **Explanation:** **Nezelof’s Syndrome** is a rare congenital immunodeficiency characterized by **isolated T-cell deficiency** despite the presence of a normal or near-normal thymus gland (unlike DiGeorge Syndrome). Because T-cells are essential for orchestrating the immune response against intracellular pathogens, these patients are highly susceptible to opportunistic infections. 1. **Why Pneumonia is Correct:** Patients with Nezelof’s Syndrome suffer from recurrent, severe sinopulmonary infections. **Pneumonia** is the most common clinical presentation, often caused by opportunistic organisms such as *Pneumocystis jirovecii*, viruses (CMV, RSV), and fungi. The lack of cell-mediated immunity prevents the body from clearing these respiratory pathogens, leading to chronic lung damage. 2. **Why Incorrect Options are Wrong:** * **Appendicitis and Cholecystitis (A & B):** These are typically acute surgical conditions related to luminal obstruction or chemical inflammation. While infections can trigger them, they are not the hallmark recurrent manifestations of primary immunodeficiencies. * **Intestinal Obstruction (C):** While these patients may suffer from chronic diarrhea or malabsorption due to intestinal infections (like Giardiasis), mechanical intestinal obstruction is not a characteristic feature of T-cell dysfunction. **Clinical Pearls for NEET-PG:** * **Triad of Nezelof’s:** Lymphopenia (T-cell), normal/hypoplastic thymus, and preserved (though often non-functional) humoral immunity. * **Differentiation:** Unlike SCID, there is some B-cell function; unlike DiGeorge, there are no parathyroid or cardiac defects (CATCH-22). * **Key Presentation:** Look for a pediatric patient with failure to thrive, chronic diarrhea, and recurrent **Pneumocystis pneumonia**.

Q: Which of the following is NOT a characteristic feature of Macrophage Activation Syndrome?

Low levels of plasma ferritin. **Explanation:** **Macrophage Activation Syndrome (MAS)** is a life-threatening complication of systemic inflammatory disorders, most commonly **Systemic Juvenile Idiopathic Arthritis (sJIA)**. It is considered a form of secondary Hemophagocytic Lymphohistiocytosis (HLH). **Why Option B is the correct answer:** In MAS, there is an extreme elevation of **plasma ferritin** (often >10,000 ng/mL). Ferritin is not just a storage protein here; it is an acute-phase reactant secreted by activated macrophages. Therefore, **low levels of plasma ferritin** are never seen in MAS; hyperferritinemia is a hallmark diagnostic criterion. **Analysis of Incorrect Options:** * **Option A:** MAS is driven by the uncontrolled proliferation and **activation of CD8+ T cells** and macrophages. These cells infiltrate organs, leading to tissue damage. * **Option C:** The pathophysiology involves a massive **cytokine storm**, specifically involving high levels of Pro-inflammatory cytokines like **IL-1, IL-6, IL-18, and IFN-gamma**, which leads to multi-organ failure. * **Option D:** MAS is clinically and pathologically indistinguishable from **secondary HLH**. While HLH is often used for genetic/familial forms, MAS is the term specifically used when it occurs in the context of autoimmune/rheumatologic diseases. **High-Yield Clinical Pearls for NEET-PG:** * **Classic Triad:** Persistent high fever, hepatosplenomegaly, and cytopenias. * **Laboratory Hallmarks:** High Ferritin, **High Triglycerides**, and **Low Fibrinogen** (due to consumption). * **Paradoxical Finding:** A sudden **drop in ESR** (due to low fibrinogen) in a previously inflamed patient is a strong red flag for MAS. * **Treatment:** High-dose corticosteroids (Methylprednisolone) and Cyclosporine; IL-1 inhibitors (Anakinra) are also effective.

Q: Antibodies to which of the following infections are NOT transmitted to a child?

Pertussis. **Explanation:** The transfer of maternal antibodies to the fetus occurs primarily via the placenta (IgG) and provides passive immunity during the first few months of life. However, the efficiency of this transfer varies significantly depending on the specific pathogen. **Why Pertussis is the correct answer:** Maternal antibodies against **Bordetella pertussis** are not efficiently transferred across the placenta. Even if the mother has high titers from previous infection or vaccination, the levels of transplacental IgG are insufficient to provide clinical protection to the neonate. This creates an "immunity gap," making infants highly vulnerable to whooping cough until they receive their own primary immunization (starting at 6 weeks). This is why the **Tdap vaccine** is specifically recommended for pregnant women during the third trimester—to maximize the temporary transfer of antibodies. **Analysis of Incorrect Options:** * **Measles:** Maternal IgG against measles is very efficiently transferred. These antibodies typically protect the infant for 6–9 months, which is why the Measles/MR vaccine is traditionally delayed until 9 months of age to avoid neutralization by maternal antibodies. * **Diphtheria & Polio:** Protective levels of antitoxins (Diphtheria) and neutralizing antibodies (Polio) are successfully transmitted to the fetus, provided the mother is immune. **High-Yield NEET-PG Pearls:** * **IgG** is the only immunoglobulin that crosses the placenta (via neonatal Fc receptors). * **Passive immunity** is strongest against Measles, Mumps, Rubella, and Tetanus. * **Poorly transmitted antibodies:** Pertussis and Hemophilus influenzae type b (Hib). * **Clinical Correlation:** Because pertussis antibodies are not naturally protective in neonates, the "cocooning strategy" (vaccinating close contacts) is often employed.

Q: Henoch-Schonlein purpura is characterized by which of the following findings, except?

Thrombocytopenia. **Explanation:** **Henoch-Schönlein Purpura (HSP)**, now commonly referred to as **IgA Vasculitis**, is the most common systemic small-vessel vasculitis in children. It is characterized by the deposition of IgA-dominant immune complexes in the walls of small vessels. **Why Thrombocytopenia is the correct answer:** The hallmark of HSP is **palpable purpura** occurring in the **absence of thrombocytopenia** or coagulopathy. In fact, the platelet count in HSP is typically **normal or even elevated** (thrombocytosis) as part of the acute phase response. If a patient presents with purpura and a low platelet count, clinicians should investigate other causes like Immune Thrombocytopenic Purpura (ITP) or leukemia. **Analysis of other options:** * **Glomerulonephritis:** Occurs in about 30-50% of cases. It typically manifests as hematuria or proteinuria due to IgA deposition in the mesangium (pathologically identical to IgA Nephropathy). * **Arthralgia:** Migratory polyarthralgia or arthritis (usually affecting knees and ankles) is seen in 75% of patients. It is non-deforming. * **Abdominal pain:** Colicky abdominal pain is common due to submucosal hemorrhage and edema. It can lead to complications like **intussusception** (typically ileo-ileal). **NEET-PG High-Yield Pearls:** * **Classic Triad:** Palpable purpura (without thrombocytopenia), arthritis, and abdominal pain. * **Most common trigger:** Upper respiratory tract infection (Group A Strep is common). * **Diagnosis:** Primarily clinical; however, skin biopsy shows **leukocytoclastic vasculitis** with IgA deposition. * **Prognosis:** Generally excellent, but long-term prognosis depends entirely on the severity of **renal involvement**.

Question 1

Excessive crying is a known side effect following which vaccination?

Accepted Answer

DPT

Answer

Polio

Answer

BCG

Answer

Measles

Question 2

What is the most common cause for the umbilical cord to not separate by the age of 2 years?

Accepted Answer

Leukocyte adhesion deficiency

Answer

Raspberry tumor

Answer

Patent urachus

Answer

Umbilical granuloma

Question 3

Absent parathyroid, thymic aplasia with immunodeficiency and cardiac defects are features of which of the following syndromes?

Accepted Answer

Di George syndrome

Answer

Autoimmune polyglandular syndrome

Answer

Pendred syndrome

Answer

Lesch-Nyhan syndrome

Question 4

A 10-year-old child presents with recurrent palpable purpura on the buttocks, arthralgias, colicky abdominal pain, diarrhea, and microscopic hematuria. What is the most likely diagnosis?

Accepted Answer

Immune complex vasculitis

Answer

Influenza

Answer

Juvenile rheumatoid arthritis

Answer

Systemic lupus erythematosus (SLE)

Question 5

Which of the following statements regarding Bloom syndrome is true?

Accepted Answer

Decreased IgM

Answer

Raised IgM

Answer

Absent IgA

Answer

Raised IgE

Question 6

DPT vaccine is contraindicated in which of the following conditions?

Accepted Answer

Evolving neurological illness

Answer

Family history of convulsions and neurological illness

Answer

Acute upper respiratory infection

Answer

Malnutrition

Question 7

Nezelof's syndrome is characterized by recurrent episodes of which of the following conditions?

Accepted Answer

Pneumonia

Answer

Appendicitis

Answer

Cholecystitis

Answer

Intestinal obstruction

Question 8

Which of the following is NOT a characteristic feature of Macrophage Activation Syndrome?

Accepted Answer

Low levels of plasma ferritin

Answer

Activation of CD8+ T cells

Answer

Presence of a cytokine storm

Answer

It is an alternative name for hemophagocytic lymphohistiocytosis

Question 9

Antibodies to which of the following infections are NOT transmitted to a child?

Accepted Answer

Pertussis

Answer

Measles

Answer

Diphtheria

Answer

Polio

Question 10

Henoch-Schonlein purpura is characterized by which of the following findings, except?

Accepted Answer

Thrombocytopenia

Answer

Glomerulonephritis

Answer

Arthralgia

Answer

Abdominal pain

Immunology and Allergies — MCQs

Immunology and Allergies — MCQs

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