Immunology and Allergies Practice Questions

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: A 5-year-old child presents with non-blanching purpura over the buttocks and lower limbs along with colicky abdominal pain. Further evaluation revealed deposition of IgA immune complexes. What is the most likely diagnosis?

Henoch-Schonlein Purpura. **Explanation:** The clinical presentation of non-blanching purpura (palpable purpura) [2] localized to the buttocks and lower limbs, combined with colicky abdominal pain in a child, is the classic triad of **Henoch-Schönlein Purpura (HSP)** [1], now also known as **IgA Vasculitis**. [1] **1. Why Option A is Correct:** HSP is a small-vessel vasculitis characterized by the deposition of **IgA-dominant immune complexes** in the vessel walls. [1] It typically follows an upper respiratory tract infection. The hallmark features include: * **Skin:** Palpable purpura (gravity-dependent distribution). [2] * **GI:** Colicky pain, vomiting, or GI bleeding (due to bowel wall edema). [1] * **Joints:** Migratory arthralgia/arthritis. * **Renal:** IgA nephropathy (hematuria). **2. Why Other Options are Incorrect:** * **Kawasaki Disease:** A medium-vessel vasculitis in children characterized by high fever, conjunctivitis, strawberry tongue, and coronary artery aneurysms. [2] It does not present with IgA deposition or typical purpura. * **Wegener’s Granulomatosis (GPA):** A small-vessel vasculitis associated with **c-ANCA** and granulomatous inflammation of the respiratory tract and kidneys. It is rare in young children. * **Takayasu Disease:** A large-vessel vasculitis ("pulseless disease") affecting the aorta and its branches, typically seen in young females. **3. NEET-PG High-Yield Pearls:** * **Most common** systemic vasculitis in children. * **Biopsy Findings:** Leukocytoclastic vasculitis with IgA and C3 deposition on immunofluorescence. * **Platelet Count:** Normal (distinguishes it from ITP). * **Complication:** Intussusception (usually ileo-ileal) is a known surgical complication in these patients. * **Management:** Mostly supportive; steroids are used for severe GI or renal involvement.

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**.

Q: In a 5-year-old boy with a history of recurrent pyogenic infections by bacteria with polysaccharide-rich capsules, which of the following investigations should be done?

IgA and IgG2 deficiency. **Explanation:** The correct answer is **D. IgA and IgG2 deficiency.** **Medical Concept:** The immune response to **encapsulated bacteria** (such as *Streptococcus pneumoniae*, *Haemophilus influenzae* type b, and *Neisseria meningitidis*) relies heavily on the production of antibodies against their **polysaccharide-rich capsules**. In humans, the antibody response to polysaccharide antigens is primarily mediated by the **IgG2 subclass**. Clinically, isolated IgG2 deficiency is rare; it most commonly occurs in association with **Selective IgA deficiency**. This combined deficiency significantly impairs the body's ability to opsonize and clear encapsulated organisms, leading to recurrent sinopulmonary and pyogenic infections. **Analysis of Options:** * **Option A (IgA deficiency):** While IgA deficiency is the most common primary immunodeficiency, it is often asymptomatic. Recurrent pyogenic infections specifically by encapsulated bacteria point more strongly toward a defect in the IgG subclass responsible for polysaccharide antigens. * **Option B (IgG1 deficiency):** IgG1 is the most abundant subclass and primarily responds to protein antigens (e.g., toxoids). Deficiency usually leads to a decrease in total IgG levels. * **Option C (IgG2 deficiency):** While IgG2 deficiency explains the susceptibility to encapsulated bacteria, it is frequently associated with IgA deficiency in clinical practice, making Option D the more comprehensive and clinically accurate choice. **High-Yield Pearls for NEET-PG:** * **IgG1 & IgG3:** Respond to **protein** antigens (e.g., viral proteins, tetanus toxoid). * **IgG2 & IgG4:** Respond to **polysaccharide** antigens. * **Selective IgA Deficiency:** Patients are at risk of **anaphylaxis** during blood transfusions due to anti-IgA antibodies. * **Wiskott-Aldrich Syndrome:** Another high-yield condition featuring low IgM and poor response to polysaccharide antigens.

Q: Which of the following conditions is treated with Intravenous Immunoglobulin (IVIG)?

Kawasaki disease, Bruton's disease, Guillain-Barré syndrome. **Explanation:** Intravenous Immunoglobulin (IVIG) is a blood product containing pooled IgG antibodies from thousands of donors. It functions through multiple mechanisms: providing passive immunity in immunodeficiency and exerting anti-inflammatory/immunomodulatory effects in autoimmune and neurological disorders. **Why Option B is Correct:** * **Kawasaki Disease:** IVIG is the gold standard treatment (along with Aspirin) to prevent coronary artery aneurysms. It reduces systemic inflammation by neutralizing bacterial superantigens and inhibiting cytokine production. * **Bruton’s Agammaglobulinemia (X-linked Agammaglobulinemia):** Since these patients lack B-cells and cannot produce their own antibodies, lifelong IVIG replacement is essential to prevent recurrent pyogenic infections. * **Guillain-Barré Syndrome (GBS):** IVIG acts as an immunomodulator that neutralizes pathogenic autoantibodies attacking the peripheral nerves, accelerating recovery. **Why Other Options are Incorrect:** * **Wegener’s Granulomatosis (Granulomatosis with Polyangiitis) & Polyarteritis Nodosa (PAN):** These are systemic vasculitides primarily managed with **Corticosteroids** and cytotoxic agents like **Cyclophosphamide** or Rituximab. While IVIG is occasionally used in refractory cases, it is not the primary or standard treatment. Options A, C, and D are incorrect because they include these conditions as primary indications. **NEET-PG High-Yield Pearls:** * **Kawasaki Dose:** 2 g/kg as a single infusion. Most effective if given within the first 10 days of fever. * **ITP Connection:** IVIG is also a first-line treatment for acute Immune Thrombocytopenic Purpura (ITP) to rapidly increase platelet counts by blocking Fc receptors on splenic macrophages. * **Contraindication:** IVIG is contraindicated in patients with **Selective IgA deficiency** due to the risk of anaphylaxis (anti-IgA antibodies).

Q: All of the following are true about Wiskott-Aldrich syndrome except:

Large size platelets. **Explanation:** Wiskott-Aldrich Syndrome (WAS) is an X-linked recessive disorder caused by a mutation in the **WASp gene**, which is critical for actin cytoskeleton remodeling in hematopoietic cells. **Why Option C is the correct answer (The Exception):** In WAS, the hallmark hematological finding is **microthrombocytopenia**. Patients have a low platelet count and, characteristically, **small-sized platelets**. Finding large platelets (megathrombocytes) would instead point toward conditions like Bernard-Soulier Syndrome or ITP. **Analysis of Incorrect Options (True statements about WAS):** * **A. Bloody diarrhea:** This is often the earliest clinical manifestation in infancy due to severe thrombocytopenia and platelet dysfunction. * **B. Immunoglobulin profile:** The classic pattern is **low IgM**, normal to low IgG, and **elevated IgA and IgE**. This imbalance contributes to the underlying immunodeficiency. * **D. Atopic dermatitis:** Eczema is a core component of the clinical triad and is typically severe and difficult to manage. **Clinical Pearls for NEET-PG:** * **The Classic Triad:** 1. Thrombocytopenia (Microplatelets), 2. Eczema, 3. Recurrent Infections (especially encapsulated organisms like *S. pneumoniae*). * **Mnemonic:** **TIE** (Thrombocytopenia, Infections, Eczema). * **Inheritance:** X-linked Recessive (affects males). * **Complications:** High risk of **Non-Hodgkin Lymphoma** and autoimmune hemolytic anemia. * **Definitive Treatment:** Hematopoietic stem cell transplant (HSCT).

Q: Which of the following are true about Henoch-Schönlein purpura (HSP)?

Palpable purpura and Kidneys commonly affected. **Explanation:** Henoch-Schönlein Purpura (HSP), now commonly referred to as **IgA Vasculitis**, is the most common systemic vasculitis in children. It is a small-vessel vasculitis characterized by the deposition of **IgA-dominant immune complexes**. **Why Option D is Correct:** The classic clinical tetrad of HSP includes **palpable purpura** (without thrombocytopenia), arthritis/arthralgia, abdominal pain, and **renal involvement**. Renal involvement (HSP Nephritis) occurs in approximately 30-50% of patients and is a major determinant of long-term prognosis. It typically manifests as hematuria or proteinuria. **Analysis of Incorrect Options:** * **Option A:** HSP is an immune-complex-mediated vasculitis, not a Pauci-immune vasculitis. **C-ANCA** is specifically associated with Granulomatosis with Polyangiitis (Wegener's), not HSP. * **Option B:** While palpable purpura is the hallmark sign, this option is incomplete compared to Option D, as renal involvement is a critical systemic feature of the disease. * **Option C:** This is a common distractor. In HSP, the purpura is **non-thrombocytopenic**. The platelet count is typically normal or even elevated (as an acute phase reactant). If a patient has purpura with a low platelet count, the diagnosis is more likely Immune Thrombocytopenic Purpura (ITP). **High-Yield Clinical Pearls for NEET-PG:** * **Trigger:** Often follows an Upper Respiratory Tract Infection (URTI). * **Biopsy:** Skin biopsy shows **Leukocytoclastic vasculitis** with IgA deposition on immunofluorescence. * **Gastrointestinal:** Can lead to **Intussusception** (characteristically ileo-ileal). * **Treatment:** Mainly supportive; steroids are used for severe GI symptoms or renal involvement but do not prevent chronic kidney disease.

Q: Which of the following is not typically seen in Henoch-Schonlein purpura?

Thrombocytopenia. **Explanation:** Henoch-Schönlein Purpura (HSP), now commonly referred to as **IgA Vasculitis**, is a small-vessel vasculitis characterized by the deposition of immune complexes containing **Immunoglobulin A (IgA)** [1]. **Why Thrombocytopenia is the correct answer:** The hallmark of HSP is **non-thrombocytopenic purpura**. Unlike conditions like ITP or TTP where bruising occurs due to low platelet counts, the purpura in HSP is caused by inflammation of the blood vessel walls (leukocytoclastic vasculitis) leading to extravasation of RBCs. Therefore, the **platelet count in HSP is typically normal or even elevated** (as an acute-phase reactant). Finding thrombocytopenia should prompt a clinician to look for alternative diagnoses. **Why the other options are incorrect:** * **Glomerulonephritis (B):** Renal involvement occurs in about 40-50% of cases, presenting as hematuria or proteinuria. It is histologically identical to IgA Nephropathy (Berger’s disease). * **Arthralgia (C):** Migratory polyarthralgia, typically affecting the knees and ankles, is seen in ~75% of patients. It is non-deforming. * **Abdominal pain (D):** Colicky abdominal pain due to bowel wall edema and hemorrhage is common [1]. It can lead to complications like **intussusception** (typically ileo-ileal). **High-Yield Clinical Pearls for NEET-PG:** * **Classic Tetrad:** Palpable purpura (without thrombocytopenia), arthritis/arthralgia, abdominal pain, and renal disease. * **Demographics:** Most common vasculitis in children; often follows an Upper Respiratory Tract Infection (URTI). * **Diagnosis:** Primarily clinical. Biopsy shows **IgA deposition** on immunofluorescence. * **Treatment:** Mostly supportive; steroids are used for severe gastrointestinal or renal involvement.

Question 1

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 2

Which of the following statements regarding Bloom syndrome is true?

Accepted Answer

Decreased IgM

Answer

Raised IgM

Answer

Absent IgA

Answer

Raised IgE

Question 3

A 5-year-old child presents with non-blanching purpura over the buttocks and lower limbs along with colicky abdominal pain. Further evaluation revealed deposition of IgA immune complexes. What is the most likely diagnosis?

Accepted Answer

Henoch-Schonlein Purpura

Answer

Kawasaki Disease

Answer

Wegener's Granulomatosis

Answer

Takayasu Disease

Question 4

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

Accepted Answer

Pertussis

Answer

Measles

Answer

Diphtheria

Answer

Polio

Question 5

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

Accepted Answer

Thrombocytopenia

Answer

Glomerulonephritis

Answer

Arthralgia

Answer

Abdominal pain

Question 6

In a 5-year-old boy with a history of recurrent pyogenic infections by bacteria with polysaccharide-rich capsules, which of the following investigations should be done?

Accepted Answer

IgA and IgG2 deficiency

Answer

IgA deficiency

Answer

IgG1 deficiency

Answer

IgG2 deficiency

Question 7

Which of the following conditions is treated with Intravenous Immunoglobulin (IVIG)?

Accepted Answer

Kawasaki disease, Bruton's disease, Guillain-Barré syndrome

Answer

Kawasaki disease, Polyarteritis nodosa, Wegener's granulomatosis

Answer

Wegener's granulomatosis, Bruton's disease, Guillain-Barré syndrome

Answer

Kawasaki disease, Wegener's granulomatosis, Bruton's disease

Question 8

All of the following are true about Wiskott-Aldrich syndrome except:

Accepted Answer

Large size platelets

Answer

Bloody diarrhea during infancy

Answer

Low IgM and elevated IgA and IgE

Answer

Atopic dermatitis

Question 9

Which of the following are true about Henoch-Schönlein purpura (HSP)?

Accepted Answer

Palpable purpura and Kidneys commonly affected

Answer

Palpable purpura and C-ANCA positivity

Answer

Palpable purpura

Answer

Palpable purpura and Thrombocytopenia

Question 10

Which of the following is not typically seen in Henoch-Schonlein purpura?

Accepted Answer

Thrombocytopenia

Answer

Glomerulonephritis

Answer

Arthralgia

Answer

Abdominal pain

Immunology and Allergies — MCQs

Immunology and Allergies — MCQs

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