Immunology and Allergies Practice Questions

Q: Which one of the following is not a feature of DiGeorge syndrome?

Rocker bottom feet. **Explanation:** DiGeorge syndrome (22q11.2 deletion syndrome) is a primary immunodeficiency caused by the abnormal development of the **third and fourth pharyngeal pouches**. This results in a classic constellation of symptoms often remembered by the mnemonic **CATCH-22**. **Why "Rocker bottom feet" is the correct answer:** Rocker bottom feet (congenital vertical talus) is a classic dysmorphic feature associated with **Trisomy 18 (Edwards syndrome)** and **Trisomy 13 (Patau syndrome)**, but it is not a characteristic feature of DiGeorge syndrome. **Analysis of incorrect options:** * **A. Congenital heart defects:** These are present in ~75% of cases, most commonly **Conotruncal anomalies** such as Tetralogy of Fallot, Interrupted aortic arch, and Truncus arteriosus. * **B. Abnormalities of palate:** Velopharyngeal insufficiency and **Cleft palate** are common due to the maldevelopment of the pharyngeal arches. * **C. Hypocalcemia:** This occurs due to **Parathyroid hypoplasia/aplasia**. It typically presents as neonatal seizures or tetany in the first few days of life. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic CATCH-22:** **C**ardiac defects, **A**bnormal facies (low-set ears, hypertelorism), **T**hymic hypoplasia (leading to T-cell deficiency/infections), **C**left palate, **H**ypocalcemia, and **22**q11.2 deletion. * **Chest X-ray:** Look for the **absence of a thymic shadow** (also seen in SCID). * **Diagnosis:** Confirmed via **FISH** (Fluorescence In Situ Hybridization) or MLPA. * **Management:** Avoid live vaccines if T-cell count is low; irradiated blood products are preferred to prevent Graft-vs-Host Disease.

Q: A 1-year-old boy presents with a history of recurrent pneumonia, eczema, and prolonged bleeding after circumcision. A peripheral smear shows thrombocytopenia with small platelets. Which of the following is most likely to be deficient?

IgM. ### Explanation The clinical triad of **recurrent infections (pneumonia), eczema, and thrombocytopenia with small platelets (microthrombocytes)** is pathognomonic for **Wiskott-Aldrich Syndrome (WAS)**. This is an X-linked recessive disorder caused by a mutation in the *WASP* gene, which affects the actin cytoskeleton of hematopoietic cells. **Why IgM is the correct answer:** In Wiskott-Aldrich Syndrome, the characteristic immunoglobulin pattern is: * **Low IgM:** This is the most consistent finding and leads to an increased susceptibility to polysaccharide-encapsulated bacteria (e.g., *S. pneumoniae*, *H. influenzae*). * **Normal to Low IgG.** * **Elevated IgA and IgE.** **Analysis of Incorrect Options:** * **Option A (IgA):** In WAS, IgA levels are typically **elevated**, not deficient. Isolated IgA deficiency presents with mucosal infections and anaphylaxis during blood transfusions, but not with thrombocytopenia or eczema. * **Option B (IgE):** IgE levels are typically **elevated** in WAS, contributing to the severe atopic dermatitis (eczema) seen in these patients. * **Option D (IgG):** IgG levels are usually normal or only slightly decreased. A primary IgG deficiency (like CVID) would cause recurrent infections but would not explain the small platelets or eczema. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for WAS:** **TIE** (Thrombocytopenia, Infections, Eczema). * **Platelet Morphology:** WAS is the *only* condition characterized by **microthrombocytes** (small platelets). In contrast, ITP or Bernard-Soulier syndrome features large platelets. * **Genetics:** X-linked recessive; mutation in the **WASP gene** (presents on the short arm of the X chromosome). * **Complications:** Increased risk of autoimmune diseases and B-cell lymphomas. * **Definitive Treatment:** Hematopoietic stem cell transplant.

Q: A 5-month-old boy presented with spontaneous nosebleeds and bloody diarrhea. He also has a history of recurrent chest and ear infections requiring frequent hospitalizations. On examination, the child had atopic dermatitis and petechiae all over the body. Laboratory findings suggested an abnormally low platelet count along with eosinophilia. Which of the following statements is NOT true about this condition?

Low IgM and IgG levels.. ### **Explanation** The clinical presentation of **thrombocytopenia** (petechiae, nosebleeds), **eczema** (atopic dermatitis), and **recurrent infections** in a male infant is the classic triad of **Wiskott-Aldrich Syndrome (WAS)**. This is an X-linked recessive disorder caused by a mutation in the *WASP* gene, which affects the actin cytoskeleton in hematopoietic cells. #### **Why Option B is the Correct Answer (The "NOT True" Statement)** In Wiskott-Aldrich Syndrome, the characteristic immunoglobulin pattern is: * **Low IgM** * **Normal to Low IgG** * **High IgA and High IgE** Option B states that both IgM and IgG are low; however, the hallmark of WAS is specifically a **low IgM** level. #### **Analysis of Other Options** * **Option A:** True. WAS involves a combined immunodeficiency. There is a progressive depletion of T-cells in the peripheral blood and paracortical areas of lymph nodes, leading to impaired cellular immunity. * **Option C:** True. Serum IgA and IgE levels are typically elevated in these patients. Eosinophilia (mentioned in the stem) is also a common finding. * **Option D:** True. Patients with WAS have a significantly increased risk of developing autoimmune diseases and malignancies, particularly **B-cell lymphomas** (often EBV-associated). #### **NEET-PG High-Yield Pearls** * **Mnemonic (TIE):** **T**hrombocytopenia, **I**mmunodeficiency, **E**czema. * **Platelet Morphology:** WAS is unique because it features **microthrombocytes** (abnormally small platelets). This is a high-yield diagnostic clue. * **Genetics:** X-linked recessive; *WASP* gene (Xp11.22). * **Defect:** Failure of actin polymerization, affecting leukocyte migration and immune synapse formation. * **Treatment:** Hematopoietic stem cell transplant (HSCT) is the definitive cure.

Q: An 8-month-old boy with a history of recurrent pneumonia is found to have almost no circulating IgG. Cellular immunity is normal. His brother had this same disease and died of echovirus encephalitis. His parents and sisters have normal serum levels of IgG. What is the appropriate diagnosis?

X-linked agammaglobulinemia of Bruton. ### Explanation **Correct Option: D. X-linked agammaglobulinemia (XLA) of Bruton** **Why it is correct:** XLA is caused by a mutation in the **Bruton Tyrosine Kinase (BTK) gene**, which is essential for B-cell maturation. Without BTK, pre-B cells cannot develop into mature B cells, leading to a near-total absence of all immunoglobulin classes (IgG, IgA, IgM). * **Clinical Presentation:** Symptoms typically appear after 6 months of age (as maternal IgG wanes) with recurrent sinopulmonary infections caused by encapsulated bacteria (*S. pneumoniae, H. influenzae*). * **Key Clue:** Susceptibility to **Enteroviruses** (like Echovirus and Poliovirus) is a classic hallmark of XLA, often leading to fatal encephalitis or chronic meningitis. * **Inheritance:** It is X-linked recessive, explaining why only male siblings are affected while parents and sisters are healthy. **Why other options are incorrect:** * **A. DiGeorge Syndrome:** This is a defect in **T-cell (cellular) immunity** due to thymic hypoplasia. The question states cellular immunity is normal. * **B. Isolated IgA Deficiency:** This is the most common primary immunodeficiency. While patients have low IgA, their **IgG levels are normal**, and they do not typically present with severe agammaglobulinemia or fatal echovirus infections. * **C. Wiskott-Aldrich Syndrome:** Characterized by the triad of **Eczema, Thrombocytopenia (small platelets), and Immunodeficiency**. It involves both B and T cell dysfunction, not isolated IgG absence. **NEET-PG High-Yield Pearls:** * **Flow Cytometry:** Shows absent or <2% CD19+ and CD20+ B cells. * **Physical Exam:** Characterized by **absent or hypoplastic tonsils** and lymph nodes (due to lack of germinal centers). * **Treatment:** Lifelong Intravenous Immunoglobulin (IVIG) replacement. Live vaccines (like OPV) are strictly contraindicated.

Q: Eye involvement is seen in which of the following subtypes of Juvenile Rheumatoid Arthritis?

Seronegative pauciarticular JRA, early onset. ### Explanation The correct answer is **D. Seronegative pauciarticular JRA, early onset.** **1. Why the Correct Answer is Right:** Juvenile Idiopathic Arthritis (JIA), formerly known as JRA, is classified based on the number of joints involved and the presence of biomarkers. **Pauciarticular (Oligoarticular) JIA** involves $\le$ 4 joints. The **early-onset subtype** (typically girls < 5 years old) is strongly associated with **positive Antinuclear Antibody (ANA)** and a high risk of **chronic asymptomatic iridocyclitis (anterior uveitis)**. Because the eye involvement is often "silent" (painless and non-red), regular slit-lamp examinations are mandatory to prevent blindness. **2. Why the Other Options are Wrong:** * **A & B (Late-onset Pauciarticular):** This subtype typically affects older boys (> 8 years) and is often associated with **HLA-B27**. It frequently involves the lower limbs and may progress to Ankylosing Spondylitis. While eye involvement (acute uveitis) can occur, it is symptomatic (painful, red eye), unlike the classic "silent" involvement of the early-onset type. * **C (Polyarticular JRA):** This involves $\ge$ 5 joints. While uveitis can occur in the seronegative polyarticular form, the risk is significantly lower (approx. 5%) compared to the early-onset pauciarticular group (approx. 20-30%). **3. NEET-PG High-Yield Pearls:** * **ANA Positivity:** The single best predictor for the development of uveitis in JIA. * **Systemic JIA (Still’s Disease):** Characterized by evanescent salmon-pink rashes and quotidian fever; notably, it is **least likely** to have uveitis. * **Screening:** Children with ANA+ oligoarticular JIA require slit-lamp exams every 3 months. * **RF Positivity:** Seropositive polyarticular JIA (RF+) mimics adult Rheumatoid Arthritis and has a poorer joint prognosis but lower risk of uveitis.

Q: Which of the following is true regarding ataxia telangiectasia?

It is an autosomal recessive disorder.. **Ataxia-Telangiectasia (A-T)** is a complex multisystem neurodegenerative disorder caused by mutations in the **ATM (Ataxia-Telangiectasia Mutated) gene** located on chromosome 11q22.3. ### **Explanation of Options:** * **Correct Answer (B):** A-T is inherited in an **autosomal recessive** pattern. The ATM gene encodes a protein kinase responsible for repairing double-stranded DNA breaks. A deficiency leads to genomic instability, making cells hypersensitive to ionizing radiation. * **Option A (Incorrect):** It is not X-linked. Common X-linked immunodeficiencies include Wiskott-Aldrich Syndrome and Bruton’s Agammaglobulinemia. * **Option C (Incorrect):** A-T is characterized by **humoral and cellular immunodeficiency**. Typically, there are **decreased** levels of IgA, IgE, and IgG subclasses, rather than increased IgM. (Increased IgM is a hallmark of Hyper-IgM Syndrome). ### **High-Yield Clinical Pearls for NEET-PG:** 1. **The Triad:** Progressive cerebellar ataxia (early childhood), oculocutaneous telangiectasia (appearing at 3–6 years), and recurrent sinopulmonary infections. 2. **Diagnostic Marker:** Elevated **Serum Alpha-Fetoprotein (AFP)** levels are found in >95% of patients after age 2 (highly characteristic). 3. **Malignancy Risk:** Patients have a significantly increased risk of developing lymphomas and leukemias due to DNA repair defects. 4. **Radiosensitivity:** Patients are extremely sensitive to X-rays and radiotherapy; these should be avoided to prevent severe tissue damage. 5. **Neuropathology:** Purkinje cell degeneration in the cerebellum is the primary finding.

Q: DiGeorge syndrome is associated with all of the following except?

Hypocalcemia. **Explanation:** DiGeorge Syndrome (DGS) is a primary immunodeficiency caused by the **maldevelopment of the 3rd and 4th pharyngeal pouches**. This results in a classic triad of thymic hypoplasia (T-cell deficiency), parathyroid hypoplasia, and conotruncal cardiac defects. **Why Option A is the correct answer (The "Except"):** DiGeorge syndrome is associated with **Hypocalcemia**, not Hyperthyroidism. The failure of the 3rd and 4th pharyngeal pouches leads to **hypoplasia of the parathyroid glands**, resulting in low Parathyroid Hormone (PTH) levels and subsequent hypocalcemic tetany or seizures, typically presenting in the neonatal period. **Analysis of Incorrect Options:** * **Option B (Small jaws):** Micrognathia (small jaw) is a classic dysmorphic facial feature of DGS, along with low-set ears, hypertelorism, and a short philtrum. * **Option C (22q11 deletion):** This is the underlying genetic cause in >90% of cases. It is often detected via FISH (Fluorescence In Situ Hybridization). * **Option D (Hypocalcemia):** As explained above, this is a hallmark clinical finding due to parathyroid aplasia/hypoplasia. **High-Yield Clinical Pearls for NEET-PG:** * **CATCH-22 Mnemonic:** **C**ardiac defects (Truncus arteriosus/TOF), **A**bnormal facies, **T**hymic hypoplasia, **C**left palate, **H**ypocalcemia, **22**q11 deletion. * **Chest X-ray:** Characteristically shows an **absent thymic shadow**. * **Immunology:** Low T-cell count but normal B-cell count (though antibody production may be impaired). * **Velocardiofacial Syndrome:** A related spectrum disorder also involving 22q11 deletion but with more prominent cleft palate and facial dysmorphism.

Q: A 7-year-old boy presents with abdominal pain, joint aches, and a rash on his legs and feet. He has no history of frequent nosebleeds, easy bruising, or other episodes of abnormal bleeding. What is the most likely diagnosis?

Henoch-Schonlein purpura. **Explanation:** The clinical triad of **abdominal pain, arthralgia (joint aches), and a palpable purpuric rash** on the lower extremities in a child is the classic presentation of **Henoch-Schönlein Purpura (HSP)**, now also known as **IgA Vasculitis**. **Why Option D is correct:** HSP is a small-vessel vasculitis characterized by the deposition of **IgA-dominant immune complexes**. It typically follows an upper respiratory tract infection. The rash is characteristically "palpable purpura" (non-blanchable) found on gravity-dependent areas like the legs and buttocks. The absence of bleeding tendencies (normal platelet count) distinguishes it from thrombocytopenic purpuras. **Why other options are incorrect:** * **A. Acute Urticaria:** Presents as transient, itchy wheals (hives) that blanch on pressure. It does not cause purpura or systemic symptoms like joint pain and abdominal distress. * **B. DIC:** A life-threatening consumptive coagulopathy. While it causes purpura (purpura fulminans), patients are critically ill with active bleeding from multiple sites and abnormal coagulation profiles. * **C. Erythema Nodosum:** Presents as painful, erythematous, tender nodules, typically on the shins. It is a form of panniculitis (septal), not a vasculitic purpuric rash. **High-Yield Clinical Pearls for NEET-PG:** * **Most common systemic vasculitis in children.** * **Renal involvement:** IgA nephropathy (Berger’s disease-like) is the most serious long-term complication; monitor with serial urinalysis. * **Gastrointestinal:** Can lead to **intussusception** (usually ileo-ileal). * **Biopsy:** Shows **Leukocytoclastic vasculitis (LCV)** with IgA deposits on immunofluorescence. * **Platelet count:** Always **normal** (Non-thrombocytopenic purpura).

Question 1

Henoch-Schönlein purpura is characterized by all of the following except?

Accepted Answer

Thrombocytopenia

Answer

Glomerulonephritis

Answer

Arthralgia

Answer

Abdominal pain

Question 2

Which one of the following is not a feature of DiGeorge syndrome?

Accepted Answer

Rocker bottom feet

Answer

Congenital heart defects

Answer

Abnormalities of palate

Answer

Hypocalcemia

Question 3

A 1-year-old boy presents with a history of recurrent pneumonia, eczema, and prolonged bleeding after circumcision. A peripheral smear shows thrombocytopenia with small platelets. Which of the following is most likely to be deficient?

Accepted Answer

IgM

Answer

IgA

Answer

IgE

Answer

IgG

Question 4

A 5-month-old boy presented with spontaneous nosebleeds and bloody diarrhea. He also has a history of recurrent chest and ear infections requiring frequent hospitalizations. On examination, the child had atopic dermatitis and petechiae all over the body. Laboratory findings suggested an abnormally low platelet count along with eosinophilia. Which of the following statements is NOT true about this condition?

Accepted Answer

Low IgM and IgG levels.

Answer

There is progressive loss of T lymphocytes in the peripheral blood and in the T-cell zones (paracortical areas) of the lymph nodes.

Answer

High levels of IgA.

Answer

Patients are prone to developing B-cell lymphomas.

Question 5

An 8-month-old boy with a history of recurrent pneumonia is found to have almost no circulating IgG. Cellular immunity is normal. His brother had this same disease and died of echovirus encephalitis. His parents and sisters have normal serum levels of IgG. What is the appropriate diagnosis?

Accepted Answer

X-linked agammaglobulinemia of Bruton

Answer

DiGeorge syndrome

Answer

Isolated IgA deficiency

Answer

Wiskott Aldrich syndrome

Question 6

A 4-year-old boy presents with epistaxis. He has a history of recurrent respiratory tract infections and eczema. His uncle had similar problems. Physical examination reveals multiple petechial lesions on the skin and mucous membranes. Laboratory findings include increased serum IgE and decreased platelet count. Which of the following is the most likely diagnosis?

Accepted Answer

Wiskott-Aldrich syndrome

Answer

Acquired hypogammaglobulinemia

Answer

DiGeorge syndrome

Answer

Selective IgA deficiency

Question 7

Eye involvement is seen in which of the following subtypes of Juvenile Rheumatoid Arthritis?

Accepted Answer

Seronegative pauciarticular JRA, early onset

Answer

Seropositive pauciarticular JRA, late onset

Answer

Seronegative pauciarticular JRA, late onset

Answer

Seronegative polyarticular JRA, early onset

Question 8

Which of the following is true regarding ataxia telangiectasia?

Accepted Answer

It is an autosomal recessive disorder.

Answer

It is an X-linked recessive disease.

Answer

It is associated with increased levels of IgM.

Answer

None of the above.

Question 9

DiGeorge syndrome is associated with all of the following except?

Accepted Answer

Hypocalcemia

Answer

Hyperthyroidism

Answer

Small jaws

Answer

22q11 deletion

Question 10

A 7-year-old boy presents with abdominal pain, joint aches, and a rash on his legs and feet. He has no history of frequent nosebleeds, easy bruising, or other episodes of abnormal bleeding. What is the most likely diagnosis?

Accepted Answer

Henoch-Schonlein purpura

Answer

Acute urticaria

Answer

Disseminated intravascular coagulation (DIC)

Answer

Erythema nodosum

Immunology and Allergies — MCQs

Immunology and Allergies — MCQs

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