Immunology and Allergies Practice Questions

Q: Which antibody is seen in neonatal lupus with congenital heart block?

Anti-Ro (SS-A). **Explanation:** Neonatal Lupus Erythematosus (NLE) is a rare acquired autoimmune disorder caused by the transplacental passage of maternal IgG autoantibodies. **Why Anti-Ro (SS-A) is correct:** The pathogenesis of neonatal lupus, specifically **congenital heart block (CHB)**, is strongly associated with **Anti-Ro (SS-A)** and **Anti-La (SS-B)** antibodies. These antibodies cross the placenta and bind to fetal cardiac tissue, leading to inflammation (myocarditis) and subsequent fibrosis of the AV node. This damage is permanent and results in a third-degree heart block, which is the most serious complication of NLE. **Analysis of Incorrect Options:** * **A. Anti-ribosomal:** These antibodies are highly specific for Systemic Lupus Erythematosus (SLE) but are primarily associated with **neuropsychiatric manifestations** (lupus psychosis) in adults, not neonatal heart block. * **C. Anti-neuronal:** These are associated with paraneoplastic syndromes or neuropsychiatric SLE, but they do not play a role in the cardiac conduction defects of a neonate. * **D. Anti-histone:** This is the hallmark antibody for **Drug-Induced Lupus**. While it is a type of ANA, it is not implicated in the transplacental injury seen in NLE. **High-Yield Clinical Pearls for NEET-PG:** * **Most common manifestation of NLE:** Cutaneous lesions (erythematous, annular "raccoon-eye" rash), which are transient and disappear as maternal antibodies wane (approx. 6 months). * **Most serious manifestation:** Congenital Heart Block (permanent; often requires a pacemaker). * **Maternal status:** Many mothers are asymptomatic at the time of delivery but may later develop SLE or Sjögren’s syndrome. * **Recurrence risk:** If a mother has one child with NLE, the risk for subsequent pregnancies increases to approximately 15-20%.

Q: Which chromosome is defective in De-George syndrome?

22. **Explanation:** **DiGeorge Syndrome** (also known as 22q11.2 deletion syndrome) is caused by a microdeletion on the **long arm (q) of chromosome 22**. This genetic defect results in the failure of the **3rd and 4th pharyngeal pouches** to develop properly during embryogenesis. This leads to thymic hypoplasia (causing T-cell deficiency) and parathyroid hypoplasia (causing hypocalcemia). **Analysis of Options:** * **Option D (22): Correct.** The specific locus is 22q11.2. It is the most common microdeletion syndrome in humans. * **Option A (7): Incorrect.** Deletions on chromosome 7 (specifically 7q11.23) are associated with **Williams Syndrome** (characterized by elfin facies, hypercalcemia, and supravalvular aortic stenosis). * **Option B (15): Incorrect.** Chromosome 15 defects are linked to **Prader-Willi Syndrome** (paternal deletion) or **Angelman Syndrome** (maternal deletion) at the 15q11-q13 locus. * **Option C (17): Incorrect.** Chromosome 17 mutations are associated with **Neurofibromatosis Type 1** (17q11.2) and Miller-Dieker syndrome. **High-Yield Clinical Pearls (CATCH-22):** To remember the clinical features of DiGeorge Syndrome, use the mnemonic **CATCH-22**: * **C:** **C**ardiac defects (especially Conotruncal anomalies like Tetralogy of Fallot, Truncus Arteriosus). * **A:** **A**bnormal facies (low-set ears, hypertelorism). * **T:** **T**hymic aplasia/hypoplasia (leads to recurrent viral/fungal infections due to T-cell deficiency). * **C:** **C**left palate. * **H:** **H**ypocalcemia (due to parathyroid hypoplasia, often presenting as neonatal tetany/seizures). * **22:** Chromosome **22**q11 deletion.

Q: An 'en coup de sabre' lesion is characteristic of which condition?

Juvenile scleroderma. **Explanation** **Correct Answer: D. Juvenile scleroderma** **Underlying Medical Concept:** 'En coup de sabre' (French for "strike of the sword") is a classic clinical subtype of **Linear Morphea**, which falls under the umbrella of **Juvenile Localized Scleroderma (JLS)**. It presents as a linear, depressed, atrophic band of skin and subcutaneous tissue, typically occurring on the forehead or scalp. It may extend into the muscle or bone, occasionally leading to facial hemiatrophy (Parry-Romberg syndrome) or neurological complications like seizures. **Analysis of Incorrect Options:** * **A. Neonatal Lupus:** Characteristically presents with a "raccoon-eye" or annular erythematous rash. It is associated with congenital heart block and maternal anti-Ro/SSA or anti-La/SSB antibodies. * **B. Systemic Juvenile Idiopathic Arthritis (sJIA):** Presents with a classic "salmon-pink," evanescent (fleeting) maculopapular rash that typically coincides with fever spikes. * **C. Juvenile Dermatomyositis:** Features pathognomonic skin findings such as **Gottron papules** (over knuckles) and a **Heliotrope rash** (violaceous discoloration of the eyelids), along with proximal muscle weakness. **High-Yield Clinical Pearls for NEET-PG:** * **Localized Scleroderma (Morphea)** does *not* typically progress to systemic sclerosis (involvement of internal organs). * **CREST Syndrome** (Calcinosis, Raynaud’s, Esophageal dysmotility, Sclerodactyly, Telangiectasia) is associated with **Anti-centromere antibodies**. * **Systemic Sclerosis (Diffuse)** is associated with **Anti-Scl-70 (anti-topoisomerase I) antibodies**. * The most common form of localized scleroderma in children is the **Linear** type.

Q: A 24-year-old male presents with abdominal pain, rashes, palpable purpura, and arthritis. What is the most probable diagnosis?

Henoch-Schönlein Purpura (HSP). ### Explanation **Correct Answer: A. Henoch-Schönlein Purpura (HSP)** **Clinical Reasoning:** Henoch-Schönlein Purpura (now commonly termed **IgA Vasculitis**) is a small-vessel leukocytoclastic vasculitis characterized by the deposition of **IgA-dominant immune complexes**. The classic clinical tetrad presented in this case is pathognomonic: 1. **Palpable Purpura:** Non-thrombocytopenic, typically found on gravity-dependent areas (lower limbs/buttocks). 2. **Arthritis/Arthralgia:** Usually migratory and affecting large joints (knees/ankles). 3. **Abdominal Pain:** Due to bowel wall edema or intussusception. 4. **Renal Involvement:** Ranging from hematuria to glomerulonephritis. **Why other options are incorrect:** * **Sweet Syndrome:** An acute febrile neutrophilic dermatosis characterized by painful, erythematous plaques/nodules and fever, usually associated with malignancy or infections, rather than the IgA-mediated systemic tetrad. * **Meningococcemia:** Presents with a rapidly progressing petechial/purpuric rash and high-grade fever. Patients appear acutely toxic/septic with signs of meningitis or DIC, which is absent here. * **Kawasaki Disease:** Primarily affects children <5 years. Key features include prolonged fever, conjunctivitis, strawberry tongue, and coronary artery aneurysms, not the purpura-arthritis-abdominal pain triad. **High-Yield Pearls for NEET-PG:** * **Most common** systemic vasculitis in childhood (though it can occur in adults). * **Trigger:** Often follows an Upper Respiratory Tract Infection (URTI). * **Biopsy:** Shows leukocytoclastic vasculitis with **IgA and C3 deposition** on immunofluorescence. * **Complication:** Intussusception in HSP is typically **ileo-ileal** (unlike the common idiopathic ileo-colic type). * **Prognosis:** Generally excellent; long-term morbidity is determined by the severity of **renal involvement**.

Q: What laboratory evaluation is most likely to be abnormal in a 10-year-old patient with discrete facial erythema?

Creatine kinase. The clinical presentation of **discrete facial erythema** in a 10-year-old child is highly suggestive of the **Heliotrope rash** (violaceous erythema of the eyelids) or a malar-like rash associated with **Juvenile Dermatomyositis (JDM)**. ### Why Creatine Kinase (CK) is the Correct Answer: Juvenile Dermatomyositis is an autoimmune inflammatory myopathy. The hallmark of the disease is proximal muscle weakness and characteristic skin rashes. When muscle fibers are damaged due to inflammation (myositis), intracellular enzymes leak into the bloodstream. **Creatine Kinase (CK)** is the most sensitive laboratory marker for muscle destruction. Other elevated enzymes include LDH, AST, ALT, and Aldolase. ### Explanation of Incorrect Options: * **A. CD4 count:** This is used to monitor HIV/AIDS or certain primary immunodeficiencies (like SCID). While JDM involves T-cell dysregulation, the absolute CD4 count is not a diagnostic or characteristic marker for this condition. * **C. Rheumatoid factor (RF):** RF is typically associated with Juvenile Idiopathic Arthritis (JIA), specifically the polyarticular subtype. It is not a primary marker for Dermatomyositis. * **D. Thyrotropin (TSH):** While hypothyroidism can cause muscle weakness and skin changes (myxedema), it does not present with the discrete, inflammatory facial erythema characteristic of JDM. ### High-Yield Clinical Pearls for NEET-PG: * **Pathognomonic Signs:** Look for **Gottron papules** (erythematous scaly plaques over MCP/PIP joints) and **Heliotrope rash** (periorbital edema with purplish discoloration). * **Diagnosis:** Definitive diagnosis often involves elevated muscle enzymes, EMG findings, and **Muscle Biopsy** (showing perivascular atrophy). * **Complication:** **Calcinosis cutis** (calcium deposits in skin/muscle) is more common in the juvenile form than the adult form of dermatomyositis. * **First-line Treatment:** High-dose Corticosteroids and Methotrexate.

Q: All of the following are features of Hyper-IgE syndrome, except?

X-linked recessive inheritance. **Explanation:** **Hyper-IgE Syndrome (HIES)**, also known as **Job Syndrome**, is a primary immunodeficiency characterized by a triad of elevated serum IgE (>2000 IU/mL), recurrent "cold" staphylococcal abscesses, and pneumonia with pneumatocele formation. 1. **Why Option A is correct:** Hyper-IgE syndrome is primarily inherited in an **Autosomal Dominant (AD)** fashion due to a mutation in the **STAT3 gene** (most common type). There is also an Autosomal Recessive (AR) form caused by mutations in *DOCK8* or *TYK2*. It is **not** X-linked recessive. 2. **Why Options B, C, and D are incorrect:** These are classic clinical features of the AD-STAT3 form: * **Recurrent infections (B):** Patients suffer from "cold" abscesses (lacking typical signs of inflammation like warmth or redness) and recurrent pneumonia, often leading to permanent lung damage (pneumatoceles). * **Hyperextensibility and Skeletal features (C):** Non-immunological features are hallmark signs, including joint hypermobility, scoliosis, and osteopenia leading to recurrent fractures. * **Facial dysmorphy (D):** Characteristic "coarse facies" include a broad nasal bridge, deep-set eyes, a prominent forehead (frontal bossing), and a protruding jaw. **High-Yield Clinical Pearls for NEET-PG:** * **The "F's" of Job Syndrome:** **F**acies (coarse), **F**ractures (pathological), **F**ailed eruption of primary teeth (retained deciduous teeth), **F**ungal infections (candidiasis), and **F**ull of IgE. * **Pathophysiology:** STAT3 mutation leads to a failure of Th17 cell differentiation, resulting in impaired neutrophil recruitment to sites of infection. * **Differentiating Feature:** Unlike other immunodeficiencies, HIES involves both the immune system and the connective tissue/skeletal system.

Question 1

Which antibody is seen in neonatal lupus with congenital heart block?

Accepted Answer

Anti-Ro (SS-A)

Answer

Anti-ribosomal

Answer

Anti-neuronal

Answer

Anti-histone

Question 2

Which chromosome is defective in De-George syndrome?

Accepted Answer

22

Answer

7

Answer

15

Answer

17

Question 3

An 'en coup de sabre' lesion is characteristic of which condition?

Accepted Answer

Juvenile scleroderma

Answer

Neonatal lupus

Answer

Systemic juvenile idiopathic arthritis

Answer

Juvenile dermatomyositis

Question 4

A 24-year-old male presents with abdominal pain, rashes, palpable purpura, and arthritis. What is the most probable diagnosis?

Accepted Answer

Henoch-Schönlein Purpura (HSP)

Answer

Sweet syndrome

Answer

Meningococcemia

Answer

Hemochromatosis/Kawasaki Disease

Question 5

What laboratory evaluation is most likely to be abnormal in a 10-year-old patient with discrete facial erythema?

Accepted Answer

Creatine kinase

Answer

CD4 count

Answer

Rheumatoid factor

Answer

Thyrotropin

Question 6

A diagnosis of X-linked Agammaglobulinemia should be suspected if which of the following is present?

Accepted Answer

Absent tonsils and no palpable lymph nodes on physical examination

Answer

Female sex

Answer

High isohemagglutinin titers

Answer

Low CD3 count

Question 7

All of the following are features of Hyper-IgE syndrome, except?

Accepted Answer

X-linked recessive inheritance

Answer

Recurrent infections of skin and lung

Answer

Hyperextensibility of joints

Answer

Facial dysmorphy

Question 8

All of the following are seen in 22q 11.2 deletion syndrome except?

Accepted Answer

Learning disabilities

Answer

B cell immunodeficiency

Answer

Increased incidence of psychiatric disorders like schizophrenia in adulthood

Answer

Facial abnormalities

Question 9

A 6-year-old child presented to the OPD with an eczematous rash. On evaluation, the child was found to have fever and a platelet count of 80,000. On enquiry, there were multiple hospitalizations for recurrent infections. What is the most likely diagnosis?

Accepted Answer

Wiskott-Aldrich syndrome

Answer

Bruton's agammaglobulinemia

Answer

Chediak-Higashi syndrome

Answer

Severe combined immunodeficiency

Question 10

An 8-year-old boy presents with recurrent infections since infancy, hepatosplenomegaly, lymphadenopathy, and eczema-like dermatitis. Peripheral blood smear examination during a staphylococcal infection reveals impaired or absent neutrophil bactericidal capacity. What is the most likely cause of this child's illness?

Accepted Answer

Defect in the enzyme NADPH oxidase

Answer

Defect in the enzyme adenosine deaminase (ADA)

Answer

Defect in the IL-2 receptor

Answer

Developmental defect at the pre-B stage

Immunology and Allergies — MCQs

Immunology and Allergies — MCQs

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