Immunology and Allergies Practice Questions

Q: Uveitis is most commonly associated with which of the following conditions?

Pauciarticular juvenile idiopathic arthritis. **Explanation:** The association between Juvenile Idiopathic Arthritis (JIA) and uveitis is a high-yield topic in Pediatrics. Chronic non-granulomatous anterior uveitis (iridocyclitis) is most strongly associated with **Pauciarticular (Oligoarticular) JIA**. **1. Why Pauciarticular JIA is correct:** Pauciarticular JIA involves $\le$ 4 joints during the first 6 months of disease. It carries the highest risk for uveitis, especially in patients who are **ANA (Antinuclear Antibody) positive**. The uveitis is typically asymptomatic and "white," meaning it lacks the classic red-eye presentation, making regular slit-lamp examinations mandatory to prevent blindness. **2. Analysis of Incorrect Options:** * **Rheumatoid Arthritis (RA):** While RA in adults is associated with episcleritis and scleritis, it is rarely associated with anterior uveitis. * **Systemic JIA (Still’s Disease):** This subtype is characterized by high-grade fever, evanescent rash, and hepatosplenomegaly. Interestingly, uveitis is **extremely rare** in the systemic form. * **Polyarticular JIA:** This involves $\ge$ 5 joints. While uveitis can occur in this subtype, the incidence is significantly lower (approx. 5-10%) compared to the Pauciarticular subtype (approx. 20%). **Clinical Pearls for NEET-PG:** * **Risk Factors for Uveitis in JIA:** Pauciarticular onset, Female gender, and **ANA positivity** (the strongest predictor). * **Screening:** ANA-positive Pauciarticular JIA patients require slit-lamp exams every 3 months. * **Treatment:** First-line treatment for JIA-associated uveitis includes topical steroids and cycloplegics; Methotrexate is the preferred systemic DMARD for refractory cases. * **HLA Association:** Pauciarticular JIA is often associated with HLA-DR8, DR5, and DRw52.

Q: A child with agammaglobulinemia presents with respiratory tract infection and diarrhea. What is the most likely infectious agent?

Rotavirus. **Explanation:** In patients with **X-linked Agammaglobulinemia (Bruton’s)**, there is a profound deficiency of B-cells and all classes of immunoglobulins (IgG, IgA, IgM). The lack of **Secretory IgA** at mucosal surfaces makes these children highly susceptible to specific gastrointestinal and respiratory pathogens. 1. **Why Rotavirus is correct:** While these patients are classically associated with *Giardia lamblia* (due to lack of IgA), **Rotavirus** is the most common viral cause of severe diarrhea in children with agammaglobulinemia. In the absence of neutralizing antibodies, viral clearance is impaired, leading to prolonged and severe gastroenteritis. 2. **Why other options are incorrect:** * **Coxsackievirus:** While patients with agammaglobulinemia are uniquely susceptible to **Enteroviruses** (like Polio, Echovirus, and Coxsackie), these typically manifest as chronic progressive **meningoencephalitis** or dermatomyositis-like syndromes rather than isolated diarrhea. * **Shigella:** This is an invasive bacterial pathogen. While humoral immunity plays a role, the primary defect in agammaglobulinemia predisposes more significantly to encapsulated bacteria (like *S. pneumoniae* and *H. influenzae*) and specific protozoa/viruses rather than typical bacillary dysentery. **High-Yield Clinical Pearls for NEET-PG:** * **Classic Triad:** Absent B-cells (CD19/20+), absent tonsils/lymph nodes, and recurrent pyogenic infections after 6 months of age (once maternal IgG wanes). * **Most common GI parasite:** *Giardia lamblia*. * **Most common CNS complication:** Chronic Enteroviral Encephalitis. * **Contraindication:** Live vaccines (OPV, Rotavirus vaccine, MMR) are strictly contraindicated. * **Treatment:** Intravenous Immunoglobulin (IVIG) replacement.

Q: What is the age criterion for Juvenile Rheumatoid Arthritis (JRA)?

Less than 16 years. ### Explanation **Juvenile Idiopathic Arthritis (JIA)**, formerly known as Juvenile Rheumatoid Arthritis (JRA), is the most common chronic rheumatic disease of childhood. According to the International League of Associations for Rheumatology (ILAR) and the American College of Rheumatology (ACR), the diagnosis requires the onset of persistent arthritis in one or more joints for at least **6 weeks** in a child **less than 16 years of age**, after excluding other known conditions (e.g., trauma, infection, malignancy). **Why Option D is Correct:** The age cutoff of 16 years is the standard clinical definition used to differentiate pediatric inflammatory arthritides from adult-onset Rheumatoid Arthritis. This distinction is crucial because the clinical presentation, genetic associations (HLA types), and prognosis in children differ significantly from adults. **Why Other Options are Incorrect:** * **Options A, B, and C:** While JIA can certainly manifest at ages 10, 12, or 14, these are not the upper age limits for the diagnostic criteria. Setting the limit too low would misclassify adolescents (aged 14–15) who present with the same pediatric-specific pathophysiology. **High-Yield Clinical Pearls for NEET-PG:** * **Subtypes:** The most common subtype is **Oligoarticular JIA** (involving ≤4 joints), which carries a high risk of **asymptomatic chronic anterior uveitis**. * **Systemic JIA (Still’s Disease):** Characterized by daily "quotidian" fevers, evanescent salmon-pink rashes, and hepatosplenomegaly. It is often associated with **Macrophage Activation Syndrome (MAS)**. * **Markers:** Rheumatoid Factor (RF) is usually negative in children (only 5-10% are RF positive). **ANA positivity** is a strong predictor for the development of uveitis. * **First-line Treatment:** NSAIDs are the initial therapy; Methotrexate is the most common DMARD used for persistent disease.

Q: Which one of the following vaccines is contraindicated in children with egg allergy?

Yellow Fever. **Explanation:** The correct answer is **Yellow Fever**. The underlying medical concept relates to the manufacturing process of vaccines. Certain vaccines are cultured in **embryonated chicken eggs** or chick embryo cell cultures. During the purification process, trace amounts of egg proteins (specifically **ovalbumin**) may remain in the final product, potentially triggering an anaphylactic reaction in sensitized individuals. **Why Yellow Fever is the correct answer:** The Yellow Fever vaccine is grown directly in chicken embryos. It contains a higher concentration of egg protein compared to other vaccines, making it strictly contraindicated in individuals with a history of severe egg allergy (anaphylaxis). **Analysis of Incorrect Options:** * **MMR (Measles, Mumps, Rubella):** Although the Measles and Mumps components are grown in chick embryo fibroblast cultures, the amount of egg protein is negligible. Large-scale studies have proven that MMR is **safe** for children with egg allergies, and it can be administered in a routine primary care setting. * **DPT (Diphtheria, Pertussis, Tetanus):** This is a toxoid/subunit vaccine produced using synthetic media; it contains no egg protein. * **BCG (Bacillus Calmette–Guérin):** This is a live attenuated bacterial vaccine (derived from *Mycobacterium bovis*) and does not involve egg-based cultivation. **High-Yield Clinical Pearls for NEET-PG:** * **Egg-containing vaccines:** Yellow Fever and Influenza (most formulations) are the primary concerns. * **Influenza Vaccine:** Most children with egg allergy can now receive the inactivated influenza vaccine (IIV) in a standard medical setting, but Yellow Fever remains the most "high-risk" in exams. * **Rabies Vaccine:** The Chick Embryo Cell Vaccine (PCECV) should be used with caution in egg-allergic patients; Human Diploid Cell Vaccine (HDCV) is the preferred alternative.

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: An 8-month-old boy is evaluated because of repeated episodes of pneumococcal pneumonia. Serum studies demonstrate very low levels of IgM, IgG, and IgA. This patient's condition is related to a deficiency of which of the following proteins?

Tyrosine kinase. **Explanation:** The clinical presentation of an 8-month-old boy with recurrent pyogenic infections (specifically *Streptococcus pneumoniae*) and pan-hypogammaglobulinemia (low IgM, IgG, and IgA) is classic for **X-linked Agammaglobulinemia (XLA)**, also known as Bruton’s Agammaglobulinemia. **1. Why Tyrosine Kinase is Correct:** XLA is caused by a mutation in the **Bruton Tyrosine Kinase (BTK) gene**. This cytoplasmic tyrosine kinase is essential for B-cell signal transduction. Without functional BTK, B-cell precursors (Pre-B cells) in the bone marrow fail to mature into mature B-cells. Consequently, there is a complete absence of B-cells in the peripheral blood, leading to a lack of plasma cells and a failure to produce all classes of antibodies. **2. Why the Incorrect Options are Wrong:** * **Adenosine deaminase (ADA):** Deficiency leads to **SCID** (Autosomal Recessive). It causes the accumulation of toxic metabolites that destroy both B and T lymphocytes. * **Class III MHC gene:** These genes encode components of the complement system (C2, C4) and TNF. Deficiencies do not typically present with pan-hypogammaglobulinemia. * **Gamma chain of the IL-2 receptor:** This is the most common cause of **X-linked SCID**. It results in a lack of T-cells and NK cells, with secondary B-cell dysfunction. **Clinical Pearls for NEET-PG:** * **Age of Onset:** Symptoms typically appear after **6 months** of age, once maternal IgG wanes. * **Physical Exam:** Look for **absent or hypoplastic tonsils** and lymph nodes (due to lack of germinal centers). * **Infections:** Increased susceptibility to encapsulated bacteria (*H. influenzae, S. pneumoniae*) and certain viruses/parasites (Enteroviruses, *Giardia*). * **Diagnosis:** Flow cytometry showing **CD19+ B-cell count <2%**.

Question 1

A 3-year-old child presents with recurrent pneumonia, eczema, and thrombocytopenia. Which protein synthesis is abnormal in this child?

Accepted Answer

Wiskott-Aldrich syndrome protein (WASp)

Answer

Hamartin

Answer

Adenosine deaminase

Answer

HLA-A1

Question 2

Uveitis is most commonly associated with which of the following conditions?

Accepted Answer

Pauciarticular juvenile idiopathic arthritis

Answer

Rheumatoid arthritis

Answer

Systemic juvenile idiopathic arthritis

Answer

Polyarticular juvenile idiopathic arthritis

Question 3

What is the most common cause of liver abscess in chronic granulomatous disease?

Accepted Answer

Staphylococcus aureus

Answer

Klebsiella

Answer

Peptostreptococcus

Answer

E.coli

Question 4

A child with agammaglobulinemia presents with respiratory tract infection and diarrhea. What is the most likely infectious agent?

Accepted Answer

Rotavirus

Answer

Cocksackie virus

Answer

Shigella

Answer

None of the above

Question 5

What is the age criterion for Juvenile Rheumatoid Arthritis (JRA)?

Accepted Answer

Less than 16 years

Answer

Less than 10 years

Answer

Less than 12 years

Answer

Less than 14 years

Question 6

A two-year-old male child completed an 8-day course of cefaclor. He then developed low-grade fever, malaise, lymphadenopathy, irritability, and a generalized erythematous rash that is mildly pruritic. What is the most probable diagnosis?

Accepted Answer

Type 3 hypersensitivity

Answer

Kawasaki disease

Answer

Partially treated meningitis

Answer

IMN

Question 7

Which one of the following vaccines is contraindicated in children with egg allergy?

Accepted Answer

Yellow Fever

Answer

MMR

Answer

DPT

Answer

BCG

Question 8

A 9-year-old male child presented with a history of spiking fevers from the last 2 months, which have been as high as 104°F. On examination, he has spindle-shaped swelling of multiple finger joints and complains of upper sternal pain. When he had fever, his mother noticed a salmon-colored rash that resolves with the resolution of the fever. He had no conjunctivitis or any oral ulcers, but his heart sounds are muffled and he has pulsus paradoxus. Which of the following is the most likely diagnosis?

Accepted Answer

Juvenile idiopathic arthritis

Answer

Toxic synovitis

Answer

Rheumatic fever

Answer

Septic arthritis

Question 9

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 10

An 8-month-old boy is evaluated because of repeated episodes of pneumococcal pneumonia. Serum studies demonstrate very low levels of IgM, IgG, and IgA. This patient's condition is related to a deficiency of which of the following proteins?

Accepted Answer

Tyrosine kinase

Answer

Adenosine deaminase

Answer

Class III MHC gene

Answer

Gamma chain of the IL-2 receptor

Immunology and Allergies — MCQs

Immunology and Allergies — MCQs

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