Immunology and Allergies Practice Questions

Q: Fever in systemic juvenile Idiopathic Arthritis (sJIA) is characteristically?

Quotidian fever. **Explanation:** **Systemic Juvenile Idiopathic Arthritis (sJIA)**, formerly known as Still’s disease, is characterized by a distinct febrile pattern known as **Quotidian fever**. 1. **Why Quotidian fever is correct:** In sJIA, the fever is typically high-grade (≥39°C) and occurs once or twice daily (quotidian), usually in the late afternoon or evening. Crucially, the temperature returns to baseline (37°C) or even subnormal levels between spikes. This "spiking" pattern is a hallmark diagnostic criterion. 2. **Why other options are incorrect:** * **Evanescent:** This term describes the **rash** associated with sJIA (salmon-pink, non-pruritic, and fleeting), not the fever itself. * **Malarial fever:** This typically follows a tertian (48-hour) or quartan (72-hour) periodicity, unlike the daily spikes of sJIA. * **Continuous fever:** In this pattern, the temperature remains elevated with minimal fluctuation (less than 1°C variation). In sJIA, the temperature must touch the baseline. **High-Yield Clinical Pearls for NEET-PG:** * **IL-1 and IL-6:** These are the primary pro-inflammatory cytokines driving the pathogenesis of sJIA. * **Koebner Phenomenon:** The characteristic rash can be elicited by mild skin trauma or stroking. * **Laboratory Findings:** Marked leukocytosis, thrombocytosis, and highly elevated ESR/CRP are common. * **Complication:** **Macrophage Activation Syndrome (MAS)** is a life-threatening complication of sJIA, characterized by a sudden drop in ESR and fibrinogen levels despite worsening clinical status.

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.

Q: True about Severe Combined Immunodeficiency (SCID) in children is:

It is due to adenosine deaminase deficiency. **Explanation:** Severe Combined Immunodeficiency (SCID) is a pediatric emergency characterized by a profound defect in both **T-cell and B-cell** function. **1. Why Option A is Correct:** Adenosine Deaminase (ADA) deficiency is the **second most common cause** of SCID (autosomal recessive). ADA is an enzyme required to break down toxic metabolites (deoxyadenosine) within lymphocytes. Without it, these toxins accumulate, leading to the death of T, B, and NK cells. The most common cause overall is the **X-linked SCID** (IL-2 receptor gamma chain mutation). **2. Why Other Options are Incorrect:** * **Option B:** In SCID, **both** cellular (T-cell) and humoral (B-cell) immunity are severely affected. While B-cells may be present in some forms, they are non-functional due to the lack of T-cell help. * **Option C:** Live vaccines (e.g., BCG, OPV, MMR) are **strictly contraindicated** in SCID patients as they can cause fatal systemic infections. Even non-live vaccines are generally ineffective due to the inability to mount an immune response. * **Option D:** A hallmark of SCID is **thymic hypoplasia or dysplasia**. On a chest X-ray, the absence of a thymic shadow is a classic diagnostic clue. **Clinical Pearls for NEET-PG:** * **Presentation:** Recurrent severe infections (pneumonia, diarrhea, thrush), failure to thrive, and persistent lymphopenia (<1500 cells/mm³). * **Diagnosis:** Low absolute lymphocyte count and flow cytometry showing absent T-cells. * **Treatment:** Hematopoietic Stem Cell Transplant (HSCT) is the definitive treatment. ADA deficiency can also be treated with Enzyme Replacement Therapy (ERT) or Gene Therapy. * **Screening:** TRECs (T-cell Receptor Excision Circles) are used in newborn screening to detect SCID early.

Q: All of the following regarding Henoch-Schonlein Purpura (HSP) are true EXCEPT:

Steroids are the best treatment for skin lesions.. **Explanation:** Henoch-Schönlein Purpura (HSP), now termed **IgA Vasculitis**, is the most common systemic vasculitis in children. It is characterized by a tetrad of non-thrombocytopenic palpable purpura, arthritis/arthralgia, abdominal pain, and renal involvement. **Why Option B is the Correct Answer (The False Statement):** Steroids are **not** indicated for the treatment of skin lesions (purpura) in HSP. The rash is typically self-limiting and does not respond to corticosteroids. Steroids are primarily reserved for severe gastrointestinal involvement (to reduce pain and the risk of intussusception) or significant renal involvement. They do not prevent the onset of renal disease or shorten the duration of the rash. **Analysis of Other Options:** * **Option A (Hematuria):** Microscopic hematuria is common and usually resolves spontaneously without specific treatment. Only a small percentage of patients progress to chronic kidney disease. * **Option C (Arthralgia):** The arthritis in HSP is typically transient, non-deforming, and involves large joints (knees/ankles). It is self-limiting and responds well to NSAIDs. * **Option D (Prognosis):** The overall prognosis is excellent, with most children recovering fully within 4–6 weeks. The long-term prognosis depends almost entirely on the severity of renal involvement. **High-Yield Clinical Pearls for NEET-PG:** * **Pathogenesis:** IgA1-dominant immune complex deposition in small vessels. * **Classic Presentation:** Palpable purpura on dependent areas (buttocks and lower extremities) without thrombocytopenia (Normal Platelet Count). * **Renal Biopsy:** If performed, shows mesangial IgA deposition (identical to IgA Nephropathy/Berger’s Disease). * **Intussusception:** In HSP, it is often **ileo-ileal** (unlike the common ileo-colic type).

Q: A 4-year-old male presents with a recent onset of rash, urticaria, and fever of 101°F. The mother reports the child has been complaining of bone pain. Physical examination reveals mild lymphadenopathy. The patient recently completed a 10-day course of cefaclor suspension for an upper respiratory infection. How should this patient be treated?

Oral prednisone and diphenhydramine. ### **Explanation** The clinical presentation of fever, urticaria, lymphadenopathy, and arthralgia (bone pain) following the administration of a medication (cefaclor) is classic for **Serum Sickness-Like Reaction (SSLR)**. **Why Option D is Correct:** SSLR is a Type III hypersensitivity reaction caused by the deposition of immune complexes in small vessels. Unlike true Serum Sickness, it does not involve circulating immune complexes or low complement levels. The mainstay of treatment is **symptomatic relief** and removal of the offending agent. * **Antihistamines (Diphenhydramine):** Used to manage pruritus and urticaria. * **Corticosteroids (Oral Prednisone):** Indicated in moderate to severe cases, especially when there is significant joint pain (arthralgia) or high fever, to rapidly reduce inflammation. **Why Other Options are Incorrect:** * **Option A:** **Aspirin** is contraindicated in children with viral-like symptoms or febrile illnesses due to the risk of **Reye Syndrome**. * **Option B:** **Erythromycin** is an antibiotic. SSLR is an immunological reaction, not an active infection; adding another antibiotic may complicate the clinical picture. * **Option C:** **Penicillin** is a common trigger for SSLR. Administering it would worsen the hypersensitivity reaction. **High-Yield Clinical Pearls for NEET-PG:** * **Common Triggers:** Cefaclor (most common in children), Penicillins, and Sulfa drugs. * **Timing:** Symptoms typically appear **7–21 days** after drug exposure. * **Key Differentiator:** Unlike true Serum Sickness, SSLR lacks renal involvement (no proteinuria/hematuria) and complement levels (C3, C4) remain **normal**. * **Prognosis:** Excellent; symptoms usually resolve within 1–2 weeks of drug discontinuation.

Question 1

Fever in systemic juvenile Idiopathic Arthritis (sJIA) is characteristically?

Accepted Answer

Quotidian fever

Answer

Evanescent fever

Answer

Malarial fever

Answer

Continuous fever

Question 2

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 3

A 4-year-old boy presents with sudden onset of fever, abdominal pain and tenderness, hematuria, and palpable purpuric skin lesions on his buttocks and the extensor surfaces of his arms and legs. What is the most likely diagnosis?

Accepted Answer

Henoch-Schonlein purpura (HSP)

Answer

Idiopathic (immune) thrombocytopenic purpura (ITP)

Answer

Kawasaki disease

Answer

Polyarteritis nodosa

Question 4

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 5

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 6

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 7

True about Severe Combined Immunodeficiency (SCID) in children is:

Accepted Answer

It is due to adenosine deaminase deficiency

Answer

Humoral immunity is predominantly affected

Answer

Child should receive double dose of all vaccines

Answer

Patients with SCID have normal thymus

Question 8

All of the following regarding Henoch-Schonlein Purpura (HSP) are true EXCEPT:

Accepted Answer

Steroids are the best treatment for skin lesions.

Answer

Hematuria resolves without treatment.

Answer

Arthralgia is self-limiting.

Answer

The prognosis is generally excellent.

Question 9

A 4-year-old male presents with a recent onset of rash, urticaria, and fever of 101°F. The mother reports the child has been complaining of bone pain. Physical examination reveals mild lymphadenopathy. The patient recently completed a 10-day course of cefaclor suspension for an upper respiratory infection. How should this patient be treated?

Accepted Answer

Oral prednisone and diphenhydramine

Answer

Aspirin and diphenhydramine

Answer

Erythromycin and diphenhydramine

Answer

Intravenous penicillin and diphenhydramine

Question 10

A 9-year-old girl presents with a 6-month history of difficulty combing her hair and climbing upstairs. She exhibits a positive Gower's sign and a maculopapular rash over her metacarpophalangeal joints. What is the most appropriate next investigation?

Accepted Answer

Creatine Kinase (CK)

Answer

Erythrocyte Sedimentation Rate (ESR)

Answer

Rheumatoid Factor (RA factor)

Answer

Electromyography (EMG)

Immunology and Allergies — MCQs

Immunology and Allergies — MCQs

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