Immunology and Allergies Practice Questions

Q: What is the most common chronic arthritis seen in children?

Juvenile Rheumatoid Arthritis. **Explanation:** **Juvenile Rheumatoid Arthritis (JRA)**, now more commonly referred to as **Juvenile Idiopathic Arthritis (JIA)**, is the most common chronic arthritic condition in the pediatric population. It is defined as arthritis of unknown etiology persisting for at least 6 weeks in a child younger than 16 years. The pathogenesis involves a chronic T-cell mediated inflammatory response leading to synovial hypertrophy (pannus formation) and potential joint destruction. **Analysis of Options:** * **Rheumatic Arthritis (Rheumatoid Arthritis):** While common in adults, classic adult-onset RA is rare in children. JIA is a distinct clinical entity with different genetic markers (e.g., HLA-B27, HLA-DR4) and clinical subtypes (Oligoarticular, Polyarticular, Systemic). * **Rheumatic Fever:** This is an acute, non-suppurative inflammatory response following a Group A Streptococcal infection. While it causes "migratory polyarthritis," the joint involvement is typically **acute and transient**, not chronic, and usually leaves no permanent joint damage. * **Septic Arthritis:** This is an **acute bacterial infection** of the joint space (most commonly *S. aureus*). It is a medical emergency characterized by sudden onset, high fever, and monoarthritis. It is not a chronic condition. **Clinical Pearls for NEET-PG:** * **Oligoarticular JIA:** The most common subtype (approx. 50%). It carries the highest risk of **chronic asymptomatic uveitis**; regular slit-lamp exams are mandatory. * **Systemic JIA (Still’s Disease):** Characterized by daily "quotidian" fevers, evanescent salmon-pink rashes, and hepatosplenomegaly. * **Uveitis Marker:** Positive **ANA (Antinuclear Antibody)** in JIA is a strong predictor for the development of anterior uveitis. * **First-line Treatment:** NSAIDs are typically the initial therapy, followed by Methotrexate (DMARD) for persistent disease.

Q: A 10-year-old boy presents with a two-week history of fever, arthritis, and hepatosplenomegaly. What is the likely diagnosis?

Systemic onset Juvenile Idiopathic Arthritis. ### Explanation **Systemic onset Juvenile Idiopathic Arthritis (soJIA)**, formerly known as Still’s disease, is the most likely diagnosis. The classic triad of **prolonged fever, arthritis, and hepatosplenomegaly** (part of the reticuloendothelial involvement) is hallmark for this condition. The fever in soJIA is typically "quotidian" (spiking once or twice daily to >39°C and returning to baseline). Other common features include an evanescent, salmon-pink macular rash and lymphadenopathy. **Why other options are incorrect:** * **Acute Leukemia:** While it can present with fever, bone pain, and organomegaly, the "arthritis" in leukemia is usually severe bone pain rather than true joint swelling. A peripheral smear showing blasts would be diagnostic. * **Enteric Fever:** Presents with step-ladder fever and hepatosplenomegaly, but **arthritis is rare**. It typically features gastrointestinal symptoms and a relative bradycardia (Faget’s sign). * **Measles:** This is an acute viral illness characterized by the 3 C’s (Cough, Coryza, Conjunctivitis), Koplik spots, and a maculopapular rash. It does not cause chronic arthritis or significant hepatosplenomegaly over two weeks. **High-Yield Clinical Pearls for NEET-PG:** * **Diagnostic Criteria:** Fever for at least 2 weeks (with daily spikes for 3 days) plus arthritis in one or more joints. * **Laboratory Findings:** Marked leukocytosis (neutrophilia), thrombocytosis, and highly elevated ESR/CRP. * **Complication:** **Macrophage Activation Syndrome (MAS)** is a life-threatening complication of soJIA, characterized by a sudden drop in ESR and platelets with a paradoxical rise in Ferritin. * **Treatment:** NSAIDs are first-line; Biologics (IL-1 and IL-6 inhibitors like Anakinra or Tocilizumab) are used for refractory cases.

Q: What is the most common symptom of Henoch-Schönlein purpura?

Purpura. **Explanation:** Henoch-Schönlein Purpura (HSP), now commonly referred to as **IgA Vasculitis**, is the most common systemic vasculitis in children [1]. It is a small-vessel vasculitis characterized by the deposition of IgA-dominant immune complexes [1]. **1. Why Purpura is the correct answer:** **Purpura** is the hallmark of the disease and is present in **100% of cases** [1]. It typically presents as "palpable purpura" (raised, non-blanching lesions) distributed symmetrically over gravity-dependent areas, such as the lower extremities and buttocks [1]. While other symptoms are common, purpura is the defining clinical feature required for diagnosis. **2. Why the other options are incorrect:** * **Intussusception (A):** This is the most common *serious gastrointestinal complication* of HSP (specifically ileo-ileal), but it occurs in only about 1–5% of patients. * **Edema (C):** Subcutaneous edema (angioedema) is common in younger children (scalp, hands, feet), but it is less frequent than the skin rash itself. * **Vomiting (D):** This is a non-specific gastrointestinal symptom. While GI involvement (colicky pain) occurs in ~75% of cases, vomiting is a secondary feature and not the primary diagnostic sign. **High-Yield Clinical Pearls for NEET-PG:** * **Classic Triad:** Palpable purpura, arthritis/arthralgia, and abdominal pain [1]. * **Renal Involvement:** The most important prognostic factor is the severity of renal involvement (HSP nephritis), which histologically resembles **IgA Nephropathy (Berger’s disease)**. * **Trigger:** Often follows an **Upper Respiratory Tract Infection (URTI)**, frequently involving *Streptococcus* [1]. * **Platelet Count:** Characteristically **normal** (Non-thrombocytopenic purpura), which helps differentiate it from ITP.

Q: What is true about Henoch-Schonlein purpura?

IgA deposition in mesangium. **Henoch-Schönlein Purpura (HSP)**, now commonly referred to as **IgA Vasculitis**, is the most common systemic vasculitis in children. It is characterized by the deposition of immune complexes containing **Immunoglobulin A (IgA)** in the walls of small vessels [1]. ### **Explanation of Options** * **Correct Answer (C):** The hallmark of HSP is the deposition of **IgA-dominant immune complexes** in the mesangium of the kidneys (similar to IgA Nephropathy/Berger’s disease) and in the walls of small blood vessels in the skin and GI tract [1], [2]. This triggers an inflammatory response leading to the clinical manifestations. * **Option A:** HSP is a **small-vessel vasculitis**, not a medium-vessel vasculitis (like Polyarteritis Nodosa or Kawasaki disease) [1]. It primarily affects arterioles, capillaries, and venules. * **Option B:** While skin rashes are often the presenting sign, renal involvement (HSP nephritis) typically occurs **early**, usually within 4–6 weeks of the initial presentation [2]. Monitoring for hematuria and proteinuria is critical during the acute phase. * **Option D:** HSP is a **non-thrombocytopenic purpura**. The platelet count is characteristically **normal or high** (inflammatory marker). The purpura is "palpable" because it is caused by vessel wall inflammation (vasculitis), not a deficiency in platelets. ### **High-Yield Clinical Pearls for NEET-PG** * **Classic Tetrad:** 1. Palpable purpura (without thrombocytopenia), 2. Arthralgia/Arthritis, 3. Abdominal pain (may lead to intussusception), 4. Renal disease. * **Trigger:** Often follows an **Upper Respiratory Tract Infection (URTI)** [1], [2]. * **Diagnosis:** Primarily clinical; skin biopsy shows **leukocytoclastic vasculitis** with IgA deposits on immunofluorescence. * **Prognosis:** Generally excellent and self-limiting; the long-term prognosis depends entirely on the severity of **renal involvement** [2].

Q: A full-term baby boy is delivered after an uneventful pregnancy and is well for the first 2 years of his life. He receives all his immunizations without any complications. Starting around his second birthday, the mother begins to note frequent upper respiratory tract infections, and the child is hospitalized three times for pneumonia. Laboratory testing would most likely reveal a deficiency of which of the following immunoglobulins in this child?

IgA. **Explanation:** The clinical presentation is characteristic of **Selective IgA Deficiency**, the most common primary immunodeficiency. **Why IgA is the correct answer:** IgA is the primary immunoglobulin found in mucosal secretions (respiratory, GI, and urogenital tracts). It acts as the first line of defense against pathogens. A deficiency leads to recurrent sinopulmonary infections (sinusitis, pneumonia) and gastrointestinal infections (e.g., *Giardia*). The child remained healthy for the first two years because IgA deficiency often presents later in childhood, and many patients remain asymptomatic. Crucially, the patient tolerated **vaccinations** (which are mostly systemic/IM) without complications, indicating that his humoral (IgG/IgM) and cellular immunity are intact. **Why other options are incorrect:** * **IgG Deficiency (C):** IgG is the most abundant serum antibody. A deficiency (like X-linked Agammaglobulinemia) usually presents after 6 months of age (once maternal IgG wanes) with severe, systemic pyogenic infections. These patients also react poorly to live vaccines. * **IgM Deficiency (D):** Isolated IgM deficiency is rare. IgM is the first antibody produced in response to an antigen; its absence would lead to severe disseminated infections early in life. * **IgD (B):** IgD functions primarily as an antigen receptor on B-cell surfaces; its isolated deficiency is not a recognized cause of recurrent respiratory infections. **NEET-PG High-Yield Pearls:** * **Most Common:** Selective IgA Deficiency is the most common primary immunodeficiency. * **Associated Conditions:** High association with **Celiac disease**, autoimmune disorders, and atopy. * **The "Anaphylaxis" Rule:** Patients with IgA deficiency are at high risk of **anaphylaxis during blood transfusions** because they develop anti-IgA antibodies. * **Diagnosis:** Serum IgA levels < 7 mg/dL with normal IgG and IgM levels.

Q: Which of the following vasculitides is typically not seen in adults?

Kawasaki disease. **Explanation:** **Kawasaki Disease (KD)** is the correct answer because it is an acute, self-limiting systemic vasculitis that almost exclusively affects infants and young children (85% of cases occur under age 5). While rare adult-onset cases exist, it is classically defined as a pediatric condition. It is a medium-vessel vasculitis with a predilection for the coronary arteries. **Analysis of Options:** * **Takayasu Arteritis (A):** Known as "pulseless disease," this large-vessel vasculitis typically affects young women (usually between ages 15 and 40). It is a classic adult/adolescent diagnosis. * **Susac Syndrome (B):** A rare microangiopathy characterized by the clinical triad of encephalopathy, branch retinal artery occlusions, and sensorineural hearing loss. It primarily affects young adults (ages 20–40). * **Henoch-Schönlein Purpura (C):** While HSP is the most common vasculitis in children, it is frequently seen in adults as well. In adults, the disease often presents with a more severe clinical course and a higher risk of significant renal involvement compared to children. **High-Yield Clinical Pearls for NEET-PG:** * **Kawasaki Diagnostic Criteria (CRASH and Burn):** **C**onjunctivitis (bilateral, non-exudative), **R**ash (polymorphous), **A**denopathy (cervical, usually unilateral), **S**trawberry tongue (and oral mucosal changes), **H**ands/feet (edema/desquamation), and **Burn** (High-grade fever for ≥5 days). * **Complication:** Coronary artery aneurysms are the most feared complication; **Echocardiography** is the mandatory initial investigation. * **Treatment:** High-dose IVIG + Aspirin (Note: This is one of the few pediatric indications where Aspirin is used despite the risk of Reye’s syndrome).

Q: Juvenile idiopathic arthritis includes all except:

Reactive arthritis. **Explanation:** Juvenile Idiopathic Arthritis (JIA) is a heterogeneous group of chronic inflammatory arthritides occurring in children under the age of 16, with symptoms persisting for at least 6 weeks. The classification is based on the **ILAR (International League of Associations for Rheumatology) criteria**, which defines specific subtypes. **Why Reactive Arthritis is the correct answer:** Reactive arthritis is a form of spondyloarthropathy that occurs following a gastrointestinal or genitourinary infection (e.g., *Salmonella*, *Shigella*, or *Chlamydia*). While it can occur in children, it is categorized as a separate clinical entity and is **not** included under the ILAR classification of JIA. **Why the other options are incorrect:** The ILAR classification specifically includes the following as subtypes of JIA: * **Systemic JIA:** Characterized by arthritis and daily "quotidian" fevers, often accompanied by an evanescent salmon-pink rash and organomegaly. * **Psoriatic JIA:** Arthritis associated with psoriasis or specific minor criteria (dactylitis, nail pitting). * **Enthesitis-related JIA:** Typically affects males >6 years old; involves inflammation at the site where tendons/ligaments attach to bone (entheses), often HLA-B27 positive. * **Other subtypes:** Oligoarticular (most common), Polyarticular (RF positive or negative), and Undifferentiated arthritis. **High-Yield Clinical Pearls for NEET-PG:** * **Most common subtype:** Oligoarticular JIA (affects ≤4 joints). * **Most common complication:** Chronic anterior uveitis (especially in ANA-positive patients); requires frequent slit-lamp exams. * **Macrophage Activation Syndrome (MAS):** A life-threatening complication most commonly associated with **Systemic JIA**. * **Uveitis Risk:** Highest in girls with early-onset oligoarthritis who are **ANA positive**.

Question 1

What is the most common chronic arthritis seen in children?

Accepted Answer

Juvenile Rheumatoid Arthritis

Answer

Rheumatic Arthritis

Answer

Rheumatic Fever

Answer

Septic Arthritis

Question 2

A 4-month-old boy presented with spontaneous nose bleeds and bloody diarrhea. He has a history of recurrent chest and ear infections, leading to frequent hospitalizations. Examination revealed atopic dermatitis and petechiae all over the body. Laboratory findings suggested abnormally low platelet counts along with eosinophilia. The gene involved in this condition is located on which chromosome?

Accepted Answer

X-chromosome

Answer

Chromosome 21

Answer

Chromosome 23

Answer

Chromosome 1

Question 3

A 10-year-old boy presents with a two-week history of fever, arthritis, and hepatosplenomegaly. What is the likely diagnosis?

Accepted Answer

Systemic onset Juvenile Idiopathic Arthritis

Answer

Acute Leukemia

Answer

Enteric fever

Answer

Measles

Question 4

What is the most common symptom of Henoch-Schönlein purpura?

Accepted Answer

Purpura

Answer

Intussusception

Answer

Edema

Answer

Vomiting

Question 5

What is true about Henoch-Schonlein purpura?

Accepted Answer

IgA deposition in mesangium

Answer

Medium vessel vasculitis

Answer

Renal symptoms start late in the disease

Answer

Low platelet count

Question 6

A full-term baby boy is delivered after an uneventful pregnancy and is well for the first 2 years of his life. He receives all his immunizations without any complications. Starting around his second birthday, the mother begins to note frequent upper respiratory tract infections, and the child is hospitalized three times for pneumonia. Laboratory testing would most likely reveal a deficiency of which of the following immunoglobulins in this child?

Accepted Answer

IgA

Answer

IgD

Answer

IgG

Answer

IgM

Question 7

Which of the following vasculitides is typically not seen in adults?

Accepted Answer

Kawasaki disease

Answer

Takayasu arteritis

Answer

Susac syndrome

Answer

Henoch-Schönlein purpura

Question 8

Juvenile idiopathic arthritis includes all except:

Accepted Answer

Reactive arthritis

Answer

Psoriatic arthritis

Answer

Enthesis-related arthritis

Answer

Systemic arthritis

Question 9

A 7-year-old boy presents with cramping abdominal pain and a rash primarily affecting the back of his legs and buttocks, as well as the extensor surfaces of his forearms. Laboratory analysis reveals proteinuria and micro-hematuria. In addition to his rash and abdominal pain, what other finding is he likely to have?

Accepted Answer

Arthritis or arthralgia

Answer

Chronic renal failure

Answer

Seizures

Answer

Unilateral lymphadenopathy

Question 10

In which of the following conditions are immunoglobulins indicated for a viral infection?

Accepted Answer

Severe Combined Immunodeficiency (SCID)

Answer

Human Immunodeficiency Virus (HIV)

Answer

Dengue fever

Answer

Severe malnutrition

Immunology and Allergies — MCQs

Immunology and Allergies — MCQs

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