Immunology and Allergies Practice Questions

Q: What is a characteristic feature of Systemic Juvenile Idiopathic Arthritis?

RA factor is negative. ### Explanation **Systemic Juvenile Idiopathic Arthritis (sJIA)**, also known as Still’s disease, is a unique subtype of JIA characterized by prominent extra-articular features. **Why the correct answer is right:** In sJIA, the **Rheumatoid Factor (RF) is characteristically negative**. Unlike the polyarticular subtype (which can be RF positive), sJIA is considered an autoinflammatory disease rather than a classic autoimmune disease. Diagnosis is clinical, based on the presence of arthritis in one or more joints associated with (or preceded by) a fever of at least 2 weeks' duration that is daily ("quotidian") for at least 3 days, accompanied by features like an evanescent salmon-pink rash, lymphadenopathy, or serositis. **Analysis of Incorrect Options:** * **A. Uveitis is a feature:** This is incorrect for sJIA. Chronic anterior uveitis is a classic complication of **Oligoarticular JIA** (especially if ANA positive). Uveitis is very rare in the systemic subtype. * **B. It occurs after 16 years of age:** By definition, JIA must have an onset **before the age of 16**. If similar symptoms occur after 16, it is termed Adult-Onset Still’s Disease (AOSD). * **C. NSAIDs are contraindicated:** This is false. NSAIDs are often the **first-line** symptomatic treatment for pain and fever in JIA, though systemic steroids or biologics (IL-1 and IL-6 inhibitors) are usually required for definitive control. **High-Yield Clinical Pearls for NEET-PG:** * **Fever Pattern:** Classic "Quotidian" fever (spikes once daily, usually in the evening, returning to baseline). * **Laboratory Markers:** Marked leukocytosis, thrombocytosis, and highly elevated ESR/CRP. * **Ferritin:** Extremely high ferritin levels are common and can signal the onset of **Macrophage Activation Syndrome (MAS)**, a life-threatening complication of sJIA. * **Biologics of Choice:** Tocilizumab (IL-6 inhibitor) and Anakinra/Canakinumab (IL-1 inhibitors).

Q: An 8-year-old child has had abdominal pain and dark urine for 10 days. Physical examination shows blotchy purple skin lesions on the trunk and extremities. Urinalysis shows hematuria and proteinuria. Serologic test results are negative for myeloperoxidase-antineutrophil cytoplasmic antibody (MPO-ANCA) and proteinase 3-antineutrophil cytoplasmic antibody (PR3-ANCA). A skin biopsy specimen shows necrotizing vasculitis of small dermal vessels. A renal biopsy specimen shows immune complex deposition in glomeruli, with some IgA-rich immune complexes. Which of the following is the most likely diagnosis?

Henoch-Schonlein purpura. **Explanation:** The clinical presentation of **abdominal pain, dark urine (hematuria), and palpable purpura** (blotchy purple lesions) in a child is the classic triad of **Henoch-Schönlein Purpura (HSP)**, now commonly referred to as **IgA Vasculitis**. **Why Option B is Correct:** HSP is a small-vessel vasculitis characterized by the deposition of **IgA-dominant immune complexes**. The skin biopsy showing necrotizing vasculitis of small dermal vessels (leukocytoclastic vasculitis) and the renal biopsy showing IgA-rich deposits in the mesangium are pathognomonic. The negative ANCA results help rule out ANCA-associated vasculitides like Granulomatosis with polyangiitis. **Why Other Options are Incorrect:** * **A & D (Giant cell & Takayasu arteritis):** These are **large-vessel vasculitides**. They typically present with absent pulses, bruits, or temporal headaches and do not feature IgA-mediated glomerulonephritis or small-vessel dermal vasculitis. * **C (Polyarteritis nodosa):** This is a **medium-vessel vasculitis**. While it can cause abdominal pain (mesenteric ischemia) and renal involvement, it typically spares the capillaries (glomeruli) and is not associated with IgA deposition. **High-Yield Clinical Pearls for NEET-PG:** * **Most common** systemic vasculitis in children. * **Classic Tetrad:** Palpable purpura (without thrombocytopenia), arthralgia, abdominal pain, and renal disease. * **Triggers:** Often follows an Upper Respiratory Tract Infection (URTI). * **Renal Pathology:** Identical to **IgA Nephropathy (Berger’s disease)**; however, HSP is a systemic multisystem involvement, whereas Berger’s is localized to the kidney. * **Treatment:** Usually supportive; steroids are used for severe gastrointestinal or renal involvement.

Q: A child presents with delayed separation of the umbilical cord, leukocytosis, Down syndrome, and recurrent infections. What is the most likely diagnosis?

Leukocyte Adhesion Deficiency. ### Explanation **Correct Option: A. Leukocyte Adhesion Deficiency (LAD)** **Why it is correct:** Leukocyte Adhesion Deficiency (Type 1) is a primary immunodeficiency caused by a defect in the **CD18 subunit of $\beta_2$-integrins**. This defect prevents neutrophils from adhering to the vascular endothelium and migrating into tissues (diapedesis). * **Delayed separation of the umbilical cord:** This is the classic hallmark of LAD. Normally, neutrophils infiltrate the cord stump to facilitate its detachment; in LAD, the absence of neutrophils at the site leads to delayed separation (often >30 days). * **Leukocytosis:** Because neutrophils cannot leave the bloodstream to enter tissues, they accumulate in the blood, leading to persistent, marked neutrophilic leukocytosis. * **Recurrent Infections:** Patients suffer from skin and mucosal infections (e.g., omphalitis, periodontitis) characterized by a **lack of pus formation** despite high white cell counts. * **Association:** While not a primary feature, LAD has been documented in case reports involving children with Down syndrome. **Why other options are incorrect:** * **B. Neonatal Sepsis:** While sepsis causes leukocytosis and infections, it does not explain the specific anatomical delay in umbilical cord separation. * **C. Histiocytosis-X (Langerhans Cell Histiocytosis):** This typically presents with seborrheic-like skin rashes, lytic bone lesions, and hepatosplenomegaly, rather than a specific defect in cord separation or integrin function. **High-Yield Clinical Pearls for NEET-PG:** * **LAD Type 1:** Defect in **CD18** (Integrins). * **LAD Type 2:** Defect in **Sialyl-Lewis X** (Selectins); presents with short stature and intellectual disability. * **Key Triad:** Delayed cord separation + Recurrent "cold" infections (no pus) + Extreme neutrophilia. * **Diagnosis:** Confirmed by **Flow Cytometry** showing decreased expression of CD11/CD18.

Q: A 5-year-old male child presents with a history of recurrent infections and rashes, as shown in the image. Routine blood investigations reveal thrombocytopenia. Which of the following diagnoses is most likely?

Wiskott Aldrich syndrome. ***Wiskott Aldrich syndrome*** - Classic **WAS triad** of **thrombocytopenia**, **eczematous rashes**, and **recurrent infections** (immunodeficiency) perfectly matches this presentation. - **X-linked inheritance** affecting males with characteristically **small platelet size** distinguishes it from other thrombocytopenic conditions. *Job syndrome* - Characterized by **recurrent skin and lung infections** with **eosinophilia** and elevated **IgE levels**. - **Normal platelet count** is typical, making thrombocytopenia inconsistent with this diagnosis. *Measles* - Acute viral illness with **Koplik spots**, **maculopapular rash**, and **fever** following a prodromal phase. - **Transient thrombocytopenia** may occur but recurrent infections and chronic eczematous rashes are not characteristic features. *Henoch Schonlein purpura* - **IgA-mediated vasculitis** presenting with **palpable purpura**, **arthritis**, and **glomerulonephritis**. - **Normal platelet count** is characteristic as purpura results from vasculitis, not thrombocytopenia.

Question 1

A 2.5-year-old boy is brought to the nutrition clinic. He was born at term with a birth weight of 3.0 kg. His mother reports that since weaning he has been fed almost exclusively on a maize-based porridge with minimal animal protein or legumes. On examination, he weighs 9.8 kg and has a height of 82 cm. He has bilateral pitting oedema up to the ankles, generalised skin changes with areas of hyperpigmentation and hypopigmentation, and hair that shows alternating light and dark bands. Serum albumin is 1.8 g/dL. Haemoglobin is 8.2 g/dL. Stool microscopy shows no parasites. Which of the following biochemical profiles is most consistent with this child's nutritional disorder?

Accepted Answer

B. Low serum albumin, low serum transferrin, low serum insulin-like growth factor-1, normal serum glucose

Answer

A. Low serum albumin, low serum retinol-binding protein, normal serum zinc, low serum transferrin with elevated serum copper

Answer

C. Low serum albumin, elevated blood urea nitrogen, high urine osmolality, low serum sodium

Answer

D. Low serum albumin, low serum calcium, elevated alkaline phosphatase, low serum phosphate

Question 2

What is a characteristic feature of Systemic Juvenile Idiopathic Arthritis?

Accepted Answer

RA factor is negative

Answer

Uveitis is a feature

Answer

It occurs after 16 years of age

Answer

NSAIDs are contraindicated

Question 3

An 8-year-old child has had abdominal pain and dark urine for 10 days. Physical examination shows blotchy purple skin lesions on the trunk and extremities. Urinalysis shows hematuria and proteinuria. Serologic test results are negative for myeloperoxidase-antineutrophil cytoplasmic antibody (MPO-ANCA) and proteinase 3-antineutrophil cytoplasmic antibody (PR3-ANCA). A skin biopsy specimen shows necrotizing vasculitis of small dermal vessels. A renal biopsy specimen shows immune complex deposition in glomeruli, with some IgA-rich immune complexes. Which of the following is the most likely diagnosis?

Accepted Answer

Henoch-Schonlein purpura

Answer

Giant cell arteritis

Answer

Polyarteritis nodosa

Answer

Takayasu arteritis

Question 4

A child presents with delayed separation of the umbilical cord, leukocytosis, Down syndrome, and recurrent infections. What is the most likely diagnosis?

Accepted Answer

Leukocyte Adhesion Deficiency

Answer

Neonatal Sepsis

Answer

Histiocytosis-X

Answer

All of the above

Question 5

A 5-year-old male child presents with a history of recurrent infections and rashes, as shown in the image. Routine blood investigations reveal thrombocytopenia. Which of the following diagnoses is most likely?

Accepted Answer

Wiskott Aldrich syndrome

Answer

Job syndrome

Answer

Measles

Answer

Henoch Schonlein purpura

Immunology and Allergies — MCQs

Immunology and Allergies — MCQs

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