Immunology and Allergies — MCQs

Immunology and Allergies Indian Medical PG Practice Questions and MCQs

Question 101: A 2-year-old child presents with recurrent episodes of abdominal pain, palpable purpura on the buttocks, and arthritis. What is the most likely diagnosis?

A. Henoch-Schönlein purpura (Correct Answer)
B. Kawasaki disease
C. Systemic lupus erythematosus
D. Juvenile idiopathic arthritis

Explanation: **Correct: Henoch-Schönlein purpura** - The classic triad of **palpable purpura**, arthritis, and abdominal pain in a child is highly characteristic of **Henoch-Schönlein purpura** (HSP), a form of small-vessel vasculitis. - The disease is also associated with **renal involvement** (hematuria/proteinuria) in a significant percentage of cases, which would further support the diagnosis. - The **buttocks and lower extremities** are the typical distribution sites for the purpuric rash in HSP. *Incorrect: Kawasaki disease* - Characterized by **fever** (mandatory criterion), conjunctivitis, changes in oral mucosa (strawberry tongue), cervical lymphadenopathy, rash, and extremity changes, which are not described in the child's presentation. - The primary concern in Kawasaki disease is the risk of **coronary artery aneurysms**. - Does not typically present with palpable purpura or abdominal pain. *Incorrect: Systemic lupus erythematosus* - While it can cause **arthritis** and skin manifestations, lupus typically presents with a broader range of systemic symptoms like malar rash, photosensitivity, serositis, and renal disease. - SLE is **uncommon in toddlers** (peak age 15-45 years), making it less likely in a 2-year-old. - The purpura in SLE is usually not palpably elevated as described in HSP. *Incorrect: Juvenile idiopathic arthritis* - Primarily involves **chronic joint inflammation** (arthritis) lasting for at least 6 weeks in children under 16 years. - It does not typically present with **palpable purpura** or acute abdominal pain as a primary feature. - Would not explain the characteristic skin findings seen in this case.

Question 102: A child with recurrent infections, eczema, and thrombocytopenia is diagnosed with Wiskott-Aldrich Syndrome. Which therapeutic approach is the most appropriate for long-term management?

A. Bone marrow transplantation (Correct Answer)
B. Chronic immunoglobulin therapy
C. Surgical removal of the spleen
D. Frequent platelet transfusions

Explanation: ***Bone marrow transplantation*** - **Hematopoietic stem cell transplantation (HSCT/BMT)** is the only curative treatment for **Wiskott-Aldrich Syndrome (WAS)** as it corrects the underlying stem cell defect caused by WASP gene mutation. - It addresses all three major manifestations: **immunodeficiency**, **eczema**, and **thrombocytopenia**, significantly improving long-term outcomes and survival. - HLA-matched sibling or unrelated donor transplantation is the definitive standard of care for eligible patients. *Chronic immunoglobulin therapy* - **Immunoglobulin therapy (IVIG)** helps manage recurrent infections by providing passive immunity but does not correct the underlying immune defect or the **thrombocytopenia**. - It is a supportive measure for infection prophylaxis, not a definitive long-term cure for all aspects of WAS. *Surgical removal of the spleen* - **Splenectomy** is generally **contraindicated** in WAS as it significantly worsens the risk of severe infections due to underlying immunodeficiency. - While it might theoretically improve platelet counts by reducing sequestration, it does not address the primary immune defect, qualitative platelet dysfunction, or eczema. *Frequent platelet transfusions* - **Platelet transfusions** are reserved for acute bleeding episodes or severe thrombocytopenia but do not provide a long-term solution. - They carry risks of **alloimmunization** and **transfusion reactions**, and do not correct the qualitative platelet defects or immune dysfunction inherent to WAS.

Question 103: A child with a known peanut allergy accidentally ingests a food containing peanuts and develops urticaria, vomiting, and wheezing within minutes. What is the first-line treatment?

A. Oral antihistamines
B. Subcutaneous epinephrine
C. Intramuscular epinephrine (Correct Answer)
D. High-dose corticosteroids

Explanation: ***Intramuscular epinephrine*** - This patient is experiencing **anaphylaxis**, characterized by rapid-onset **urticaria**, **vomiting** (gastrointestinal involvement), and **wheezing** (respiratory involvement). - **Epinephrine** is the **first-line treatment** for anaphylaxis due to its alpha-1 agonist effects (vasoconstriction to counteract hypotension and reduce angioedema) and beta-2 agonist effects (bronchodilation to relieve wheezing). Intramuscular administration ensures rapid absorption and systemic effect. *Oral antihistamines* - While antihistamines can help manage cutaneous symptoms like **urticaria** and **itching**, they do not address the life-threatening respiratory or cardiovascular symptoms of anaphylaxis. - They are considered **adjunctive therapy** for mild allergic reactions but are not sufficient as first-line treatment for anaphylaxis. *Subcutaneous epinephrine* - **Subcutaneous administration** is historical and **not recommended** for anaphylaxis because it has a slower and less predictable absorption compared to intramuscular injection. - The delay in onset of action can be critical in a rapidly progressing anaphylactic reaction. *High-dose corticosteroids* - **Corticosteroids** act too slowly to be useful as a primary treatment for acute anaphylaxis, as their effects take several hours to manifest. - They are used as **adjunctive therapy** to prevent protracted or biphasic reactions, but not for the initial management of acute symptoms.

Question 104: A 4-month-old infant with a history of eczema develops wheezing and difficulty breathing after breastfeeding. What should be the initial approach to managing this acute presentation?

A. Administer an epinephrine injection (Correct Answer)
B. Perform skin allergy testing
C. Start a hypoallergenic formula
D. Prescribe oral antihistamines

Explanation: ***Administer an epinephrine injection*** - The combination of **wheezing**, **difficulty breathing**, and a history of **eczema** after breastfeeding strongly suggests a severe allergic reaction (anaphylaxis) to a component in breast milk or something the mother consumed. - **Epinephrine** is the first-line treatment for **anaphylaxis** and should be administered immediately in this acute, life-threatening situation. *Perform skin allergy testing* - Skin allergy testing is a diagnostic procedure to identify allergens but is **not an initial treatment** for an acute, severe allergic reaction. - This test should be performed in a controlled setting after the acute symptoms have been managed. *Start a hypoallergenic formula* - While switching to a **hypoallergenic formula** might be a dietary consideration if a milk protein allergy is suspected, it is not the immediate intervention for acute respiratory distress. - This is a long-term management strategy, not an emergency treatment. *Prescribe oral antihistamines* - **Oral antihistamines** can help manage mild allergic symptoms like hives or itching but are **ineffective** in severe reactions involving the respiratory system or cardiovascular collapse. - They do not address the underlying physiological changes of anaphylaxis, such as **bronchoconstriction** and **vasodilation**.

Question 105: A 3-year-old child presents with a history of recurrent infections, chronic diarrhea, and failure to thrive. On examination, the lymph nodes and tonsils are absent. What is the most likely diagnosis?

A. HIV Infection
B. Cystic Fibrosis
C. Severe Combined Immunodeficiency (Correct Answer)
D. Chronic Granulomatous Disease

Explanation: ***Severe Combined Immunodeficiency*** - The combination of **recurrent infections** (due to severe impairment of both T and B lymphocyte function), **chronic diarrhea**, **failure to thrive**, and **absent lymph nodes and tonsils** (indicating severe lymphoid hypoplasia) is highly characteristic of SCID. - Patients with SCID lack functional **T cells** and often **B cells**, making them extremely vulnerable to opportunistic infections and leading to the observed clinical features. - In severe SCID, **profound lymphopenia** leads to marked lymphoid hypoplasia, which can manifest as absent or extremely small lymph nodes and tonsils—a key clinical finding that helps differentiate SCID from other immunodeficiencies. *HIV Infection* - While HIV can cause recurrent infections, diarrhea, and failure to thrive, **absent lymph nodes and tonsils** are not typical. Instead, lymphadenopathy (swollen lymph nodes) is often seen in early or chronic HIV infection. - The primary defect in HIV is in **CD4+ T cells**, but lymphoid organs are generally present, though their structure may be altered. *Cystic Fibrosis* - Characterized by **chronic diarrhea** (due to pancreatic insufficiency) and **failure to thrive**, but recurrent infections primarily involve the **respiratory tract** (e.g., recurrent pneumonia). - It does **not typically involve immunodeficiency** or absent lymphoid tissue like lymph nodes and tonsils. *Chronic Granulomatous Disease* - Patients experience **recurrent bacterial and fungal infections** due to a defect in phagocyte oxidative burst, leading to defective killing of pathogens. - While infections can be severe, it does **not typically present with absent lymph nodes and tonsils** or the severe T-cell mediated immunodeficiency seen in SCID.

Question 106: A 7-year-old child presents with recurrent bacterial infections and delayed separation of the umbilical cord. Laboratory results show high white blood cell counts and absent pus formation. What is the likely diagnosis?

A. Chronic granulomatous disease
B. Leukocyte adhesion deficiency (Correct Answer)
C. Chediak-Higashi syndrome
D. Severe combined immunodeficiency

Explanation: ***Leukocyte adhesion deficiency*** - The combination of **recurrent bacterial infections**, **delayed umbilical cord separation**, and the striking absence of **pus formation** despite high white blood cell counts is a classic presentation. - This condition is caused by a defect in **integrins** (specifically CD18) on phagocytes, impairing their ability to adhere to vascular endothelium and extravasate into tissues. *Chronic granulomatous disease* - Characterized by recurrent infections with **catalase-positive organisms** and granuloma formation, usually presenting as abscesses and organomegaly. - While it involves recurrent infections, it does not typically present with delayed umbilical cord separation or absent pus formation as a primary diagnostic clue. *Chediak-Higashi syndrome* - This syndrome presents with **partial oculocutaneous albinism**, recurrent pyogenic infections, and neurologic abnormalities due to defective lysosomal trafficking. - While it involves immunodeficiency and recurrent infections, the clinical picture does not include delayed umbilical cord separation or the characteristic lack of pus. *Severe combined immunodeficiency* - Presents with severe, recurrent infections, **failure to thrive**, and chronic diarrhea, affecting both T-cell and B-cell immunity. - Though it causes severe infections, it is distinguished by a profound lack of functional lymphocytes and does not typically feature delayed umbilical cord separation or impaired pus formation due to neutrophil extravasation issues.

Question 107: A 7-year-old child presents with fever, abdominal pain, and a rash on the lower extremities. Laboratory tests show elevated inflammatory markers. What is the most likely diagnosis?

A. Systemic Lupus Erythematosus
B. Henoch-Schönlein Purpura (Correct Answer)
C. Juvenile Idiopathic Arthritis
D. Kawasaki Disease

Explanation: ***Henoch-Schönlein Purpura*** - This condition is characterized by a classic triad of **palpable purpura** (often on the lower extremities), **abdominal pain**, and **arthritis**, sometimes preceded by a fever. - It is an **IgA-mediated vasculitis** predominantly affecting children, with elevated inflammatory markers often present. *Systemic Lupus Erythematosus* - SLE presents with a wide range of symptoms, but a characteristic **malar rash**, photosensitivity, and kidney involvement are common, rather than a purpuric rash on the lower extremities as the initial presentation in a child. - While fever and abdominal pain can occur, the specific combination with a palpable purpuric rash points away from SLE. *Juvenile Idiopathic Arthritis* - JIA is primarily characterized by **chronic arthritis** (joint inflammation) lasting at least 6 weeks in children under 16 years. - While fever can be present in systemic JIA, a palpable purpuric rash and prominent abdominal pain are not typical features. *Kawasaki Disease* - Kawasaki disease typically presents with **high fever** for at least 5 days, **conjunctivitis**, **oral mucosal changes** (strawberry tongue), **rash** (often polymorphous but not usually purpuric), and **lymphadenopathy**. - While fever and rash are present, the rash in this case is described as purpuric, and abdominal pain is not a primary diagnostic criterion for Kawasaki disease.

Question 108: A 12-month-old infant presents with recurrent infections, eczema, and thrombocytopenia. Genetic testing reveals an X-linked recessive disorder. What is the most likely diagnosis?

A. Severe combined immunodeficiency
B. Chronic granulomatous disease
C. Wiskott-Aldrich syndrome (Correct Answer)
D. X-linked agammaglobulinemia

Explanation: ***Wiskott-Aldrich syndrome*** - This syndrome is characterized by the classic triad of **recurrent infections, eczema, and thrombocytopenia**, making it the most likely diagnosis. - It is an **X-linked recessive disorder** caused by mutations in the WAS gene, leading to defective platelet function and immune dysregulation. *Severe combined immunodeficiency* - While it causes **recurrent severe infections** and can be X-linked, it does not typically present with **eczema and thrombocytopenia** as prominent features. - Infants with SCID usually fail to thrive and present with earlier, more severe opportunistic infections. *Chronic granulomatous disease* - This condition is characterized by recurrent infections with catalase-positive organisms and **granuloma formation**, often affecting the skin, lungs, and lymph nodes. - It does not primarily present with **eczema or thrombocytopenia**. *X-linked agammaglobulinemia* - Characterized by a severe deficiency in B cells and **antibody production**, leading to recurrent bacterial infections. - The disease does not typically involve **eczema or thrombocytopenia**.

Question 109: A 4-year-old boy presents with recurrent infections and failure to thrive. Laboratory investigations reveal periodic episodes of severe neutropenia occurring at regular intervals. What is the most likely diagnosis?

A. Chronic granulomatous disease
B. Wiskott-Aldrich syndrome
C. Severe combined immunodeficiency
D. Cyclic neutropenia (Correct Answer)

Explanation: ***Cyclic neutropenia*** - This condition is characterized by **periodic oscillations in neutrophil counts**, leading to recurring episodes of severe neutropenia, which explains the recurrent infections. - The **failure to thrive** can be a consequence of chronic or recurrent infections and inflammation associated with the neutropenic phases. *Chronic granulomatous disease* - This disorder primarily involves a defect in the **phagocytes' ability to produce reactive oxygen species**, making them unable to kill certain bacteria and fungi, leading to recurrent severe infections. - While it causes recurrent infections, the hallmark is the formation of **granulomas**, and it doesn't typically present with severe neutropenia as the primary hematological abnormality. *Severe combined immunodeficiency* - This condition involves a profound defect in both **T and B lymphocyte function**, leading to severe and life-threatening infections from a broad range of pathogens. - While it causes severe infections and failure to thrive, the defining feature is **lymphopenia** and profound immune dysfunction, not recurrent (cyclic) neutropenia as the primary hematological defect. *Wiskott-Aldrich syndrome* - This is an **X-linked immunodeficiency** characterized by a triad of **recurrent infections, eczema, and thrombocytopenia** (low platelet count). - While it causes recurrent infections and can lead to failure to thrive, severe neutropenia is not a characteristic feature; rather, **thrombocytopenia** is the prominent hematological abnormality.

Question 110: A 2-year-old child presents with recurrent respiratory infections and chronic diarrhea. Examination reveals failure to thrive and an absent thymic shadow on chest X-ray. What is the most likely diagnosis?

A. Severe combined immunodeficiency (Correct Answer)
B. Wiskott-Aldrich syndrome
C. Kawasaki disease
D. Cystic fibrosis

Explanation: ***Severe combined immunodeficiency*** - **Recurrent respiratory infections**, **chronic diarrhea**, **failure to thrive**, and an **absent thymic shadow** are classic presentations of SCID due to profound T-cell dysfunction. - The absence of a thymic shadow indicates a lack of T-cell maturation and development, a hallmark of SCID. *Kawasaki disease* - This is an **acute vasculitis** primarily affecting young children, characterized by fever, rash, conjunctivitis, oral changes, and lymphadenopathy, not recurrent infections or an absent thymic shadow. - It primarily affects the cardiovascular system, leading to potential **coronary artery aneurysms**, and does not involve immunodeficiency. *Wiskott-Aldrich syndrome* - Characterized by the triad of **eczema**, **thrombocytopenia** (leading to bleeding issues), and **recurrent infections**. - While recurrent infections are present, the hallmark features of severe **thrombocytopenia** and **eczema** are not mentioned, nor is an absent thymic shadow a typical finding. *Cystic fibrosis* - Primarily affects the **exocrine glands**, leading to thick, sticky mucus that obstructs airways and digestive tracts, causing recurrent pulmonary infections and **malabsorption leading to failure to thrive**. - Although recurrent respiratory infections and failure to thrive are consistent, **chronic diarrhea** in CF is due to pancreatic insufficiency, and an **absent thymic shadow** is not a feature of CF.

Practice by Chapter

Development of Immune System

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Primary Immunodeficiency Disorders

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Secondary Immunodeficiency Disorders

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Allergic Rhinitis

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Asthma in Children

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Atopic Dermatitis

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Food Allergies

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Drug Allergies

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Anaphylaxis

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Urticaria and Angioedema

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Autoimmune Disorders

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Immunotherapy

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