Immunology and Allergies Practice Questions

Q: A 2-year-old child presents with recurrent infections, failure to thrive, and persistent diarrhea. The family history reveals a sibling who died from a similar illness. What is the most likely diagnosis?

Severe Combined Immunodeficiency. ***Severe Combined Immunodeficiency*** - **Recurrent infections**, **failure to thrive**, and **persistent diarrhea** in a young child, especially with a history of a sibling succumbing to a similar illness, are classic signs of **Severe Combined Immunodeficiency (SCID)**. - SCID results in a profound defect in both **T-cell and B-cell immunity**, leaving the child extremely vulnerable to opportunistic infections and leading to the observed clinical features. *Cystic Fibrosis* - While **failure to thrive** and **persistent diarrhea** (due to pancreatic insufficiency) can occur in cystic fibrosis, recurrent infections primarily involve the **respiratory tract** and are not usually indicative of a global immune deficiency like in SCID. - Absence of key features such as **meconium ileus** at birth, **steatorrhea**, or positive **sweat chloride test** makes this less likely. *Chronic Granulomatous Disease* - Patients with **Chronic Granulomatous Disease (CGD)** suffer from recurrent infections, but these are typically caused by **catalase-positive organisms** and manifest as **abscesses** and **granulomas**. - While it affects immune function, it does not typically present with the same spectrum of severe, persistent infections, failure to thrive, and diarrhea across all immune axes as seen in SCID. *HIV Infection* - Although **recurrent infections**, **failure to thrive**, and **diarrhea** are symptoms of pediatric **HIV infection**, the family history of a sibling dying from a similar illness strongly points towards an inherited genetic disorder like SCID rather than an acquired infection. - HIV typically presents with a more gradual decline in immune function rather than the profound deficiency seen early in life with SCID.

Q: A 2-year-old girl presents with a history of recurrent infections, eczema, and thrombocytopenia. What is the most likely diagnosis?

Wiskott-Aldrich syndrome. ***Wiskott-Aldrich syndrome*** - This syndrome is characterized by the classic triad of **recurrent infections, eczema, and thrombocytopenia** (low platelet count), often with small-sized platelets. - It is an **X-linked recessive disorder** caused by a mutation in the WASP gene, leading to defective immune cell function and platelet abnormalities. *Chediak-Higashi syndrome* - This condition is characterized by **recurrent pyogenic infections, partial albinism, peripheral neuropathy, and giant lysosomes** in phagocytes. - While it involves recurrent infections, the absence of **partial albinism** and presence of thrombocytopenia with eczema make it less likely. *Chronic granulomatous disease* - Patients with this disease suffer from recurrent severe bacterial and fungal infections due to a defect in **phagocyte oxidative burst**, leading to the inability to kill certain microbes. - It is not typically associated with **eczema** or primary **thrombocytopenia**, distinguishing it from the presented case. *Severe combined immunodeficiency* - This is a very severe primary immunodeficiency characterized by significant defects in both **T-cell and B-cell immunity**, leading to opportunistic infections, failure to thrive, and chronic diarrhea. - While it causes recurrent infections, **eczema** and **thrombocytopenia** are not defining features as they are in Wiskott-Aldrich syndrome.

Q: What should be the correct treatment for a 14-year-old child with newly diagnosed Juvenile Rheumatoid Arthritis?

DMARDs with a short course of steroids. ***DMARDs with a short course of steroids*** - For **newly diagnosed rheumatoid arthritis** in children (juvenile idiopathic arthritis), the primary goal is to **control inflammation** and prevent joint damage with **disease-modifying antirheumatic drugs (DMARDs)**. - A **short course of corticosteroids** is often used as a **bridging therapy** to rapidly reduce inflammation while the DMARDs take effect. - This approach ensures **early aggressive treatment** to prevent joint damage while minimizing long-term steroid exposure. *Incorrect: Only NSAIDs* - **NSAIDs** alone provide **symptomatic relief** but do not alter the course of the disease or prevent joint damage in rheumatoid arthritis. - Relying solely on NSAIDs can lead to **progressive joint erosion** and functional impairment. *Incorrect: DMARDs after initial treatment with NSAIDs* - While NSAIDs can be used for initial symptom control, delaying **DMARD initiation** is generally not recommended as it allows for continued joint inflammation and potential damage. - Early and aggressive treatment with DMARDs is crucial for **optimizing long-term outcomes** and preserving joint function. *Incorrect: Monotherapy with TNF inhibitors* - **TNF inhibitors** are potent **biologic DMARDs** and are typically considered for patients who have **failed conventional DMARDs** (e.g., methotrexate). - They are not usually the **first-line monotherapy** for treatment-naive rheumatoid arthritis due to their cost, potential side effects, and the availability of other effective options. *Incorrect: Long-term high-dose corticosteroid therapy* - **Prolonged corticosteroid use** at high doses is associated with significant side effects including growth suppression, osteoporosis, increased infection risk, and cushingoid features. - While steroids are useful as **bridging therapy** for a short duration, long-term high-dose use is avoided in pediatric patients whenever possible.

Q: Delayed umbilical cord detachment with leukocytosis is seen in?

Leukocyte adhesion deficiency (LAD). ***Leukocyte adhesion deficiency (LAD)*** - **Delayed umbilical cord detachment** (beyond 3 weeks) is a classic hallmark of LAD due to impaired neutrophil migration to the umbilical stump for normal wound healing. - **Marked leukocytosis** with neutrophilia (often >20,000-30,000/μL) is characteristic, as neutrophils cannot extravasate from blood vessels to sites of infection. - Caused by defects in **CD18 integrin molecules** (LAD-1) or other adhesion molecules, preventing neutrophil adherence and migration. *Chronic granulomatous disease* - Patients suffer from recurrent bacterial and fungal infections due to defective **phagocyte oxidative burst** and inability to kill catalase-positive organisms. - Does **not** present with delayed cord detachment; cord separation occurs normally. - Characterized by granuloma formation and infections with specific organisms (Staphylococcus, Aspergillus, Serratia). *Severe combined immunodeficiency (SCID)* - Severe defect in both **T-cell and B-cell immunity** leading to recurrent opportunistic infections, chronic diarrhea, and failure to thrive. - Does **not** present with delayed umbilical cord detachment or characteristic leukocytosis. - Typically presents in early infancy with severe infections. *Chediak-Higashi syndrome* - Rare autosomal recessive disorder with **partial albinism**, recurrent pyogenic infections, and progressive neurological dysfunction. - Features neutropenia or normal neutrophil counts, **not leukocytosis**. - Does **not** have delayed cord detachment as a characteristic feature.

Q: Historically, which vaccine required special precautions in children with egg allergies?

Influenza. ***Influenza*** - Historically, influenza vaccines were produced in **embryonated chicken eggs**, leading to concerns about allergic reactions in individuals with egg allergies. - While current recommendations often allow vaccination for most egg-allergic individuals, **special precautions** were previously advised, including graded administration or use of egg-free formulations. - Modern guidelines from AAP and CDC have relaxed these restrictions, but the historical concern was significant. *Yellow fever* - While the **yellow fever vaccine** is also produced in embryonated chicken eggs and does carry egg allergy precautions, it is less commonly administered in routine pediatric practice compared to influenza vaccine. - The question specifically asks about historical concerns in **children**, making influenza the more relevant answer due to its widespread annual use in pediatric populations. - Yellow fever vaccination is primarily for travelers to endemic areas. *MMR* - The **MMR (Measles, Mumps, Rubella) vaccine** is grown in chick embryo fibroblast cultures but contains negligible amounts of egg protein, so it generally does not require special precautions for children with egg allergies. - Allergic reactions to MMR are usually due to components other than residual egg protein, such as gelatin or neomycin. *DPT* - The **DPT (Diphtheria, Pertussis, Tetanus) vaccine** is not manufactured using egg-based cultures and therefore has no historical or current association with egg allergies. - Egg allergy is not a contraindication or precaution for DPT vaccination.

Q: A male child presented with arthralgia and abdominal pain. On examination, there was palpable purpura over the lower limbs. There is a past history of upper respiratory tract infection prior to the onset of presenting symptoms. Which of the following is the treatment for this condition?

Glucocorticoids. ***Glucocorticoids*** - The constellation of **arthralgia**, **abdominal pain**, and **palpable purpura** following an **upper respiratory tract infection** in a child is highly suggestive of **Henoch-Schönlein purpura (HSP)**, now known as **IgA vasculitis**. - **Glucocorticoids** are indicated in HSP for severe symptoms like significant abdominal pain, gastrointestinal bleeding, or painful arthralgia, all of which this patient demonstrates. - While HSP often resolves spontaneously with supportive care, this patient's presentation with both arthralgia and abdominal pain warrants glucocorticoid therapy. *Azathioprine* - **Azathioprine** is an immunosuppressant typically used for conditions like rheumatoid arthritis, IBD, or organ transplant rejection. - It is not a first-line treatment for the acute management of **IgA vasculitis**, which typically responds to supportive care or short courses of steroids for severe symptoms. *Methotrexate* - **Methotrexate** is a disease-modifying antirheumatic drug (DMARD) used in conditions such as rheumatoid arthritis, psoriasis, and certain cancers. - It does not have a role in the acute treatment of uncomplicated **IgA vasculitis** based on the described symptoms. *Cyclosporine* - **Cyclosporine** is a potent immunosuppressant used in severe autoimmune conditions or to prevent organ rejection. - While it may be considered in very severe, refractory cases of **IgA vasculitis** with significant renal involvement, it is not the initial treatment for the symptoms presented.

Q: A child presents with fever, photosensitivity, and a rash that spares the nasolabial fold. What is the most likely diagnosis?

Systemic Lupus Erythematosus (SLE). ***Systemic Lupus Erythematosus (SLE)*** - The classic **malar rash** of SLE often spares the **nasolabial folds**, differentiating it from other facial rashes. - **Fever** and **photosensitivity** are common systemic symptoms and triggers for SLE flares. - This presentation with systemic symptoms (fever) plus the characteristic rash pattern is pathognomonic for SLE. *Polymorphous light eruption (PLE)* - While PLE can cause a photosensitive rash, it typically presents after UV exposure and lacks the systemic symptoms like **fever** seen in this patient. - The rash distribution in PLE is often more polymorphic and not specifically described as sparing the nasolabial folds. *Localized lupus erythematosus* - This is a vague term that doesn't capture the **systemic involvement** indicated by fever and widespread photosensitivity. - **Cutaneous lupus** (including discoid lupus) typically presents with chronic, scarring plaques rather than acute malar rash. - The presence of fever strongly suggests systemic rather than localized disease. *Cutaneous tuberculosis* - Cutaneous tuberculosis presents with specific skin lesions like **lupus vulgaris** or **scrofuloderma**, which are chronic and destructive. - It does not typically manifest with acute fever, photosensitivity, and an erythematous rash covering the face with nasolabial sparing.

Q: What is the most common cause of death in children with systemic lupus erythematosus (SLE)?

Infections due to immunosuppression. ***Infections due to immunosuppression*** - **Immunosuppressive therapy**, including corticosteroids and other agents used to manage SLE, significantly increases the risk of **severe infections**. - Children with SLE often have a compromised immune system due to the disease itself and its treatment, making them vulnerable to life-threatening bacterial, viral, and fungal infections. *Lupus nephritis* - While **lupus nephritis** is a major cause of morbidity and can lead to end-stage renal disease, it is generally less common as the immediate cause of death compared to severe infections, especially in the context of effective treatments. - Renal failure can be a long-term complication, but acute infectious complications often pose a more immediate threat to life. *Cardiovascular complications* - **Cardiovascular complications**, such as atherosclerosis and premature coronary artery disease, are significant long-term concerns in SLE patients, including children, but they typically manifest later in life. - While they contribute to long-term mortality, they are less likely to be the most common cause of death in the pediatric population compared to acute infections. *Pulmonary hemorrhage* - **Pulmonary hemorrhage** is a rare but severe manifestation of SLE, causing acute respiratory distress and high mortality when it occurs. - However, its overall incidence is low compared to the widespread issue of infection in immunosuppressed SLE patients.

Q: A child is suffering from recurrent chronic infections with encapsulated bacteria due to a deficiency of which immunoglobulin G subclass?

IgG2. ***IgG2*** - **IgG2 deficiency** is primarily associated with an impaired immune response to **polysaccharide antigens**, which comprise the **capsules of encapsulated bacteria**. - Individuals with this deficiency are prone to **recurrent infections** from encapsulated bacteria such as ***Streptococcus pneumoniae***, ***Haemophilus influenzae***, and ***Neisseria meningitidis***. - This is the most clinically relevant IgG subclass deficiency for encapsulated bacterial infections. *IgG1* - **IgG1** is the most abundant IgG subclass (approximately 60-70% of total IgG) and is crucial for immune responses against **protein antigens** and **toxins**. - While IgG1 deficiency can occur, it would lead to a broader range of infections beyond just encapsulated bacteria. *IgG3* - **IgG3** is involved in responses to **protein antigens** and is highly effective in activating the **classical complement pathway**. - Deficiencies are rare and typically involve different types of infections rather than specifically encapsulated bacteria. *IgG4* - **IgG4** is the least abundant subclass and is known for its **anti-inflammatory properties** and ability to block allergic reactions. - Its deficiency is typically not associated with recurrent bacterial infections with encapsulated pathogens.

Question 1

A 2-year-old child presents with recurrent infections, failure to thrive, and persistent diarrhea. The family history reveals a sibling who died from a similar illness. What is the most likely diagnosis?

Accepted Answer

Severe Combined Immunodeficiency

Answer

Cystic Fibrosis

Answer

Chronic Granulomatous Disease

Answer

HIV Infection

Question 2

A 10-year-old boy presents with recurrent sinopulmonary infections, eczema, and thrombocytopenia. What is the most likely diagnosis?

Accepted Answer

Wiskott-Aldrich syndrome

Answer

DiGeorge syndrome

Answer

Bruton's agammaglobulinemia

Answer

Chronic granulomatous disease

Question 3

A 2-year-old girl presents with a history of recurrent infections, eczema, and thrombocytopenia. What is the most likely diagnosis?

Accepted Answer

Wiskott-Aldrich syndrome

Answer

Chediak-Higashi syndrome

Answer

Chronic granulomatous disease

Answer

Severe combined immunodeficiency

Question 4

What should be the correct treatment for a 14-year-old child with newly diagnosed Juvenile Rheumatoid Arthritis?

Accepted Answer

DMARDs with a short course of steroids

Answer

Only NSAIDs

Answer

DMARDs after initial treatment with NSAIDs

Answer

Monotherapy with TNF inhibitors

Answer

Long-term high-dose corticosteroid therapy

Question 5

Delayed umbilical cord detachment with leukocytosis is seen in?

Accepted Answer

Leukocyte adhesion deficiency (LAD)

Answer

Chronic granulomatous disease

Answer

Severe combined immunodeficiency

Answer

Chediak-Higashi syndrome

Question 6

Historically, which vaccine required special precautions in children with egg allergies?

Accepted Answer

Influenza

Answer

Yellow fever

Answer

MMR

Answer

DPT

Question 7

A male child presented with arthralgia and abdominal pain. On examination, there was palpable purpura over the lower limbs. There is a past history of upper respiratory tract infection prior to the onset of presenting symptoms. Which of the following is the treatment for this condition?

Accepted Answer

Glucocorticoids

Answer

Azathioprine

Answer

Methotrexate

Answer

Cyclosporine

Question 8

A child presents with fever, photosensitivity, and a rash that spares the nasolabial fold. What is the most likely diagnosis?

Accepted Answer

Systemic Lupus Erythematosus (SLE)

Answer

Localized lupus erythematosus

Answer

Polymorphous light eruption (PLE)

Answer

Cutaneous tuberculosis

Question 9

What is the most common cause of death in children with systemic lupus erythematosus (SLE)?

Accepted Answer

Infections due to immunosuppression

Answer

Lupus nephritis

Answer

Cardiovascular complications

Answer

Pulmonary hemorrhage

Question 10

A child is suffering from recurrent chronic infections with encapsulated bacteria due to a deficiency of which immunoglobulin G subclass?

Accepted Answer

IgG2

Answer

IgG1

Answer

IgG3

Answer

IgG4

Immunology and Allergies — MCQs

Immunology and Allergies — MCQs

On this page

Practice by Chapter

Want unlimited practice?