Immunology and Allergies Practice Questions

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: Which antibody is not transmitted from mother to baby?

IgA antibodies. ***IgA antibodies*** - While IgA is found in breast milk and provides **passive immunity** to the infant's gastrointestinal tract, it is **not transferred across the placenta** to the fetus. - This antibody has a larger molecular structure and is primarily involved in **mucosal immunity**, making it unsuitable for transplacental transfer. *Diphtheria IgG antibodies* - **IgG antibodies**, including those for diphtheria, are actively transported across the **placenta** from mother to fetus during the third trimester. - This transfer provides the newborn with **passive immunity** against diphtheria during the first few months of life. *Tetanus IgG antibodies* - Similar to diphtheria IgG, **tetanus IgG antibodies** are efficiently transported across the **placenta** from mother to baby. - This offers crucial **passive protection** against tetanus, particularly important after birth. *Measles IgG antibodies* - **Measles IgG antibodies** from a vaccinated or previously infected mother cross the **placenta** to the fetus. - This maternal transfer provides temporary **passive immunity** to the newborn against measles.

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 condition is likely to develop in a child with a mother who has asthma?

Atopic dermatitis. ***Atopic dermatitis*** - **Atopic dermatitis** is strongly associated with a family history of **atopy**, which includes **asthma**, allergic rhinitis, and eczema. - Children of mothers with asthma have a significantly increased risk of developing atopic conditions due to **genetic predisposition** and shared immunological pathways. - This is part of the **atopic march** where children often develop atopic dermatitis first, followed by other atopic conditions. *SLE* - **Systemic lupus erythematosus (SLE)** is a systemic autoimmune disease not directly linked to a maternal history of asthma. - While it has a genetic component, it is distinct from the **atopic** disease spectrum. *Erythema multiforme* - **Erythema multiforme** is a hypersensitivity reaction typically triggered by infections (especially HSV) or medications. - It is not associated with maternal asthma or the atopic disease spectrum. - It presents with characteristic target lesions on skin and mucous membranes. *TEN* - **Toxic epidermal necrolysis (TEN)** is a severe, life-threatening skin reaction, most often drug-induced. - There is no known direct association between maternal asthma and the development of TEN in offspring.

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 has a rash. His family history is positive for asthma. What could be the most probable diagnosis?

Atopic dermatitis. ***Atopic dermatitis*** - The presence of a rash in a child with a family history of **asthma** strongly suggests atopic dermatitis, as it is part of the **atopic triad** (eczema, asthma, allergic rhinitis). - Atopic dermatitis often presents with **erythematous, pruritic patches** and plaques, commonly affecting flexural areas like the antecubital and popliteal fossae, as well as the face and neck in younger children. *Seborrheic dermatitis* - This condition typically presents with **greasy, yellowish scales** on an erythematous base, often affecting areas rich in sebaceous glands such as the scalp, face (nasolabial folds), and chest. - While it can occur in infants, it does not have the strong association with a family history of asthma seen in atopic dermatitis. *Allergic contact dermatitis* - This rash results from an **exposure to an allergen**, leading to a localized, erythematous, and pruritic eruption, often with vesicles or bullae, at the site of contact. - The history does not provide information about a specific allergen exposure, and while it could produce a similar-looking rash, the family history of asthma points more strongly to atopic diathesis. *Erysipelas* - Erysipelas is a superficial skin infection, usually caused by *Streptococcus pyogenes*, presenting as a **well-demarcated, intensely erythematous, warm, and painful rash** with a raised border. - This is an **acute bacterial infection** and would typically be accompanied by systemic symptoms like fever and chills, which are not mentioned in the child's presentation.

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.

Q: Polyarticular onset JRA involves more than how many joints?

4. ***4*** - **Polyarticular onset Juvenile Rheumatoid Arthritis (JRA)**, now often referred to as **Juvenile Idiopathic Arthritis (JIA)**, is defined by the involvement of **five or more joints** within the first six months of the disease. Therefore, "more than 4" correctly describes this threshold. - This subtype of JIA accounts for approximately 30% of all JIA cases and can be further classified into rheumatoid factor-positive and rheumatoid factor-negative forms. *3* - Involvement of **fewer than five joints** (i.e., four or fewer) within the first six months would classify the disease as **oligoarticular JIA**, a distinct and often milder subtype. - Oligoarticular JIA is the most common subtype and often affects large joints like the knees. *5* - While **five or more joints** is the diagnostic criterion for polyarticular JIA, stating "more than 5" would be incorrect as exactly five joints already falls within the polyarticular definition. - The threshold is **equal to or greater than five joints**, not strictly exceeding five. *6* - Specifying "more than 6" joints would exclude cases where 5 or 6 joints are involved, which are still considered polyarticular JIA. - The key diagnostic number is **five**, meaning "more than 4" encompasses the correct definition.

Q: At what age does clinically significant IgG production begin?

Around 6 months. ***Around 6 months*** - Maternal IgG levels, which provide **passive immunity**, decrease significantly by 3-6 months of age. - Infants begin to produce their own **clinically significant** levels of IgG around this time, coinciding with the "physiologic nadir" of IgG. *Around 1 year* - While IgG production continues to mature, significant production has already begun by 6 months to replace declining maternal antibodies. - By 1 year, the immune system is more robust, but the initial critical transition occurs earlier. *Around 2 years* - By this age, children generally have a robust adaptive immune response, and the period of vulnerability due to low IgG has passed. - This option is too late for the beginning of clinically significant IgG production. *Around 3 years* - This age is far past the point where children start producing their own significant levels of IgG. - The immune system is well-developed by 3 years, and initial IgG production started much earlier.

Question 1

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

Accepted Answer

Influenza

Answer

Yellow fever

Answer

MMR

Answer

DPT

Question 2

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 3

Which antibody is not transmitted from mother to baby?

Accepted Answer

IgA antibodies

Answer

Tetanus IgG antibodies

Answer

Diphtheria IgG antibodies

Answer

Measles IgG antibodies

Question 4

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 5

What condition is likely to develop in a child with a mother who has asthma?

Accepted Answer

Atopic dermatitis

Answer

SLE

Answer

Erythema multiforme

Answer

TEN

Question 6

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 7

A child has a rash. His family history is positive for asthma. What could be the most probable diagnosis?

Accepted Answer

Atopic dermatitis

Answer

Seborrheic dermatitis

Answer

Allergic contact dermatitis

Answer

Erysipelas

Question 8

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

Question 9

Polyarticular onset JRA involves more than how many joints?

Accepted Answer

4

Answer

5

Answer

3

Answer

6

Question 10

At what age does clinically significant IgG production begin?

Accepted Answer

Around 6 months

Answer

Around 1 year

Answer

Around 2 years

Answer

Around 3 years

Immunology and Allergies — MCQs

Immunology and Allergies — MCQs

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