Immunology and Allergies Practice Questions

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: Most supportive laboratory investigation for Henoch-Schönlein purpura is -

Serum IgA levels. ***Serum IgA levels*** - **Henoch-Schönlein purpura (HSP)** is an **IgA vasculitis**, and elevated serum IgA levels are characteristic, although not diagnostic on their own. - The disease involves **IgA deposition** in small blood vessels, particularly in the skin, kidneys, and gastrointestinal tract. *C-reactive protein (CRP) levels* - CRP is a general **marker of inflammation**, which can be elevated in many conditions, including HSP. - It is **not specific to HSP** and does not help differentiate it from other inflammatory disorders. *Renal biopsy* - A renal biopsy can confirm **IgA nephropathy** with characteristic IgA deposition, which often occurs in HSP. - However, it is an **invasive procedure** and not the **most supportive laboratory investigation** for initial diagnosis compared to serum IgA, particularly when considering the broader clinical picture of HSP. *DTPA scan* - A **DTPA (diethylene triamine pentaacetic acid) scan** is a nuclear medicine test used to assess **renal function** and blood flow. - It is used to evaluate **renal complications** but is not a diagnostic tool for HSP itself.

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.

Q: Most common cause of death in SLE in children

Anemia and infections. ***Anemia and infections*** - **Infections** are a leading cause of death in pediatric SLE patients, often due to immunosuppression from the disease itself or its treatment. Although pediatric Systemic Lupus Erythematosus (SLE) is not a primary immune deficiency, the susceptibility to encapsulated bacteria and recurrent infections seen in primary B- and T-lymphocyte deficiencies mirrors the infection risks managed in these patients [1]. - **Anemia** can contribute to overall morbidity and mortality, although it is less directly a cause of death than severe infections or organ failure. *Lupus nephritis* - While **lupus nephritis** is a common and severe manifestation of SLE in children and a major cause of morbidity, particularly long-term kidney failure, it is not the most frequent immediate cause of death. - Advancements in treatment for nephritis have improved prognosis, shifting the leading cause of mortality to other factors. *Lupus cerebritis* - **Lupus cerebritis** (neuropsychiatric SLE) can be life-threatening, causing seizures, stroke, or psychosis, but it is less common as the primary cause of death compared to infections. - Its presence usually indicates severe disease requiring intensive treatment, but not the most common direct cause of death. *Libman sacks endocarditis* - **Libman-Sacks endocarditis** involves sterile vegetations on heart valves and is a known complication of SLE, but it rarely causes acute mortality in children. - It is more often associated with chronic complications like valvular dysfunction or a source of emboli rather than being the most common cause of death.

Q: In which of the following immunodeficiencies is this chest X-ray finding usually seen?

Hyper IgE syndrome. ***Hyper IgE syndrome*** - This syndrome is characterized by **recurrent staphylococcal skin abscesses**, **recurrent sinusitis**, and **pneumonia with pneumatocele formation**, which can appear as a cystic lesion on a chest X-ray. - Patients often present with **eczema**, **coarse facial features**, and notoriously high levels of **serum IgE**. *Wiskott-Aldrich syndrome* - This is an X-linked recessive disorder characterized by **eczema**, **thrombocytopenia** (leading to petechiae and bleeding), and **immunodeficiency** (recurrent infections). - Chest X-rays typically show complications of infections rather than pneumatocele formation specifically. *Di George syndrome* - This is a developmental defect of the **third and fourth pharyngeal pouches**, leading to **T-cell deficiency** (thymic hypoplasia), **hypocalcemia** (parathyroid hypoplasia), and **congenital heart defects**. - Chest X-ray findings might include a **small or absent thymic shadow** and cardiomegaly due to heart defects, not pneumatoceles. *Chediak Higashi syndrome* - This is an autosomal recessive disorder affecting **lysosomal trafficking**, characterized by **partial oculocutaneous albinism**, **recurrent pyogenic infections**, and **neurological abnormalities**. - Recurrent infections can occur, but the hallmark chest X-ray finding of **pneumatocele formation** is not typical of this syndrome.

Q: Which of the following is a characteristic symptom of Henoch-Schönlein Purpura?

Gastrointestinal bleeding. ***Gastrointestinal bleeding*** - **Gastrointestinal symptoms**, including bleeding, are common in **Henoch-Schönlein Purpura (HSP)** due to **IgA deposition** in the gut vasculature, leading to inflammation and hemorrhage. - Patients may experience colicky abdominal pain, nausea, vomiting, and bloody stools. *Low platelet count* - HSP is primarily a **vasculitis**, not a primary platelet disorder; therefore, patients typically have a **normal platelet count** [1]. - **Thrombocytopenia** would suggest a different diagnosis, such as **idiopathic thrombocytopenic purpura (ITP)** or another coagulation disorder. *Bleeding in the brain* - While a very rare complication, **intracranial hemorrhage** is not a characteristic or common symptom of HSP. - Most bleeding manifestations in HSP are related to the **skin**, **gut**, and sometimes **kidneys**. *Purpuric rash on buttocks and legs* - A **palpable purpuric rash** on the **buttocks and lower extremities** is indeed a hallmark symptom of HSP, but it is a skin manifestation, not a type of bleeding, and the question asks about a characteristic bleeding symptom. - This rash results from **leukocytoclastic vasculitis** with **IgA deposition** in small blood vessels [1].

Q: All are features of Wiskott-Aldrich syndrome, except which of the following?

Decreased IgA level. ***Decreased IgA level*** - Wiskott-Aldrich syndrome typically presents with **elevated IgA levels**, not decreased. - The characteristic humoral abnormalities include **low IgM** (most characteristic), **elevated IgA**, and **elevated IgE**. - IgG levels are variable (normal, elevated, or may decrease with disease progression). *Decreased IgM level* - This is the **most characteristic immunological feature** of Wiskott-Aldrich syndrome, contributing to susceptibility to encapsulated bacteria. - The defect in antibody production, particularly **IgM response to polysaccharide antigens**, is a hallmark of the disease. *Elevated IgE level* - High IgE levels are a common finding in Wiskott-Aldrich syndrome, often contributing to **eczema** and allergic manifestations. - This elevated IgE is part of the characteristic immunoglobulin pattern in WAS. *Decreased ratio of CD4 and CD8 cells* - This reflects **progressive T-cell dysfunction**, a central component of Wiskott-Aldrich syndrome. - Patients experience **gradual T-cell depletion** with decreased CD4/CD8 ratio, leading to impaired cell-mediated immunity.

Q: Which of the following statements about Wiskott-Aldrich syndrome is false?

Autosomal Recessive disorder. ***Autosomal Recessive disorder*** - **Wiskott-Aldrich Syndrome (WAS)** is an **X-linked recessive disorder**, not autosomal recessive. This statement is therefore false, making it the correct answer to the question. - It is caused by mutations in the WAS gene, which encodes the Wiskott-Aldrich syndrome protein (WASp) and is located on the X chromosome. *Eczematous Rash* - Patients with Wiskott-Aldrich syndrome frequently present with severe and persistent **eczematous rash**, which is a key component of the clinical triad. - This rash is often recalcitrant to standard treatments and can be widespread. *Impaired platelet aggregation in response to agonist* - Patients with WAS exhibit **abnormal platelet function**, specifically **impaired aggregation** in response to various agonists. - This functional defect contributes to the bleeding diathesis seen in the syndrome, alongside reduced platelet count. *Thrombocytopenia* - **Thrombocytopenia**, characterized by a low platelet count, is a hallmark feature of Wiskott-Aldrich syndrome. - The platelets are also typically very small in size (**microthrombocytopenia**), which is a distinctive finding.

Q: The most common leukocytoclastic vasculitis affecting children is

Henoch-Schönlein purpura. ***Henoch-Schönlein purpura (HSP/IgA vasculitis)*** - This is the **most common systemic vasculitis in children**, primarily affecting small vessels, and is a classic example of **leukocytoclastic vasculitis**. - Characterized by the classic presentation of **palpable purpura** (non-thrombocytopenic), *arthralgia/arthritis*, *abdominal pain*, and *renal involvement* (hematuria/proteinuria). - IgA deposition in vessel walls is the hallmark pathological finding. *Takayasu arteritis* - This is a *large-vessel vasculitis* predominantly affecting the **aorta and its major branches**, leading to stenoses, occlusions, and aneurysms. - It primarily affects *young women* and is not characterized by leukocytoclastic vasculitis. *Kawasaki disease* - This is a *medium-vessel vasculitis* that primarily affects *infants and young children*, with a risk of **coronary artery aneurysms**. - While it causes vasculitis, it is not typically classified as a leukocytoclastic vasculitis and has distinct clinical features like fever, conjunctivitis, and rash. *Polyarteritis nodosa* - This is a *medium-sized vessel necrotizing vasculitis* that can affect multiple organ systems, but it is *rare in children* and more common in adults. - It is not considered the most common leukocytoclastic vasculitis in children and presents with different clinical manifestations, often involving the *kidneys*, *gut*, and *nerves*.

Question 1

Polyarticular onset JRA involves more than how many joints?

Accepted Answer

4

Answer

5

Answer

3

Answer

6

Question 2

Most supportive laboratory investigation for Henoch-Schönlein purpura is -

Accepted Answer

Serum IgA levels

Answer

C-reactive protein (CRP) levels

Answer

DTPA scan

Answer

Renal biopsy

Question 3

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

Question 4

Most common cause of death in SLE in children

Accepted Answer

Anemia and infections

Answer

Libman sacks endocarditis

Answer

Lupus cerebritis

Answer

Lupus nephritis

Question 5

In which of the following immunodeficiencies is this chest X-ray finding usually seen?

Accepted Answer

Hyper IgE syndrome

Answer

Wiskott-Aldrich syndrome

Answer

Di George syndrome

Answer

Chediak Higashi syndrome

Question 6

Which of the following is a characteristic symptom of Henoch-Schönlein Purpura?

Accepted Answer

Gastrointestinal bleeding

Answer

Purpuric rash on buttocks and legs

Answer

Low platelet count

Answer

Bleeding in the brain

Question 7

All are features of Wiskott-Aldrich syndrome, except which of the following?

Accepted Answer

Decreased IgA level

Answer

Elevated IgE level

Answer

Decreased ratio of CD4 and CD8 cells

Answer

Decreased IgM level

Question 8

Which of the following statements about Wiskott-Aldrich syndrome is false?

Accepted Answer

Autosomal Recessive disorder

Answer

Impaired platelet aggregation in response to agonist

Answer

Thrombocytopenia

Answer

Eczematous Rash

Question 9

A 12-month-old infant with a history of recurrent infections, eczema, generalized edema, and easy bruising is diagnosed with an X-linked, recessive, congenital immunodeficiency, and the complete blood count shows thrombocytopenia. What is the most likely diagnosis?

Accepted Answer

Wiskott-Aldrich syndrome

Answer

Isolated IgA deficiency

Answer

Severe combined immunodeficiency

Answer

DiGeorge syndrome (22q11.2 deletion)

Question 10

The most common leukocytoclastic vasculitis affecting children is

Accepted Answer

Henoch-Schönlein purpura

Answer

Takayasu arteritis

Answer

Kawasaki disease

Answer

Polyarteritis nodosa

Immunology and Allergies — MCQs

Immunology and Allergies — MCQs

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