Immunology and Allergies Practice Questions

Q: A child presents with recurrent Staphylococcus infections. Laboratory examination shows very low levels of immunoglobulins (G, A, M, E), and a low quantity of B cells. There is a normal reaction to environmental antigens on the skin. What is the most likely diagnosis?

Bruton's agammaglobulinemia. ***Bruton's agammaglobulinemia***- This X-linked disease is caused by a defect in the **Bruton tyrosine kinase (BTK)** gene, which is essential for B-cell maturation.- The deficiency results in a severe block in B-cell development, leading to **near absence of mature B cells** and consequently, extremely **low levels of all immunoglobulin isotypes** (IgG, A, M, E).*DiGeorge syndrome*- Primary feature is **T-cell deficiency** due to failure of the 3rd and 4th pharyngeal pouches, leading to **thymic hypoplasia**; this would typically impair the skin test response. - Although B cell numbers can sometimes be affected, the hallmark is severe T-cell deficiency, and Ig levels are often normal or near-normal, unlike the pan-hypogammaglobulinemia seen here.*Hyper IgM syndrome*- This condition is characterized by a failure in **isotype switching** (often due to defects in **CD40L**), resulting in normal or high levels of **IgM** but very low levels of IgG, IgA, and IgE.- B cells are present in normal counts, distinguishing it from this patient who has very few B cells and very low IgM.*Common variable immunodeficiency*- CVID typically presents later, in adolescence or adulthood, and causes **hypogammaglobulinemia** (low IgG and usually low IgA/IgM).- While B-cell function is impaired, patients usually have **normal B-cell counts**, contrasting with the severe reduction in B cells seen in this child.

Q: A 5-year-old short stature boy presented with fever and weight loss for 6 weeks. He has been admitted previously for 4 episodes of pneumonia in last year. On examination neck lymph nodes were enlarged and reddish macules were noticed on the face and forehead. Lymph node biopsy shows Hodgkin's disease. What is the diagnosis?

Bloom syndrome. ***Bloom syndrome*** - Bloom syndrome is characterized by **short stature**, a characteristic **photosensitive facial rash** (reddish macules on the face and forehead), and an **increased risk of cancer**, including Hodgkin's lymphoma. - Patients also have a predisposition to **recurrent infections** (like pneumonia), immunoglobulin deficiencies, and **short stature**, all of which fit the clinical picture. *Xeroderma Pigmentosum* - This condition involves extreme **photosensitivity** leading to freckling, solar keratoses, and a very high risk of **skin cancers** (basal cell carcinoma, squamous cell carcinoma, melanoma). - While it involves photosensitivity, it does not typically present with the specific facial rash described, recurrent infections, or Hodgkin's disease in the same manner. *Griscelli syndrome* - Characterized by **partial albinism** (silvery-gray hair and hypopigmented skin), immunodeficiency, and neurological abnormalities. - The facial rash and Hodgkin's disease are not typical features, and the albinism is a key distinguishing sign absent here. *Chediak Higashi syndrome* - This is an autosomal recessive disorder characterized by **partial oculocutaneous albinism**, recurrent pyogenic infections due to defective lysosomal trafficking in phagocytes, and progressive neurological impairment. - While recurrent infections occur, the characteristic facial rash and Hodgkin's lymphoma are not specific to this syndrome, and the albinism is a key differentiating feature.

Q: A 7-year-old boy presents with palpable non-blanching rash starting 3 days back from the ankles and involves lower limbs and buttocks. He had viral URTI previously. BP is normal and KFT is normal. What is the diagnosis?

Henoch-Schönlein purpura. **Henoch-Schönlein purpura** - The classic presentation of a **palpable non-blanching rash** on the lower limbs and buttocks in a child, preceded by a **viral URTI**, is highly characteristic of Henoch-Schönlein purpura (HSP). - Normal blood pressure and kidney function tests show an absence of severe renal involvement, which can be a complication of HSP but is not universally present at onset. *Meningococcemia* - While meningococcemia can cause a **petechial or purpuric rash**, it is typically associated with a rapid onset of severe systemic illness, including **fever**, **meningitis symptoms**, and signs of shock, none of which are described. - The rash in meningococcemia tends to be more widespread and rapidly progressive, often involving the trunk and mucous membranes, with patients appearing critically ill. *Hemolytic uremic syndrome* - This syndrome is characterized by the triad of **hemolytic anemia**, **thrombocytopenia**, and **acute kidney injury**, often preceded by a diarrheal illness (especially E. coli O157:H7). - The patient's normal KFT (kidney function tests) and the absence of a history of severe diarrhea or symptoms of anemia makes HUS unlikely. *Cutis marmorata* - Cutis marmorata is a common, transient **mottled, reticulated vascular pattern on the skin** in response to cold temperatures in infants and young children, predominantly a physiologic response. - It is **blanchable** and has a mesh-like appearance rather than a palpable, non-blanching purpuric rash, and is not associated with previous URTI or vasculitis.

Q: A child presents with low grade fever for 5 days, joint pain in large joints and palpable purpuric rash on lower extremities and buttocks. The most probable diagnosis is:

Henoch-Schönlein purpura. ***Henoch-Schönlein purpura*** - This diagnosis is characterized by the classic triad of **palpable purpura**, especially on the lower extremities and buttocks, **arthralgia** (joint pain), and **abdominal pain**, often preceded by an upper respiratory infection with a low-grade fever. - The disease involves **IgA deposition** in small blood vessels, leading to vasculitis, which explains the purpuric rash. *Rheumatic fever* - While it can cause fever and large joint polyarthritis (migratory in nature), it is typically associated with a history of **streptococcal pharyngitis** and can involve the heart (carditis) and central nervous system (Sydenham chorea), which are not mentioned. - The characteristic rash is **erythema marginatum**, not palpable purpura. *Acute ITP* - **Immune thrombocytopenic purpura (ITP)** involves a low platelet count, leading to purpura and petechiae, but these are typically non-palpable. - ITP does not characteristically cause joint pain or systemic signs of vasculitis like Henoch-Schönlein purpura. *Purpura fulminans* - This is a severe, acute, and often rapidly progressive condition characterized by large, confluent areas of **purpura with necrosis** and gangrene, often associated with sepsis or severe infection, and disseminated intravascular coagulation (DIC). - The presentation in the question describes a less severe, more localized, and palpable purpuric rash with joint pain, not widespread necrosis.

Q: A 6-year-old child with abdominal pain and a rash is shown. Comment on the diagnosis?

Henoch-Schonlein purpura. ***Henoch Schonlein purpura*** - This diagnosis is strongly suggested by the child's age (6 years old), presentation of abdominal pain, and the characteristic **palpable purpuric rash**, particularly on the lower extremities, as seen in the image. - **Henoch-Schönlein purpura (HSP)**, now known as IgA vasculitis, is a systemic small-vessel vasculitis predominantly affecting children, characterized by the classic triad of palpable purpura, arthritis/arthralgia, and abdominal pain. *Kawasaki* - **Kawasaki disease** primarily affects children under 5 years of age and presents with persistent fever, conjunctivitis, oral mucosal changes (strawberry tongue), cervical lymphadenopathy, and a polymorphous rash. Abdominal pain is less common as a primary feature. - The rash in Kawasaki disease is typically not purpuric but can be maculopapular or scarlatiniform, and does not show the characteristic distribution seen in the image. *Varicella* - **Varicella (chickenpox)** is characterized by a pruritic vesicular rash that progresses from macules to papules to vesicles and then crusts, usually starting on the trunk and spreading centrifugally. This is distinctly different from the purpuric rash shown. - While it can cause abdominal pain, the skin lesions are the key differentiator, and the image does not depict vesicular lesions. *Meningococcemia* - **Meningococcemia** is a severe bacterial infection often presenting with petechial or purpuric rash, fever, and signs of sepsis. However, the rash in meningococcemia rapidly progresses to large ecchymoses and is often associated with signs of critical illness (e.g., hypotension, altered mental status). - While purpura is present, the widespread, relatively uniform appearance of the rash, combined with abdominal pain in a 6-year-old, points away from the fulminant course typical of meningococcemia towards a vasculitis like HSP.

Q: A child presents with blotchy rash on legs, back and buttocks. All are true about the condition except:

Low platelets. ***Low platelets*** - The rash described, characterized by blotchy purpura on the legs, back, and buttocks in a child, is highly suggestive of **Henoch-Schönlein purpura (HSP)**, now known as **IgA vasculitis**. - A key diagnostic feature of IgA vasculitis (HSP) is that it is a **non-thrombocytopenic purpura**, meaning **platelet counts are typically normal**; therefore, low platelets would be an incorrect statement regarding this condition. *Crops of palpable purpura* - **Palpable purpura** is the hallmark cutaneous manifestation of IgA vasculitis and is seen in nearly all cases, resulting from inflammation and bleeding from small vessels. - The rash typically occurs in successive "crops" on dependent areas like the **legs, buttocks, and elbows**. *Small vessel vasculitis* - IgA vasculitis is a classic example of a **small vessel vasculitis**, characterized by IgA immune complex deposition in the walls of small blood vessels. - This immune complex deposition leads to inflammation and damage of capillaries, venules, and arterioles. *Nephritis* - **Renal involvement**, specifically nephritis, is a significant complication of IgA vasculitis, occurring in a substantial proportion of patients. - It can manifest as **hematuria, proteinuria**, and potentially progress to renal failure, requiring close monitoring.

Q: Which of the following are causes of secondary immunodeficiency in children? I. Diphenylhydantoin II. Severe malnutrition III. Post-varicella state IV. Nephrotic syndrome Select the correct answer using the code given below :

I, II and IV. ***I, II and IV*** - **Diphenylhydantoin (phenytoin)**, an anticonvulsant, causes immunosuppression through multiple mechanisms including IgA deficiency, hypogammaglobulinemia, and impaired T-cell function, making it a well-documented cause of drug-induced secondary immunodeficiency. - **Severe malnutrition** is one of the most common causes of secondary immunodeficiency worldwide, significantly impairing both cellular and humoral immunity by affecting T cells, B cells, and phagocytic function. - **Nephrotic syndrome** causes loss of immunoglobulins (particularly IgG) in the urine due to increased glomerular permeability, directly resulting in hypogammaglobulinemia and increased susceptibility to encapsulated bacterial infections (especially *Streptococcus pneumoniae*). *II, III and IV* - While **severe malnutrition**, **post-varicella state**, and **nephrotic syndrome** are all causes of immunodeficiency, this option incorrectly excludes diphenylhydantoin. - **Diphenylhydantoin** is a well-established cause of secondary immunodeficiency, not a minor or questionable cause. *I, III and IV* - This option incorrectly excludes **severe malnutrition**, which is one of the most important and prevalent causes of secondary immunodeficiency in children globally. - Severe malnutrition affects multiple components of the immune system and is considered a primary cause in pediatric populations. *I, II and III* - While **diphenylhydantoin**, **severe malnutrition**, and **post-varicella state** can all affect immunity, this option incorrectly excludes **nephrotic syndrome**. - The **post-varicella state** causes transient T-cell lymphopenia, but this is typically temporary and self-limited compared to the sustained immunoglobulin loss in nephrotic syndrome. - **Nephrotic syndrome** represents a more consistent and clinically significant cause of secondary immunodeficiency with a clear mechanism (protein loss in urine).

Q: Eight months old child had history of unusual crying and convulsions following previous vaccination after BCG, DPT & OPV ( first dose), and Hepatitis B. Now parents have brought child for next doses of vaccination. Which vaccine is contraindicated in this situation?

DPT. ***DPT*** - A history of **unusual crying** and **convulsions** after a previous DPT (first dose) is a contraindication for further doses of the pertussis component, necessitating the use of **DT (Diphtheria Tetanus)** without the pertussis component. - The **whole-cell pertussis (wP)** vaccine is particularly associated with such neurological adverse events, leading to the recommendation to avoid subsequent doses in such cases. *DT* - **DT (Diphtheria and Tetanus)** is actually the recommended alternative in this scenario, as it removes the pertussis component which is linked to the previous adverse neurological event. - It provides continued protection against diphtheria and tetanus without the risk associated with the **pertussis vaccine component**. *Measles* - **Measles vaccine** is a live attenuated viral vaccine and is not contraindicated by a history of convulsions or unusual crying following DPT. - The adverse reactions described are not typically associated with the measles vaccine and therefore would not prevent its administration. *Hepatitis B* - There is no contraindication for administering the **Hepatitis B vaccine** based on the described history of unusual crying and convulsions post-DPT. - The **Hepatitis B vaccine** is an inactivated vaccine and its adverse effect profile does not include such neurological events attributed to the DPT vaccine.

Q: A 10-year-old boy presents with fever, joint pain, and a lesion over his hand, as seen in the image below. Which of the following is the clinical finding, and what is the likely diagnosis?

Gottron's papules - Juvenile dermatomyositis. ***Gottron's papules - Juvenile dermatomyositis*** - The image clearly displays **Gottron's papules**, which are **erythematous, scaling papules** symmetrically distributed over the **dorsal aspects of the interphalangeal joints** (MCP and PIP joints). - The clinical presentation of a 10-year-old boy with **fever, joint pain**, and these characteristic skin lesions is highly indicative of **juvenile dermatomyositis (JDM)**, an inflammatory myopathy. *Malar rash - Systemic lupus erythematosus* - A **malar rash** is a common finding in **systemic lupus erythematosus (SLE)**, but it typically presents as an **erythematous rash over the cheeks and bridge of the nose**, sparing the nasolabial folds, and does not exhibit the papular, scaly appearance over the knuckles seen in the image. - While SLE can cause fever and joint pain, the specific skin lesion depicted is not consistent with a malar rash. *Heliotrope rash - Dermatomyositis* - A **heliotrope rash** is another classic skin manifestation of **dermatomyositis**, characterized by a **purplish discoloration around the eyelids**, often accompanied by periorbital edema. - This is distinct from the lesions shown on the knuckles, which are diagnostic of Gottron's papules, not a heliotrope rash. *Erythema multiforme - Stevens-Johnson syndrome* - **Erythema multiforme** is characterized by **targetoid lesions** with concentric rings, often appearing acutely in response to infections or medications. - **Stevens-Johnson syndrome (SJS)** is a severe form of erythema multiforme, involving extensive epidermal detachment and mucosal involvement, which does not match the chronic-appearing, papular lesions on the knuckles in the image.

Question 1

Abdominal pain in Henoch-Schonlein purpura is most commonly due to which of the following mechanisms?

Accepted Answer

Mucosal edema and inflammation of the gastrointestinal tract

Answer

Gastrointestinal hemorrhage

Answer

Intussusception or volvulus

Answer

Associated pancreatic inflammation

Question 2

A child presents with recurrent Staphylococcus infections. Laboratory examination shows very low levels of immunoglobulins (G, A, M, E), and a low quantity of B cells. There is a normal reaction to environmental antigens on the skin. What is the most likely diagnosis?

Accepted Answer

Bruton's agammaglobulinemia

Answer

Common variable immunodeficiency

Answer

Hyper IgM syndrome

Answer

DiGeorge syndrome

Question 3

A 5-year-old short stature boy presented with fever and weight loss for 6 weeks. He has been admitted previously for 4 episodes of pneumonia in last year. On examination neck lymph nodes were enlarged and reddish macules were noticed on the face and forehead. Lymph node biopsy shows Hodgkin's disease. What is the diagnosis?

Accepted Answer

Bloom syndrome

Answer

Xeroderma Pigmentosum

Answer

Griscelli syndrome

Answer

Chediak Higashi syndrome

Question 4

A 7-year-old boy presents with palpable non-blanching rash starting 3 days back from the ankles and involves lower limbs and buttocks. He had viral URTI previously. BP is normal and KFT is normal. What is the diagnosis?

Accepted Answer

Henoch-Schönlein purpura

Answer

Meningococcemia

Answer

Hemolytic uremic syndrome

Answer

Cutis marmorata

Question 5

A child presents with low grade fever for 5 days, joint pain in large joints and palpable purpuric rash on lower extremities and buttocks. The most probable diagnosis is:

Accepted Answer

Henoch-Schönlein purpura

Answer

Rheumatic fever

Answer

Acute ITP

Answer

Purpura fulminans

Question 6

A 6-year-old child with abdominal pain and a rash is shown. Comment on the diagnosis?

Accepted Answer

Henoch-Schonlein purpura

Answer

Kawasaki

Answer

Varicella

Answer

Meningococcemia

Question 7

A child presents with blotchy rash on legs, back and buttocks. All are true about the condition except:

Accepted Answer

Low platelets

Answer

Crops of palpable purpura

Answer

Small vessel vasculitis

Answer

Nephritis

Question 8

Which of the following are causes of secondary immunodeficiency in children?
I. Diphenylhydantoin
II. Severe malnutrition
III. Post-varicella state
IV. Nephrotic syndrome

Select the correct answer using the code given below :

Accepted Answer

I, II and IV

Answer

II, III and IV

Answer

I, III and IV

Answer

I, II and III

Question 9

Eight months old child had history of unusual crying and convulsions following previous vaccination after BCG, DPT & OPV ( first dose), and Hepatitis B. Now parents have brought child for next doses of vaccination. Which vaccine is contraindicated in this situation?

Accepted Answer

DPT

Answer

DT

Answer

Measles

Answer

Hepatitis B

Question 10

A 10-year-old boy presents with fever, joint pain, and a lesion over his hand, as seen in the image below. Which of the following is the clinical finding, and what is the likely diagnosis?

Accepted Answer

Gottron's papules - Juvenile dermatomyositis

Answer

Malar rash - Systemic lupus erythematosus

Answer

Heliotrope rash - Dermatomyositis

Answer

Erythema multiforme - Stevens-Johnson syndrome

Immunology and Allergies — MCQs

Immunology and Allergies — MCQs

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