NEET-PG 2025 — Pediatrics

Q: A 6-month-old infant presents with recurrent infections and failure to thrive. Laboratory investigations reveal a deficiency of adenosine deaminase (ADA). Which of the following immunodeficiency disorders is most likely associated?

Severe Combined Immunodeficiency (SCID). ***Severe Combined Immunodeficiency (SCID)*** - **Adenosine deaminase (ADA) deficiency** is a classic autosomal recessive cause of SCID, resulting in accumulation of toxic metabolites like **dATP**. - These toxic metabolites destroy both **T and B lymphocytes**, leading to profound lymphopenia and the severe clinical picture of recurrent infections and **failure to thrive**. *Hypogammaglobulinemia* - This term generally refers to primary **B-cell intrinsic defects** leading to reduced antibody levels (e.g., X-linked agammaglobulinemia or CVID). - While it causes recurrent infections, the underlying genetic defect is specific to B-cell development or function, not **ADA deficiency** affecting both T and B cells profoundly. *DiGeorge Syndrome* - This syndrome is caused by a defect in the 3rd and 4th pharyngeal pouches, often due to **22q11 microdeletion**, resulting in **thymic aplasia** (T-cell deficiency). - Clinical presentation involves the triad of T-cell defect, **cardiac anomalies** (conotruncal defects), and **hypocalcemia** (parathyroid hypoplasia), not ADA deficiency. *Wiskott-Aldrich Syndrome* - This is an X-linked disorder defined by the classic triad of **eczema**, immunodeficiency, and **thrombocytopenia** (small platelets). - The mutation affects the **WASP gene**, leading to defective cytoskeleton function in hematopoietic cells, which is unrelated to ADA enzymatic deficiency. [Practice more Pediatrics PYQs on OnCourse]

Q: An HIV-positive mother with a viral load of 1200 copies/mL delivers a baby. What is the most appropriate antiretroviral prophylaxis for the newborn?

Nevirapine + Zidovudine for 6 weeks. ***Nevirapine + Zidovudine for 6 weeks*** - This combination is the recommended regimen for **high-risk newborns** in resource-limited settings, defined by a maternal viral load (MVL) greater than 1000 copies/mL or if maternal treatment was **suboptimal/absent**. - The dual prophylaxis provides comprehensive coverage to minimize the risk of **mother-to-child transmission (MTCT)**, which is elevated due to the high viral load (1200 copies/mL). *Nevirapine for 6 weeks* - **Nevirapine monotherapy** is reserved for **low-risk newborns** (MVL < 1000 copies/mL) or when the mother received adequate **antiretroviral therapy (ART)**. - Given the MVL of 1200 copies/mL, the risk is high, making dual therapy necessary. *Nevirapine for 12 weeks* - Extended NVP prophylaxis (12 weeks) is sometimes used if the infant is **breastfed and at high risk**, but current standard guidelines for non-breastfed infants with this MVL recommend 6 weeks of dual therapy. - **Duration of 12 weeks** is typically not the initial prophylaxis choice for a non-breastfed infant born to a mother with a high viral load. *Zidovudine for 4 weeks* - **Zidovudine monotherapy** for 4 weeks is considered inadequate given the mother's high viral load of **1200 copies/mL**. - This regimen (4 weeks of ZDV) is primarily reserved for **low-risk newborns** in settings where dual therapy is not feasible, or for term infants born to mothers with **fully suppressed viral loads** who received continuous ART. [Practice more Pediatrics PYQs on OnCourse]

Q: A 3-year-old child is brought to the emergency room with a generalized seizure following a high-grade fever. What is the first-line drug of choice for seizure control in this acute febrile setting?

Diazepam. ***Diazepam*** - **Benzodiazepines** like Diazepam and Lorazepam are the preferred first-line agents for aborting acute seizures, including **febrile seizures**, due to their rapid onset of action. - They potentiate the inhibitory effects of **GABA** (gamma-aminobutyric acid), quickly halting seizure activity. *Valproate* - Valproate is a broad-spectrum **antiepileptic drug (AED)** used for maintenance therapy, not typically the first choice for acute seizure termination in the emergency setting. - While effective, its onset of action is slower compared to rapid-acting benzodiazepines for emergency control. *Fosphenytoin* - Fosphenytoin is a **prodrug** of Phenytoin, typically reserved for status epilepticus or when benzodiazepines fail, as it lacks the rapid action required for immediate seizure control. - Its use is associated with potential side effects like **cardiac rhythm disturbance** and is generally second or third line. *Doxycycline / Amoxicillin* - These are **antibiotics** (Doxycycline is preferred for atypical pneumonia/tick-borne diseases; Amoxicillin for common bacterial infections) and have absolutely **no role** in the acute control of seizures. - This question relates to seizure management, not the empirical treatment of the fever's underlying infection. [Practice more Pediatrics PYQs on OnCourse]

4 Previous Year Questions with Answers & Explanations

Questions

A 5-year-old child with chronic kidney disease (CKD) presents with bow legs. Laboratory investigations reveal: Serum Calcium: 9.1 mg/dL (normal) Serum Phosphate: 6.9 mg/dL (elevated) Alkaline Phosphatase: Elevated 25(OH) Vitamin D: Low What is the most appropriate next step in management?

A 6-month-old infant presents with recurrent infections and failure to thrive. Laboratory investigations reveal a deficiency of adenosine deaminase (ADA). Which of the following immunodeficiency disorders is most likely associated?

An HIV-positive mother with a viral load of 1200 copies/mL delivers a baby. What is the most appropriate antiretroviral prophylaxis for the newborn?

A 3-year-old child is brought to the emergency room with a generalized seizure following a high-grade fever. What is the first-line drug of choice for seizure control in this acute febrile setting?

NEET-PG 2025 - Pediatrics NEET-PG Practice Questions and MCQs

Question 1: A 5-year-old child with chronic kidney disease (CKD) presents with bow legs. Laboratory investigations reveal: Serum Calcium: 9.1 mg/dL (normal) Serum Phosphate: 6.9 mg/dL (elevated) Alkaline Phosphatase: Elevated 25(OH) Vitamin D: Low What is the most appropriate next step in management?

A. Oral calcium + Vitamin D (Correct Answer)
B. Growth hormone therapy
C. Phosphate binder
D. Calcium supplementation

Explanation: ***Oral calcium + Vitamin D*** - This child has **CKD-Mineral and Bone Disorder (CKD-MBD)** with renal osteodystrophy manifesting as bow legs (rickets). - Laboratory findings show **low 25(OH) Vitamin D** and **hyperphosphatemia** - both need to be addressed. - According to **KDIGO 2017 guidelines**, children with CKD and vitamin D deficiency should receive **vitamin D supplementation** (nutritional forms like cholecalciferol or ergocalciferol for 25(OH)D deficiency). - **Calcium supplementation** is added to maintain calcium homeostasis and suppress secondary hyperparathyroidism. - The combination addresses the **underlying rachitic changes** (bow legs) by correcting both calcium and vitamin D deficiency. - Activated vitamin D (calcitriol) may be added later if needed, but nutritional vitamin D replacement is the initial step for documented 25(OH)D deficiency. *Calcium supplementation alone* - While calcium is necessary, it does **not address the documented vitamin D deficiency**, which is a primary driver of the bone disease. - Vitamin D is essential for calcium absorption and bone mineralization - giving calcium alone will not correct the rickets or adequately suppress PTH. - Monotherapy with calcium is insufficient for managing CKD-MBD with documented vitamin D deficiency. *Phosphate binder* - Although phosphate is elevated (6.9 mg/dL), phosphate binders alone do not address the **severe vitamin D deficiency** or calcium homeostasis. - Phosphate control is important but is **part of comprehensive management**, not the sole initial step when vitamin D deficiency and rickets are present. - Current guidelines recommend addressing vitamin D deficiency concurrently with phosphate management. *Growth hormone therapy* - Growth hormone is indicated for **growth failure in CKD** after metabolic bone disease is optimized. - It does not correct the underlying **renal osteodystrophy** or vitamin D deficiency causing the bow legs. - GH therapy is considered only after stabilization of CKD-MBD parameters.

Question 2: A 6-month-old infant presents with recurrent infections and failure to thrive. Laboratory investigations reveal a deficiency of adenosine deaminase (ADA). Which of the following immunodeficiency disorders is most likely associated?

A. Hypogammaglobulinemia
B. Wiskott-Aldrich Syndrome
C. Severe Combined Immunodeficiency (SCID) (Correct Answer)
D. DiGeorge Syndrome

Explanation: ***Severe Combined Immunodeficiency (SCID)*** - **Adenosine deaminase (ADA) deficiency** is a classic autosomal recessive cause of SCID, resulting in accumulation of toxic metabolites like **dATP**. - These toxic metabolites destroy both **T and B lymphocytes**, leading to profound lymphopenia and the severe clinical picture of recurrent infections and **failure to thrive**. *Hypogammaglobulinemia* - This term generally refers to primary **B-cell intrinsic defects** leading to reduced antibody levels (e.g., X-linked agammaglobulinemia or CVID). - While it causes recurrent infections, the underlying genetic defect is specific to B-cell development or function, not **ADA deficiency** affecting both T and B cells profoundly. *DiGeorge Syndrome* - This syndrome is caused by a defect in the 3rd and 4th pharyngeal pouches, often due to **22q11 microdeletion**, resulting in **thymic aplasia** (T-cell deficiency). - Clinical presentation involves the triad of T-cell defect, **cardiac anomalies** (conotruncal defects), and **hypocalcemia** (parathyroid hypoplasia), not ADA deficiency. *Wiskott-Aldrich Syndrome* - This is an X-linked disorder defined by the classic triad of **eczema**, immunodeficiency, and **thrombocytopenia** (small platelets). - The mutation affects the **WASP gene**, leading to defective cytoskeleton function in hematopoietic cells, which is unrelated to ADA enzymatic deficiency.

Question 3: An HIV-positive mother with a viral load of 1200 copies/mL delivers a baby. What is the most appropriate antiretroviral prophylaxis for the newborn?

A. Nevirapine + Zidovudine for 6 weeks (Correct Answer)
B. Zidovudine for 4 weeks
C. Nevirapine for 6 weeks
D. Nevirapine for 12 weeks

Explanation: ***Nevirapine + Zidovudine for 6 weeks*** - This combination is the recommended regimen for **high-risk newborns** in resource-limited settings, defined by a maternal viral load (MVL) greater than 1000 copies/mL or if maternal treatment was **suboptimal/absent**. - The dual prophylaxis provides comprehensive coverage to minimize the risk of **mother-to-child transmission (MTCT)**, which is elevated due to the high viral load (1200 copies/mL). *Nevirapine for 6 weeks* - **Nevirapine monotherapy** is reserved for **low-risk newborns** (MVL < 1000 copies/mL) or when the mother received adequate **antiretroviral therapy (ART)**. - Given the MVL of 1200 copies/mL, the risk is high, making dual therapy necessary. *Nevirapine for 12 weeks* - Extended NVP prophylaxis (12 weeks) is sometimes used if the infant is **breastfed and at high risk**, but current standard guidelines for non-breastfed infants with this MVL recommend 6 weeks of dual therapy. - **Duration of 12 weeks** is typically not the initial prophylaxis choice for a non-breastfed infant born to a mother with a high viral load. *Zidovudine for 4 weeks* - **Zidovudine monotherapy** for 4 weeks is considered inadequate given the mother's high viral load of **1200 copies/mL**. - This regimen (4 weeks of ZDV) is primarily reserved for **low-risk newborns** in settings where dual therapy is not feasible, or for term infants born to mothers with **fully suppressed viral loads** who received continuous ART.

Question 4: A 3-year-old child is brought to the emergency room with a generalized seizure following a high-grade fever. What is the first-line drug of choice for seizure control in this acute febrile setting?

A. Valproate
B. Doxycycline / Amoxicillin
C. Diazepam (Correct Answer)
D. Fosphenytoin

Explanation: ***Diazepam*** - **Benzodiazepines** like Diazepam and Lorazepam are the preferred first-line agents for aborting acute seizures, including **febrile seizures**, due to their rapid onset of action. - They potentiate the inhibitory effects of **GABA** (gamma-aminobutyric acid), quickly halting seizure activity. *Valproate* - Valproate is a broad-spectrum **antiepileptic drug (AED)** used for maintenance therapy, not typically the first choice for acute seizure termination in the emergency setting. - While effective, its onset of action is slower compared to rapid-acting benzodiazepines for emergency control. *Fosphenytoin* - Fosphenytoin is a **prodrug** of Phenytoin, typically reserved for status epilepticus or when benzodiazepines fail, as it lacks the rapid action required for immediate seizure control. - Its use is associated with potential side effects like **cardiac rhythm disturbance** and is generally second or third line. *Doxycycline / Amoxicillin* - These are **antibiotics** (Doxycycline is preferred for atypical pneumonia/tick-borne diseases; Amoxicillin for common bacterial infections) and have absolutely **no role** in the acute control of seizures. - This question relates to seizure management, not the empirical treatment of the fever's underlying infection.