NEET-PG 2025 - Pediatrics PYQs Practice Questions

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]

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?

Accepted Answer

Oral calcium + Vitamin D

Answer

Growth hormone therapy

Answer

Phosphate binder

Answer

Calcium supplementation

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?

Accepted Answer

Severe Combined Immunodeficiency (SCID)

Answer

Hypogammaglobulinemia

Answer

Wiskott-Aldrich Syndrome

Answer

DiGeorge Syndrome

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?

Accepted Answer

Nevirapine + Zidovudine for 6 weeks

Answer

Zidovudine for 4 weeks

Answer

Nevirapine for 6 weeks

Answer

Nevirapine for 12 weeks

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?

Accepted Answer

Diazepam

Answer

Valproate

Answer

Doxycycline / Amoxicillin

Answer

Fosphenytoin

NEET-PG 2025 — Pediatrics