CBSE-Style Questions with Rationales ACTUAL
2026\2027
Question 1: Biochemistry
A 4-year-old boy presents with intellectual disability and self-mutilating behavior. Lab results show
hyperuricemia. Which enzyme is deficient?
A. Adenosine deaminase
B. HGPRT
C. Phenylalanine hydroxylase
D. Glucose-6-phosphatase
ANSWER: B. HGPRT
Rationale: Lesch-Nyhan syndrome is an X-linked recessive disorder caused by a deficiency of
hypoxanthine-guanine phosphoribosyltransferase (HGPRT), an enzyme in the purine salvage pathway .
Its deficiency leads to excess uric acid production and characteristic neurological symptoms including
self-mutilation, intellectual disability, and dystonia. Adenosine deaminase deficiency causes SCID.
Phenylalanine hydroxylase deficiency causes PKU. Glucose-6-phosphatase deficiency causes von Gierke
disease .
Question 2: Physiology
,During an experiment, a solution of mixed fatty acids is injected into the duodenum of an experimental
animal. The clearance rate of an intravenous glucose load from the circulation is doubled. These findings
are most likely caused by the secretion of which hormone?
A. Gastrin
B. Glucose-dependent insulinotropic peptide
C. Motilin
D. Secretin
ANSWER: B. Glucose-dependent insulinotropic peptide
Rationale: GIP is secreted by K cells in the duodenum and jejunum in response to fatty acids, amino
acids, and intestinal glucose . It stimulates insulin release from the pancreas, promoting peripheral
glucose uptake and reducing serum glucose concentration. This explains the enhanced glucose clearance
observed. Gastrin stimulates gastric acid secretion without affecting glucose. Motilin stimulates
intestinal peristalsis. Secretin promotes bicarbonate-rich pancreatic secretions .
Question 3: Microbiology/Immunology
A 3-year-old boy is brought to the physician because of recurrent bacterial infections, including
pneumonia and otitis media. Laboratory studies show markedly decreased levels of immunoglobulin of
all classes. Flow cytometry reveals a near absence of CD19+ B cells. Which of the following is the most
likely diagnosis?
A. DiGeorge syndrome
B. Wiskott-Aldrich syndrome
C. X-linked agammaglobulinemia
D. Severe combined immunodeficiency (SCID)
ANSWER: C. X-linked agammaglobulinemia
,Rationale: X-linked agammaglobulinemia (Bruton's disease) results from a mutation in the BTK gene,
essential for B-cell maturation . Patients present after 6 months of age (when maternal antibodies wane)
with recurrent pyogenic infections and absent CD19+ B cells. T-cell numbers are normal. DiGeorge
involves T-cell deficiency from thymic aplasia. SCID affects both T and B cells. Wiskott-Aldrich includes
thrombocytopenia and eczema .
Question 4: Pathology
A 62-year-old man with a 40-pack-year smoking history presents with weight loss, hemoptysis, and
hypercalcemia. Chest X-ray shows a right hilar mass. Which substance is most likely secreted by the
tumor?
A. Adrenocorticotropic hormone (ACTH)
B. Antidiuretic hormone (ADH)
C. Parathyroid hormone-related protein (PTHrP)
D. Calcitonin
ANSWER: C. Parathyroid hormone-related protein (PTHrP)
Rationale: Squamous cell carcinoma of the lung is strongly associated with smoking and commonly
causes paraneoplastic hypercalcemia via secretion of PTHrP . PTHrP mimics parathyroid hormone,
increasing bone resorption and renal calcium reabsorption. Small cell carcinoma is more commonly
associated with ADH (SIADH) or ACTH secretion. Medullary thyroid carcinoma produces calcitonin .
Question 5: Neurology
A 60-year-old man with a history of hypertension presents with sudden-onset severe headache, nausea,
and vomiting. Neurologic examination shows no focal deficits. Non-contrast CT of the head shows a
hyperdense focus in the right basal ganglia. Which is the most common underlying vascular pathology?
A. Saccular aneurysm rupture
, B. Charcot-Bouchard microaneurysm rupture
C. Arteriovenous malformation
D. Amyloid angiopathy
ANSWER: B. Charcot-Bouchard microaneurysm rupture
Rationale: Hypertensive hemorrhage most commonly occurs in the basal ganglia, thalamus, pons, and
cerebellum . It is caused by rupture of Charcot-Bouchard microaneurysms, which form due to chronic
hypertension-induced lipohyalinosis of small penetrating arteries. Saccular aneurysm rupture typically
causes subarachnoid hemorrhage. Amyloid angiopathy is more common in lobar hemorrhages in elderly
patients .
Question 6: Renal/Pharmacology
A 68-year-old woman with type 2 diabetes and hypertension poorly controlled on hydrochlorothiazide
presents with BP 150/96 mmHg. Labs show proteinuria. In addition to current therapy, which is the most
appropriate pharmacotherapy?
A. Metoprolol
B. Lisinopril
C. Amlodipine
D. Doxazosin
ANSWER: B. Lisinopril
Rationale: Lisinopril is an ACE inhibitor preferred in patients with diabetes and proteinuria . ACE
inhibitors reduce intraglomerular pressure and slow progression of diabetic nephropathy by decreasing
efferent arteriolar resistance. They also provide cardiovascular protection. Metoprolol is a beta-blocker,
amlodipine is a calcium channel blocker, and doxazosin is an alpha-blocker—none have the specific
renoprotective benefits of ACE inhibitors in this scenario .
2026\2027
Question 1: Biochemistry
A 4-year-old boy presents with intellectual disability and self-mutilating behavior. Lab results show
hyperuricemia. Which enzyme is deficient?
A. Adenosine deaminase
B. HGPRT
C. Phenylalanine hydroxylase
D. Glucose-6-phosphatase
ANSWER: B. HGPRT
Rationale: Lesch-Nyhan syndrome is an X-linked recessive disorder caused by a deficiency of
hypoxanthine-guanine phosphoribosyltransferase (HGPRT), an enzyme in the purine salvage pathway .
Its deficiency leads to excess uric acid production and characteristic neurological symptoms including
self-mutilation, intellectual disability, and dystonia. Adenosine deaminase deficiency causes SCID.
Phenylalanine hydroxylase deficiency causes PKU. Glucose-6-phosphatase deficiency causes von Gierke
disease .
Question 2: Physiology
,During an experiment, a solution of mixed fatty acids is injected into the duodenum of an experimental
animal. The clearance rate of an intravenous glucose load from the circulation is doubled. These findings
are most likely caused by the secretion of which hormone?
A. Gastrin
B. Glucose-dependent insulinotropic peptide
C. Motilin
D. Secretin
ANSWER: B. Glucose-dependent insulinotropic peptide
Rationale: GIP is secreted by K cells in the duodenum and jejunum in response to fatty acids, amino
acids, and intestinal glucose . It stimulates insulin release from the pancreas, promoting peripheral
glucose uptake and reducing serum glucose concentration. This explains the enhanced glucose clearance
observed. Gastrin stimulates gastric acid secretion without affecting glucose. Motilin stimulates
intestinal peristalsis. Secretin promotes bicarbonate-rich pancreatic secretions .
Question 3: Microbiology/Immunology
A 3-year-old boy is brought to the physician because of recurrent bacterial infections, including
pneumonia and otitis media. Laboratory studies show markedly decreased levels of immunoglobulin of
all classes. Flow cytometry reveals a near absence of CD19+ B cells. Which of the following is the most
likely diagnosis?
A. DiGeorge syndrome
B. Wiskott-Aldrich syndrome
C. X-linked agammaglobulinemia
D. Severe combined immunodeficiency (SCID)
ANSWER: C. X-linked agammaglobulinemia
,Rationale: X-linked agammaglobulinemia (Bruton's disease) results from a mutation in the BTK gene,
essential for B-cell maturation . Patients present after 6 months of age (when maternal antibodies wane)
with recurrent pyogenic infections and absent CD19+ B cells. T-cell numbers are normal. DiGeorge
involves T-cell deficiency from thymic aplasia. SCID affects both T and B cells. Wiskott-Aldrich includes
thrombocytopenia and eczema .
Question 4: Pathology
A 62-year-old man with a 40-pack-year smoking history presents with weight loss, hemoptysis, and
hypercalcemia. Chest X-ray shows a right hilar mass. Which substance is most likely secreted by the
tumor?
A. Adrenocorticotropic hormone (ACTH)
B. Antidiuretic hormone (ADH)
C. Parathyroid hormone-related protein (PTHrP)
D. Calcitonin
ANSWER: C. Parathyroid hormone-related protein (PTHrP)
Rationale: Squamous cell carcinoma of the lung is strongly associated with smoking and commonly
causes paraneoplastic hypercalcemia via secretion of PTHrP . PTHrP mimics parathyroid hormone,
increasing bone resorption and renal calcium reabsorption. Small cell carcinoma is more commonly
associated with ADH (SIADH) or ACTH secretion. Medullary thyroid carcinoma produces calcitonin .
Question 5: Neurology
A 60-year-old man with a history of hypertension presents with sudden-onset severe headache, nausea,
and vomiting. Neurologic examination shows no focal deficits. Non-contrast CT of the head shows a
hyperdense focus in the right basal ganglia. Which is the most common underlying vascular pathology?
A. Saccular aneurysm rupture
, B. Charcot-Bouchard microaneurysm rupture
C. Arteriovenous malformation
D. Amyloid angiopathy
ANSWER: B. Charcot-Bouchard microaneurysm rupture
Rationale: Hypertensive hemorrhage most commonly occurs in the basal ganglia, thalamus, pons, and
cerebellum . It is caused by rupture of Charcot-Bouchard microaneurysms, which form due to chronic
hypertension-induced lipohyalinosis of small penetrating arteries. Saccular aneurysm rupture typically
causes subarachnoid hemorrhage. Amyloid angiopathy is more common in lobar hemorrhages in elderly
patients .
Question 6: Renal/Pharmacology
A 68-year-old woman with type 2 diabetes and hypertension poorly controlled on hydrochlorothiazide
presents with BP 150/96 mmHg. Labs show proteinuria. In addition to current therapy, which is the most
appropriate pharmacotherapy?
A. Metoprolol
B. Lisinopril
C. Amlodipine
D. Doxazosin
ANSWER: B. Lisinopril
Rationale: Lisinopril is an ACE inhibitor preferred in patients with diabetes and proteinuria . ACE
inhibitors reduce intraglomerular pressure and slow progression of diabetic nephropathy by decreasing
efferent arteriolar resistance. They also provide cardiovascular protection. Metoprolol is a beta-blocker,
amlodipine is a calcium channel blocker, and doxazosin is an alpha-blocker—none have the specific
renoprotective benefits of ACE inhibitors in this scenario .
