2026 NBME 27 ACTUAL EXAM WITH
COMPLETE QUESTIONS AND CORRECT
ANSWERS RATED A+
A 24-year-old woman presents with fatigue, muscle weakness, and
episodes of palpitations. Laboratory studies show a serum potassium
concentration of 2.7 mEq/L and metabolic alkalosis. Blood pressure is
168/96 mm Hg. Plasma renin activity is low, and plasma aldosterone
concentration is elevated.
Which of the following best explains this patient's findings?
A) Increased renin secretion from the juxtaglomerular cells
B) Autonomous aldosterone secretion from the adrenal cortex
C) Increased cortisol production causing mineralocorticoid receptor
activation
D) Reduced sodium reabsorption in the collecting duct
E) Decreased activity of epithelial sodium channels
✓✓ Correct Answer: B) Autonomous aldosterone secretion from the
adrenal cortex
Rationale:
Primary hyperaldosteronism causes excessive sodium reabsorption and
potassium and hydrogen ion secretion in the distal nephron. The
resulting volume expansion suppresses renin release, producing low
renin with high aldosterone. Patients commonly develop hypertension,
hypokalemia, and metabolic alkalosis. An adrenal aldosterone-
producing adenoma or bilateral adrenal hyperplasia can cause this
condition. In contrast, secondary hyperaldosteronism produces
Page 1 of 90
,increased renin and aldosterone, as occurs with renal artery stenosis or
significant volume depletion.
Question 2
A 67-year-old man develops sudden difficulty speaking and weakness of
the right side of his body. Examination shows expressive aphasia and
weakness involving the right face and upper extremity more than the
lower extremity. The lesion is most likely located in which vascular
territory?
A) Right posterior cerebral artery
B) Left anterior cerebral artery
C) Left middle cerebral artery
D) Right middle cerebral artery
E) Basilar artery
✓✓ Correct Answer: C) Left middle cerebral artery
Rationale:
The dominant cerebral hemisphere is usually the left hemisphere. The
left middle cerebral artery (MCA) supplies the lateral frontal and
parietal cortex, including Broca area, as well as motor regions
controlling the contralateral face and upper extremity. Therefore, a left
MCA infarction can produce expressive aphasia and right face/arm
weakness. The anterior cerebral artery primarily supplies the medial
frontal and parietal cortex, particularly areas controlling the lower
extremity.
Question 3
A 5-year-old boy has recurrent bacterial infections involving the
respiratory and gastrointestinal tracts. Laboratory studies show
Page 2 of 90
,markedly decreased serum immunoglobulin concentrations. Flow
cytometry demonstrates absence of mature B cells.
Which of the following is the most likely underlying defect?
A) Failure of T-cell receptor rearrangement
B) Defective Bruton tyrosine kinase signaling
C) Defective NADPH oxidase activity
D) Failure of class switching
E) Deficiency of adenosine deaminase
✓✓ Correct Answer: B) Defective Bruton tyrosine kinase signaling
Rationale:
X-linked agammaglobulinemia results from a mutation affecting Bruton
tyrosine kinase (BTK). BTK is required for maturation of B-cell
precursors. Affected patients have very low or absent mature B cells
and markedly decreased immunoglobulins, resulting in recurrent
bacterial and enteroviral infections. The condition generally becomes
apparent after maternal IgG levels decline during infancy. T-cell function
is relatively preserved.
Question 4
A 58-year-old woman with hypertension develops progressive shortness
of breath. Echocardiography shows concentric left ventricular
hypertrophy with preserved ejection fraction. Which of the following
best explains the cardiac adaptation?
A) Increased ventricular compliance
B) Increased ventricular radius with reduced wall thickness
C) Increased wall stress caused by chronic volume overload
Page 3 of 90
, D) Increased wall thickness caused by chronic pressure overload
E) Reduced myocardial oxygen consumption
✓✓ Correct Answer: D) Increased wall thickness caused by chronic
pressure overload
Rationale:
Chronic hypertension produces pressure overload, resulting in
concentric left ventricular hypertrophy. According to the relationship
described by Laplace's law, increased ventricular pressure increases wall
stress. The myocardium compensates by increasing wall thickness,
reducing wall stress. Initially, this adaptation helps maintain cardiac
output, but over time the hypertrophied ventricle becomes stiff and can
produce diastolic dysfunction and heart failure with preserved ejection
fraction.
Question 5
A 19-year-old college student develops fever, headache, neck stiffness,
and photophobia. Cerebrospinal fluid analysis demonstrates increased
opening pressure, neutrophilic pleocytosis, increased protein
concentration, and decreased glucose concentration.
Which organism is most likely responsible in an otherwise healthy
young adult?
A) Cryptococcus neoformans
B) Escherichia coli
C) Listeria monocytogenes
D) Neisseria meningitidis
E) Herpes simplex virus type 2
Page 4 of 90
COMPLETE QUESTIONS AND CORRECT
ANSWERS RATED A+
A 24-year-old woman presents with fatigue, muscle weakness, and
episodes of palpitations. Laboratory studies show a serum potassium
concentration of 2.7 mEq/L and metabolic alkalosis. Blood pressure is
168/96 mm Hg. Plasma renin activity is low, and plasma aldosterone
concentration is elevated.
Which of the following best explains this patient's findings?
A) Increased renin secretion from the juxtaglomerular cells
B) Autonomous aldosterone secretion from the adrenal cortex
C) Increased cortisol production causing mineralocorticoid receptor
activation
D) Reduced sodium reabsorption in the collecting duct
E) Decreased activity of epithelial sodium channels
✓✓ Correct Answer: B) Autonomous aldosterone secretion from the
adrenal cortex
Rationale:
Primary hyperaldosteronism causes excessive sodium reabsorption and
potassium and hydrogen ion secretion in the distal nephron. The
resulting volume expansion suppresses renin release, producing low
renin with high aldosterone. Patients commonly develop hypertension,
hypokalemia, and metabolic alkalosis. An adrenal aldosterone-
producing adenoma or bilateral adrenal hyperplasia can cause this
condition. In contrast, secondary hyperaldosteronism produces
Page 1 of 90
,increased renin and aldosterone, as occurs with renal artery stenosis or
significant volume depletion.
Question 2
A 67-year-old man develops sudden difficulty speaking and weakness of
the right side of his body. Examination shows expressive aphasia and
weakness involving the right face and upper extremity more than the
lower extremity. The lesion is most likely located in which vascular
territory?
A) Right posterior cerebral artery
B) Left anterior cerebral artery
C) Left middle cerebral artery
D) Right middle cerebral artery
E) Basilar artery
✓✓ Correct Answer: C) Left middle cerebral artery
Rationale:
The dominant cerebral hemisphere is usually the left hemisphere. The
left middle cerebral artery (MCA) supplies the lateral frontal and
parietal cortex, including Broca area, as well as motor regions
controlling the contralateral face and upper extremity. Therefore, a left
MCA infarction can produce expressive aphasia and right face/arm
weakness. The anterior cerebral artery primarily supplies the medial
frontal and parietal cortex, particularly areas controlling the lower
extremity.
Question 3
A 5-year-old boy has recurrent bacterial infections involving the
respiratory and gastrointestinal tracts. Laboratory studies show
Page 2 of 90
,markedly decreased serum immunoglobulin concentrations. Flow
cytometry demonstrates absence of mature B cells.
Which of the following is the most likely underlying defect?
A) Failure of T-cell receptor rearrangement
B) Defective Bruton tyrosine kinase signaling
C) Defective NADPH oxidase activity
D) Failure of class switching
E) Deficiency of adenosine deaminase
✓✓ Correct Answer: B) Defective Bruton tyrosine kinase signaling
Rationale:
X-linked agammaglobulinemia results from a mutation affecting Bruton
tyrosine kinase (BTK). BTK is required for maturation of B-cell
precursors. Affected patients have very low or absent mature B cells
and markedly decreased immunoglobulins, resulting in recurrent
bacterial and enteroviral infections. The condition generally becomes
apparent after maternal IgG levels decline during infancy. T-cell function
is relatively preserved.
Question 4
A 58-year-old woman with hypertension develops progressive shortness
of breath. Echocardiography shows concentric left ventricular
hypertrophy with preserved ejection fraction. Which of the following
best explains the cardiac adaptation?
A) Increased ventricular compliance
B) Increased ventricular radius with reduced wall thickness
C) Increased wall stress caused by chronic volume overload
Page 3 of 90
, D) Increased wall thickness caused by chronic pressure overload
E) Reduced myocardial oxygen consumption
✓✓ Correct Answer: D) Increased wall thickness caused by chronic
pressure overload
Rationale:
Chronic hypertension produces pressure overload, resulting in
concentric left ventricular hypertrophy. According to the relationship
described by Laplace's law, increased ventricular pressure increases wall
stress. The myocardium compensates by increasing wall thickness,
reducing wall stress. Initially, this adaptation helps maintain cardiac
output, but over time the hypertrophied ventricle becomes stiff and can
produce diastolic dysfunction and heart failure with preserved ejection
fraction.
Question 5
A 19-year-old college student develops fever, headache, neck stiffness,
and photophobia. Cerebrospinal fluid analysis demonstrates increased
opening pressure, neutrophilic pleocytosis, increased protein
concentration, and decreased glucose concentration.
Which organism is most likely responsible in an otherwise healthy
young adult?
A) Cryptococcus neoformans
B) Escherichia coli
C) Listeria monocytogenes
D) Neisseria meningitidis
E) Herpes simplex virus type 2
Page 4 of 90
