KAPLAN USMLE STEP 1 DIAGNOSTIC EXAM
QUESTIONS AND 100% VERIFIED ANSWERS
WITH RATIONALES GRADED A+
GUARANTEED PASS ON THE FIRST ATTEMPT
1.
A 45-year-old man presents with sudden-onset severe chest pain radiating to the
back. Blood pressure is 180/110 mmHg in the right arm and 160/100 mmHg in the
left arm. CT angiography shows a widening of the ascending aorta with an intimal
flap.
Which of the following is the most likely underlying pathology?
A. Atherosclerosis
B. Cystic medial degeneration
C. Hypertrophic cardiomyopathy
D. Giant cell arteritis
E. Takayasu arteritis
Answer: B. Cystic medial degeneration
Rationale:
Acute aortic dissection, especially of the ascending aorta (Stanford type A), is most
commonly associated with cystic medial degeneration, often seen in chronic
hypertension and connective tissue disorders. Atherosclerosis is more associated
with type B dissections or aneurysms. Giant cell arteritis and Takayasu arteritis
involve inflammation of medium/large arteries but are less acutely associated with
dissection.
,2.
A 3-year-old boy presents with developmental delay, coarse facial features, and
hepatosplenomegaly. Laboratory testing reveals elevated lysosomal enzymes in
urine.
Which type of biochemical defect is most likely responsible?
A. Glycogen storage
B. Lysosomal enzyme deficiency
C. Mitochondrial respiratory chain defect
D. Peroxisomal enzyme defect
E. Urea cycle defect
Answer: B. Lysosomal enzyme deficiency
Rationale:
The presentation is consistent with a mucopolysaccharidosis (e.g., Hurler
syndrome). These are lysosomal storage diseases caused by deficient lysosomal
enzymes, leading to accumulation of glycosaminoglycans, coarse facial features,
organomegaly, and developmental delay.
3.
A 28-year-old woman develops sudden shortness of breath and pleuritic chest pain
2 days after a long flight. She has mild tachycardia and hypoxemia. D-dimer is
elevated.
Which of the following is the first-line imaging study to confirm diagnosis?
A. Chest X-ray
B. Ventilation-perfusion scan
C. CT pulmonary angiography
D. MRI of the chest
E. Echocardiography
Answer: C. CT pulmonary angiography
,Rationale:
CT pulmonary angiography is the gold standard for diagnosing pulmonary
embolism due to its high sensitivity and specificity. V/Q scan is used if CT is
contraindicated. Chest X-ray is often normal and cannot rule out PE.
4.
A patient with chronic kidney disease has hyperphosphatemia, hypocalcemia, and
secondary hyperparathyroidism.
Which of the following is the main mechanism of secondary
hyperparathyroidism in CKD?
A. Increased phosphate excretion
B. Decreased calcitriol production
C. Increased calcitonin secretion
D. Primary parathyroid hyperplasia
E. Increased renal calcium reabsorption
Answer: B. Decreased calcitriol production
Rationale:
CKD reduces 1α-hydroxylase activity in the kidneys, decreasing active vitamin D
(calcitriol), leading to hypocalcemia. This stimulates PTH secretion, causing
secondary hyperparathyroidism.
5.
A 60-year-old man develops resting tremor, bradykinesia, and rigidity.
Histopathology shows intraneuronal Lewy bodies composed of alpha-synuclein.
Which brain structure is primarily affected in this disease?
A. Substantia nigra pars compacta
B. Caudate nucleus
C. Globus pallidus
D. Cerebellar cortex
E. Hippocampus
, Answer: A. Substantia nigra pars compacta
Rationale:
Parkinson’s disease is characterized by loss of dopaminergic neurons in the
substantia nigra pars compacta. Lewy bodies (alpha-synuclein aggregates) are
pathognomonic. The resulting dopamine deficiency leads to tremor, rigidity, and
bradykinesia.
6.
A patient presents with jaundice, dark urine, and pruritus. Liver biopsy shows bile
plugs in canaliculi and periportal fibrosis.
Which lab pattern is most consistent with cholestasis?
A. Elevated AST > ALT
B. Elevated ALT > AST
C. Elevated alkaline phosphatase and GGT
D. Elevated CK and LDH
E. Elevated amylase and lipase
Answer: C. Elevated alkaline phosphatase and GGT
Rationale:
Cholestatic liver diseases show a predominant increase in alkaline phosphatase and
GGT. AST and ALT elevations are more indicative of hepatocellular injury.
7.
A newborn fails to pass meconium in the first 48 hours. Contrast enema shows a
transition zone in the distal colon. Rectal biopsy shows absence of ganglion cells.
What is the most likely diagnosis?
A. Hirschsprung disease
B. Meconium ileus
C. Intussusception
D. Volvulus
E. Necrotizing enterocolitis
QUESTIONS AND 100% VERIFIED ANSWERS
WITH RATIONALES GRADED A+
GUARANTEED PASS ON THE FIRST ATTEMPT
1.
A 45-year-old man presents with sudden-onset severe chest pain radiating to the
back. Blood pressure is 180/110 mmHg in the right arm and 160/100 mmHg in the
left arm. CT angiography shows a widening of the ascending aorta with an intimal
flap.
Which of the following is the most likely underlying pathology?
A. Atherosclerosis
B. Cystic medial degeneration
C. Hypertrophic cardiomyopathy
D. Giant cell arteritis
E. Takayasu arteritis
Answer: B. Cystic medial degeneration
Rationale:
Acute aortic dissection, especially of the ascending aorta (Stanford type A), is most
commonly associated with cystic medial degeneration, often seen in chronic
hypertension and connective tissue disorders. Atherosclerosis is more associated
with type B dissections or aneurysms. Giant cell arteritis and Takayasu arteritis
involve inflammation of medium/large arteries but are less acutely associated with
dissection.
,2.
A 3-year-old boy presents with developmental delay, coarse facial features, and
hepatosplenomegaly. Laboratory testing reveals elevated lysosomal enzymes in
urine.
Which type of biochemical defect is most likely responsible?
A. Glycogen storage
B. Lysosomal enzyme deficiency
C. Mitochondrial respiratory chain defect
D. Peroxisomal enzyme defect
E. Urea cycle defect
Answer: B. Lysosomal enzyme deficiency
Rationale:
The presentation is consistent with a mucopolysaccharidosis (e.g., Hurler
syndrome). These are lysosomal storage diseases caused by deficient lysosomal
enzymes, leading to accumulation of glycosaminoglycans, coarse facial features,
organomegaly, and developmental delay.
3.
A 28-year-old woman develops sudden shortness of breath and pleuritic chest pain
2 days after a long flight. She has mild tachycardia and hypoxemia. D-dimer is
elevated.
Which of the following is the first-line imaging study to confirm diagnosis?
A. Chest X-ray
B. Ventilation-perfusion scan
C. CT pulmonary angiography
D. MRI of the chest
E. Echocardiography
Answer: C. CT pulmonary angiography
,Rationale:
CT pulmonary angiography is the gold standard for diagnosing pulmonary
embolism due to its high sensitivity and specificity. V/Q scan is used if CT is
contraindicated. Chest X-ray is often normal and cannot rule out PE.
4.
A patient with chronic kidney disease has hyperphosphatemia, hypocalcemia, and
secondary hyperparathyroidism.
Which of the following is the main mechanism of secondary
hyperparathyroidism in CKD?
A. Increased phosphate excretion
B. Decreased calcitriol production
C. Increased calcitonin secretion
D. Primary parathyroid hyperplasia
E. Increased renal calcium reabsorption
Answer: B. Decreased calcitriol production
Rationale:
CKD reduces 1α-hydroxylase activity in the kidneys, decreasing active vitamin D
(calcitriol), leading to hypocalcemia. This stimulates PTH secretion, causing
secondary hyperparathyroidism.
5.
A 60-year-old man develops resting tremor, bradykinesia, and rigidity.
Histopathology shows intraneuronal Lewy bodies composed of alpha-synuclein.
Which brain structure is primarily affected in this disease?
A. Substantia nigra pars compacta
B. Caudate nucleus
C. Globus pallidus
D. Cerebellar cortex
E. Hippocampus
, Answer: A. Substantia nigra pars compacta
Rationale:
Parkinson’s disease is characterized by loss of dopaminergic neurons in the
substantia nigra pars compacta. Lewy bodies (alpha-synuclein aggregates) are
pathognomonic. The resulting dopamine deficiency leads to tremor, rigidity, and
bradykinesia.
6.
A patient presents with jaundice, dark urine, and pruritus. Liver biopsy shows bile
plugs in canaliculi and periportal fibrosis.
Which lab pattern is most consistent with cholestasis?
A. Elevated AST > ALT
B. Elevated ALT > AST
C. Elevated alkaline phosphatase and GGT
D. Elevated CK and LDH
E. Elevated amylase and lipase
Answer: C. Elevated alkaline phosphatase and GGT
Rationale:
Cholestatic liver diseases show a predominant increase in alkaline phosphatase and
GGT. AST and ALT elevations are more indicative of hepatocellular injury.
7.
A newborn fails to pass meconium in the first 48 hours. Contrast enema shows a
transition zone in the distal colon. Rectal biopsy shows absence of ganglion cells.
What is the most likely diagnosis?
A. Hirschsprung disease
B. Meconium ileus
C. Intussusception
D. Volvulus
E. Necrotizing enterocolitis
