NBME CBSE AND USMLE STEP 1
COMPREHENSIVE REVIEW QUESTIONS
AND ANSWERS
1. A 45-year-old male with a history of hypertension is prescribed a medication that acts on
the distal convoluted tubule to inhibit the Na+/Cl- cotransporter. Which of the following side
effects is most likely to occur?
A. Hyperkalemia
B. Hypercalcemia
C. Metabolic acidosis
D. Hyponatremia
Answer: B
Conceptual Explanation: Thiazide diuretics inhibit the Na+/Cl- cotransporter in the distal
convoluted tubule. Unlike loop diuretics, they decrease urinary calcium excretion,
potentially leading to hypercalcemia.
2. A 4-year-old boy presents with intellectual disability, a ‘mousy’ body odor, and fair skin.
Which enzyme is most likely deficient in this patient?
A. Phenylalanine hydroxylase
,B. Homogentisate oxidase
C. Tyrosinase
D. Branched-chain alpha-ketoacid dehydrogenase
Answer: A
Conceptual Explanation: These findings are classic for Phenylketonuria (PKU), caused by
a deficiency in phenylalanine hydroxylase, preventing the conversion of phenylalanine to
tyrosine.
3. A 65-year-old male smoker presents with painless hematuria. Imaging reveals a mass in the
upper pole of the right kidney. What is the most common histological type of this
malignancy?
A. Transitional cell carcinoma
B. Clear cell carcinoma
C. Papillary carcinoma
D. Chromophobe carcinoma
Answer: B
Conceptual Explanation: Clear cell carcinoma is the most common subtype of renal cell
carcinoma (RCC), often associated with VHL gene mutations on chromosome 3.
4. Which of the following mechanisms best describes the action of Macrolide antibiotics?
A. Inhibition of the 30S ribosomal subunit
, B. Inhibition of the 50S ribosomal subunit
C. Inhibition of cell wall synthesis
D. Disruption of the bacterial cell membrane
Answer: B
Conceptual Explanation: Macrolides (like Erythromycin or Azithromycin) bind to the 23S
rRNA of the 50S ribosomal subunit, inhibiting translocation during protein synthesis.
5. A patient with hematuria and hemoptysis is found to have linear immunofluorescence on
renal biopsy. Which of the following is the target of the autoantibodies?
A. Type IV collagen
B. Double-stranded DNA
C. IgG Fc fragment
D. Phospholipase A2 receptor
Answer: A
Conceptual Explanation: Goodpasture syndrome involves antibodies against the alpha-3
chain of Type IV collagen in the glomerular and alveolar basement membranes, resulting in
a linear pattern.
COMPREHENSIVE REVIEW QUESTIONS
AND ANSWERS
1. A 45-year-old male with a history of hypertension is prescribed a medication that acts on
the distal convoluted tubule to inhibit the Na+/Cl- cotransporter. Which of the following side
effects is most likely to occur?
A. Hyperkalemia
B. Hypercalcemia
C. Metabolic acidosis
D. Hyponatremia
Answer: B
Conceptual Explanation: Thiazide diuretics inhibit the Na+/Cl- cotransporter in the distal
convoluted tubule. Unlike loop diuretics, they decrease urinary calcium excretion,
potentially leading to hypercalcemia.
2. A 4-year-old boy presents with intellectual disability, a ‘mousy’ body odor, and fair skin.
Which enzyme is most likely deficient in this patient?
A. Phenylalanine hydroxylase
,B. Homogentisate oxidase
C. Tyrosinase
D. Branched-chain alpha-ketoacid dehydrogenase
Answer: A
Conceptual Explanation: These findings are classic for Phenylketonuria (PKU), caused by
a deficiency in phenylalanine hydroxylase, preventing the conversion of phenylalanine to
tyrosine.
3. A 65-year-old male smoker presents with painless hematuria. Imaging reveals a mass in the
upper pole of the right kidney. What is the most common histological type of this
malignancy?
A. Transitional cell carcinoma
B. Clear cell carcinoma
C. Papillary carcinoma
D. Chromophobe carcinoma
Answer: B
Conceptual Explanation: Clear cell carcinoma is the most common subtype of renal cell
carcinoma (RCC), often associated with VHL gene mutations on chromosome 3.
4. Which of the following mechanisms best describes the action of Macrolide antibiotics?
A. Inhibition of the 30S ribosomal subunit
, B. Inhibition of the 50S ribosomal subunit
C. Inhibition of cell wall synthesis
D. Disruption of the bacterial cell membrane
Answer: B
Conceptual Explanation: Macrolides (like Erythromycin or Azithromycin) bind to the 23S
rRNA of the 50S ribosomal subunit, inhibiting translocation during protein synthesis.
5. A patient with hematuria and hemoptysis is found to have linear immunofluorescence on
renal biopsy. Which of the following is the target of the autoantibodies?
A. Type IV collagen
B. Double-stranded DNA
C. IgG Fc fragment
D. Phospholipase A2 receptor
Answer: A
Conceptual Explanation: Goodpasture syndrome involves antibodies against the alpha-3
chain of Type IV collagen in the glomerular and alveolar basement membranes, resulting in
a linear pattern.
