NBME CBSE HIGH-YIELD MEDICAL
EXAMINATION PREP QUESTIONS AND
ANSWERS
1. A 4-year-old boy exhibits self-mutilation, developmental delay, and gouty arthritis.
Laboratory studies show increased levels of uric acid. Which of the following enzymes is most
likely deficient?
A. Adenosine deaminase
B. Xanthine oxidase
C. Hypoxanthine-guanine phosphoribosyltransferase
D. Glucose-6-phosphatase
Answer: C
Conceptual Explanation: Lesch-Nyhan syndrome is caused by a deficiency in HGPRT,
leading to an inability to salvage purines, resulting in excess uric acid and neurological
symptoms.
2. A 65-year-old male with a history of smoking presents with a persistent cough and weight
loss. Imaging reveals a central lung mass. Biopsy shows small blue cells with scant cytoplasm.
What is the most likely diagnosis?
A. Adenocarcinoma
,B. Small cell carcinoma
C. Squamous cell carcinoma
D. Large cell carcinoma
Answer: B
Conceptual Explanation: Small cell carcinoma of the lung is typically central and
characterized by small, round to oval cells with little cytoplasm (oat cell). It is strongly
associated with smoking.
3. A patient is diagnosed with a bacterial infection and prescribed an antibiotic that inhibits
the 30S ribosomal subunit. Which of the following drugs was likely prescribed?
A. Gentamicin
B. Erythromycin
C. Chloramphenicol
D. Clindamycin
Answer: A
Conceptual Explanation: Aminoglycosides like Gentamicin and Tetracyclines bind to the
30S subunit. Macrolides, chloramphenicol, and clindamycin bind to the 50S subunit.
4. A 25-year-old woman presents with butterfly rash and joint pain. Lab tests reveal anti-
dsDNA antibodies. What is the most likely mechanism of the renal damage in this patient?
A. Type III hypersensitivity
, B. Type II hypersensitivity
C. Type I hypersensitivity
D. Type IV hypersensitivity
Answer: A
Conceptual Explanation: Systemic Lupus Erythematosus (SLE) causes damage via
immune complex deposition, which is a Type III hypersensitivity reaction.
5. A patient presents with high fever, neck stiffness, and photophobia. CSF analysis shows low
glucose, high protein, and many neutrophils. What is the most likely causative agent?
A. Cryptococcus neoformans
B. Streptococcus pneumoniae
C. Coxsackievirus
D. Mycobacterium tuberculosis
Answer: B
Conceptual Explanation: Bacterial meningitis (like S. pneumoniae) typically shows low
glucose, high protein, and neutrophilic pleocytosis. Viral shows normal glucose; Fungal/TB
shows lymphocytic pleocytosis.
6. Which of the following diuretics acts by inhibiting the Na-K-2Cl cotransporter in the thick
ascending limb of the loop of Henle?
A. Hydrochlorothiazide
EXAMINATION PREP QUESTIONS AND
ANSWERS
1. A 4-year-old boy exhibits self-mutilation, developmental delay, and gouty arthritis.
Laboratory studies show increased levels of uric acid. Which of the following enzymes is most
likely deficient?
A. Adenosine deaminase
B. Xanthine oxidase
C. Hypoxanthine-guanine phosphoribosyltransferase
D. Glucose-6-phosphatase
Answer: C
Conceptual Explanation: Lesch-Nyhan syndrome is caused by a deficiency in HGPRT,
leading to an inability to salvage purines, resulting in excess uric acid and neurological
symptoms.
2. A 65-year-old male with a history of smoking presents with a persistent cough and weight
loss. Imaging reveals a central lung mass. Biopsy shows small blue cells with scant cytoplasm.
What is the most likely diagnosis?
A. Adenocarcinoma
,B. Small cell carcinoma
C. Squamous cell carcinoma
D. Large cell carcinoma
Answer: B
Conceptual Explanation: Small cell carcinoma of the lung is typically central and
characterized by small, round to oval cells with little cytoplasm (oat cell). It is strongly
associated with smoking.
3. A patient is diagnosed with a bacterial infection and prescribed an antibiotic that inhibits
the 30S ribosomal subunit. Which of the following drugs was likely prescribed?
A. Gentamicin
B. Erythromycin
C. Chloramphenicol
D. Clindamycin
Answer: A
Conceptual Explanation: Aminoglycosides like Gentamicin and Tetracyclines bind to the
30S subunit. Macrolides, chloramphenicol, and clindamycin bind to the 50S subunit.
4. A 25-year-old woman presents with butterfly rash and joint pain. Lab tests reveal anti-
dsDNA antibodies. What is the most likely mechanism of the renal damage in this patient?
A. Type III hypersensitivity
, B. Type II hypersensitivity
C. Type I hypersensitivity
D. Type IV hypersensitivity
Answer: A
Conceptual Explanation: Systemic Lupus Erythematosus (SLE) causes damage via
immune complex deposition, which is a Type III hypersensitivity reaction.
5. A patient presents with high fever, neck stiffness, and photophobia. CSF analysis shows low
glucose, high protein, and many neutrophils. What is the most likely causative agent?
A. Cryptococcus neoformans
B. Streptococcus pneumoniae
C. Coxsackievirus
D. Mycobacterium tuberculosis
Answer: B
Conceptual Explanation: Bacterial meningitis (like S. pneumoniae) typically shows low
glucose, high protein, and neutrophilic pleocytosis. Viral shows normal glucose; Fungal/TB
shows lymphocytic pleocytosis.
6. Which of the following diuretics acts by inhibiting the Na-K-2Cl cotransporter in the thick
ascending limb of the loop of Henle?
A. Hydrochlorothiazide
