NBME CBSE USMLE Step 1 Exam 2
QUESTIONS AND CORRECT ANSWERS
(VERIFIED ANSWERS) PLUS RATIONALES
2025
1. A 25-year-old man presents with muscle cramps and weakness. Serum studies
reveal hypokalemia and metabolic alkalosis. His blood pressure is elevated.
Urinalysis reveals increased chloride excretion. Which of the following is the most
likely diagnosis?
A. Bartter syndrome
B. Liddle syndrome
C. Gitelman syndrome
D. SIADH
E. Addison disease
**Rationale: Liddle syndrome mimics hyperaldosteronism with hypertension,
hypokalemia, and metabolic alkalosis but with low renin and aldosterone. It’s due
to constitutive activation of ENaC in the collecting tubules.
,2. A 5-year-old child presents with recurrent infections and partial albinism.
Peripheral smear shows large granules in neutrophils. What is the most likely
diagnosis?
A. Chronic granulomatous disease
B. Leukocyte adhesion deficiency
C. Chediak-Higashi syndrome
D. Wiskott-Aldrich syndrome
E. DiGeorge syndrome
**Rationale: Chediak-Higashi syndrome features recurrent infections,
oculocutaneous albinism, and giant granules in neutrophils due to a lysosomal
trafficking defect (LYST mutation).
3. A 45-year-old man has difficulty initiating movements, a shuffling gait, and a
resting tremor. His brain shows degeneration of dopaminergic neurons. Which
area is affected?
A. Caudate nucleus
B. Thalamus
C. Globus pallidus
D. Substantia nigra pars compacta
E. Subthalamic nucleus
**Rationale: Parkinson’s disease involves loss of dopaminergic neurons in the
substantia nigra pars compacta, leading to basal ganglia dysfunction.
,4. A 3-day-old newborn develops vomiting and lethargy. Labs show
hyperammonemia. There are no signs of liver failure. Which enzyme is most likely
deficient?
A. Arginase
B. Argininosuccinate synthetase
C. Ornithine transcarbamylase
D. Carbamoyl phosphate synthetase I
E. N-acetylglutamate synthase
**Rationale: Ornithine transcarbamylase deficiency is the most common urea
cycle disorder. It is X-linked, causes hyperammonemia without liver dysfunction,
and results in elevated orotic acid.
5. A 30-year-old man has a painless ulcer on his penis and a generalized
maculopapular rash on the palms and soles. Which test is most appropriate for
confirmation?
A. HIV RNA PCR
B. Tzanck smear
C. HSV serology
D. FTA-ABS
E. Gram stain
**Rationale: The FTA-ABS (fluorescent treponemal antibody absorption) test
confirms syphilis, especially after a positive screening VDRL or RPR test.
, 6. A 68-year-old man has progressive memory loss and difficulty with activities of
daily living. Histology shows neurofibrillary tangles and senile plaques. What is the
most likely diagnosis?
A. Pick disease
B. Alzheimer disease
C. Lewy body dementia
D. Vascular dementia
E. Creutzfeldt-Jakob disease
**Rationale: Alzheimer disease is characterized by β-amyloid plaques and tau
neurofibrillary tangles. It is the most common cause of dementia in the elderly.
7. A 22-year-old man has recurrent episodes of hematuria after upper respiratory
infections. Biopsy shows IgA deposition in the mesangium. Diagnosis?
A. Goodpasture syndrome
B. Alport syndrome
C. IgA nephropathy
D. Minimal change disease
E. Membranous nephropathy
**Rationale: IgA nephropathy (Berger disease) is the most common cause of
glomerulonephritis worldwide and follows mucosal infections.
QUESTIONS AND CORRECT ANSWERS
(VERIFIED ANSWERS) PLUS RATIONALES
2025
1. A 25-year-old man presents with muscle cramps and weakness. Serum studies
reveal hypokalemia and metabolic alkalosis. His blood pressure is elevated.
Urinalysis reveals increased chloride excretion. Which of the following is the most
likely diagnosis?
A. Bartter syndrome
B. Liddle syndrome
C. Gitelman syndrome
D. SIADH
E. Addison disease
**Rationale: Liddle syndrome mimics hyperaldosteronism with hypertension,
hypokalemia, and metabolic alkalosis but with low renin and aldosterone. It’s due
to constitutive activation of ENaC in the collecting tubules.
,2. A 5-year-old child presents with recurrent infections and partial albinism.
Peripheral smear shows large granules in neutrophils. What is the most likely
diagnosis?
A. Chronic granulomatous disease
B. Leukocyte adhesion deficiency
C. Chediak-Higashi syndrome
D. Wiskott-Aldrich syndrome
E. DiGeorge syndrome
**Rationale: Chediak-Higashi syndrome features recurrent infections,
oculocutaneous albinism, and giant granules in neutrophils due to a lysosomal
trafficking defect (LYST mutation).
3. A 45-year-old man has difficulty initiating movements, a shuffling gait, and a
resting tremor. His brain shows degeneration of dopaminergic neurons. Which
area is affected?
A. Caudate nucleus
B. Thalamus
C. Globus pallidus
D. Substantia nigra pars compacta
E. Subthalamic nucleus
**Rationale: Parkinson’s disease involves loss of dopaminergic neurons in the
substantia nigra pars compacta, leading to basal ganglia dysfunction.
,4. A 3-day-old newborn develops vomiting and lethargy. Labs show
hyperammonemia. There are no signs of liver failure. Which enzyme is most likely
deficient?
A. Arginase
B. Argininosuccinate synthetase
C. Ornithine transcarbamylase
D. Carbamoyl phosphate synthetase I
E. N-acetylglutamate synthase
**Rationale: Ornithine transcarbamylase deficiency is the most common urea
cycle disorder. It is X-linked, causes hyperammonemia without liver dysfunction,
and results in elevated orotic acid.
5. A 30-year-old man has a painless ulcer on his penis and a generalized
maculopapular rash on the palms and soles. Which test is most appropriate for
confirmation?
A. HIV RNA PCR
B. Tzanck smear
C. HSV serology
D. FTA-ABS
E. Gram stain
**Rationale: The FTA-ABS (fluorescent treponemal antibody absorption) test
confirms syphilis, especially after a positive screening VDRL or RPR test.
, 6. A 68-year-old man has progressive memory loss and difficulty with activities of
daily living. Histology shows neurofibrillary tangles and senile plaques. What is the
most likely diagnosis?
A. Pick disease
B. Alzheimer disease
C. Lewy body dementia
D. Vascular dementia
E. Creutzfeldt-Jakob disease
**Rationale: Alzheimer disease is characterized by β-amyloid plaques and tau
neurofibrillary tangles. It is the most common cause of dementia in the elderly.
7. A 22-year-old man has recurrent episodes of hematuria after upper respiratory
infections. Biopsy shows IgA deposition in the mesangium. Diagnosis?
A. Goodpasture syndrome
B. Alport syndrome
C. IgA nephropathy
D. Minimal change disease
E. Membranous nephropathy
**Rationale: IgA nephropathy (Berger disease) is the most common cause of
glomerulonephritis worldwide and follows mucosal infections.
