USMLE STEP 1 MEDICAL EXAMINATION PRACTICE
2026–2027 — ORIGINAL QUIZ BANK VOLUME 3 |
LATEST UPDATE 2026/2027 | PRACTICE QUESTIONS
AND ANSWERS | EXAM REVIEW | 100% CORRECT
ANSWERS | VERIFIED SOLUTIONS | ALREADY
GRADED A+
1. A 45-year-old man presents with progressive muscle weakness that worsens
with activity and improves with rest. He has ptosis and diplopia. Which of
the following is the most likely underlying mechanism?
A) Antibodies against presynaptic calcium channels
B) Antibodies against postsynaptic acetylcholine receptors
C) Degeneration of anterior horn cells
D) Demyelination of peripheral nerves
Correct Answer: B
Myasthenia gravis is caused by autoantibodies against postsynaptic acetylcholine
receptors at the neuromuscular junction, leading to fluctuating weakness that
worsens with activity. Lambert-Eaton syndrome involves presynaptic calcium
channel antibodies and improves with activity. ALS is anterior horn degeneration.
Guillain-Barré is demyelinating.
2. A 12-year-old boy has recurrent infections with encapsulated bacteria.
Serum immunoglobulin levels are low, and tonsils are absent. Which of the
following is the most likely diagnosis?
A) DiGeorge syndrome
B) Bruton agammaglobulinemia
C) Chronic granulomatous disease
D) Wiskott-Aldrich syndrome
,Correct Answer: B
Bruton (X-linked) agammaglobulinemia is characterized by absent B cells, low
immunoglobulins, absent tonsils, and recurrent infections with encapsulated
bacteria. DiGeorge has thymic hypoplasia and cardiac defects. CGD is a neutrophil
defect. Wiskott-Aldrich has thrombocytopenia and eczema.
3. A 25-year-old woman has hemoptysis and nephritis. Serum is positive for
anti-glomerular basement membrane antibodies. Which of the following is
the most likely diagnosis?
A) Wegener granulomatosis
B) Goodpasture syndrome
C) Churg-Strauss syndrome
D) IgA nephropathy
Correct Answer: B
Goodpasture syndrome is characterized by anti-glomerular basement membrane
antibodies causing pulmonary hemorrhage and glomerulonephritis. Wegener is
ANCA-positive with granulomas. Churg-Strauss has asthma and eosinophilia. IgA
nephropathy has mesangial IgA deposits.
4. A 30-year-old man is prescribed a medication that inhibits bacterial
dihydrofolate reductase. Which of the following is the most likely
medication?
A) Sulfamethoxazole
B) Trimethoprim
C) Ciprofloxacin
D) Vancomycin
Correct Answer: B
Trimethoprim inhibits bacterial dihydrofolate reductase, preventing folate
synthesis. Sulfamethoxazole inhibits dihydropteroate synthase. Ciprofloxacin
inhibits DNA gyrase. Vancomycin inhibits cell wall synthesis.
5. A 50-year-old woman has recurrent urinary tract infections. Which of the
following is the most common causative organism?
, A) Pseudomonas aeruginosa
B) Escherichia coli
C) Staphylococcus saprophyticus
D) Enterococcus faecalis
Correct Answer: B
E. coli is the most common cause of urinary tract infections, accounting for over
80% of uncomplicated UTIs. Pseudomonas is more common in hospitalized or
catheterized patients. S. saprophyticus is more common in young sexually active
women. Enterococcus is more common in hospitalized patients.
6. A 35-year-old man is diagnosed with a brain tumor that arises from the
arachnoid cells. Which of the following is the most likely diagnosis?
A) Glioblastoma
B) Meningioma
C) Schwannoma
D) Ependymoma
Correct Answer: B
Meningioma arises from arachnoid cells and is the most common benign brain
tumor. Glioblastoma arises from glial cells. Schwannoma arises from Schwann
cells. Ependymoma arises from ependymal cells lining ventricles.
7. A 40-year-old woman is started on levothyroxine for hypothyroidism. Which
of the following is the correct dosing instruction?
A) Take with meals
B) Take on an empty stomach
C) Take at bedtime with milk
D) Take with an antacid
Correct Answer: B
Levothyroxine should be taken on an empty stomach, ideally in the morning, to
maximize absorption. Food, calcium, and antacids decrease absorption. It should
not be taken at bedtime with milk.
, 8. A 20-year-old man is diagnosed with a condition that causes recurrent
episodes of hypoglycemia and is found to have low C-peptide levels. Which
of the following is the most likely diagnosis?
A) Insulinoma
B) Factitious insulin administration
C) Non-insulin-dependent diabetes
D) Glucagonoma
Correct Answer: B
Factitious insulin administration causes hypoglycemia with low C-peptide because
exogenous insulin suppresses endogenous insulin secretion. Insulinoma causes
hypoglycemia with elevated C-peptide. Non-insulin-dependent diabetes causes
hyperglycemia. Glucagonoma causes hyperglycemia.
9. A 55-year-old man is diagnosed with a lung tumor that is associated with
smoking and has a central location. Which of the following is the most likely
tumor?
A) Adenocarcinoma
B) Squamous cell carcinoma
C) Small cell carcinoma
D) Large cell carcinoma
Correct Answer: B
Squamous cell carcinoma of the lung is strongly associated with smoking and
typically central, often arising in the major bronchi. Adenocarcinoma is usually
peripheral and is the most common lung cancer in nonsmokers. Small cell is also
central but has distinct small blue cells. Large cell is peripheral.
10.A 30-year-old woman is diagnosed with an autoimmune disease that causes
destruction of the exocrine glands. Which of the following is the most likely
antibody?
A) Anti-dsDNA
B) Anti-Ro/SSA
C) Anti-Sm
D) Anti-histone
2026–2027 — ORIGINAL QUIZ BANK VOLUME 3 |
LATEST UPDATE 2026/2027 | PRACTICE QUESTIONS
AND ANSWERS | EXAM REVIEW | 100% CORRECT
ANSWERS | VERIFIED SOLUTIONS | ALREADY
GRADED A+
1. A 45-year-old man presents with progressive muscle weakness that worsens
with activity and improves with rest. He has ptosis and diplopia. Which of
the following is the most likely underlying mechanism?
A) Antibodies against presynaptic calcium channels
B) Antibodies against postsynaptic acetylcholine receptors
C) Degeneration of anterior horn cells
D) Demyelination of peripheral nerves
Correct Answer: B
Myasthenia gravis is caused by autoantibodies against postsynaptic acetylcholine
receptors at the neuromuscular junction, leading to fluctuating weakness that
worsens with activity. Lambert-Eaton syndrome involves presynaptic calcium
channel antibodies and improves with activity. ALS is anterior horn degeneration.
Guillain-Barré is demyelinating.
2. A 12-year-old boy has recurrent infections with encapsulated bacteria.
Serum immunoglobulin levels are low, and tonsils are absent. Which of the
following is the most likely diagnosis?
A) DiGeorge syndrome
B) Bruton agammaglobulinemia
C) Chronic granulomatous disease
D) Wiskott-Aldrich syndrome
,Correct Answer: B
Bruton (X-linked) agammaglobulinemia is characterized by absent B cells, low
immunoglobulins, absent tonsils, and recurrent infections with encapsulated
bacteria. DiGeorge has thymic hypoplasia and cardiac defects. CGD is a neutrophil
defect. Wiskott-Aldrich has thrombocytopenia and eczema.
3. A 25-year-old woman has hemoptysis and nephritis. Serum is positive for
anti-glomerular basement membrane antibodies. Which of the following is
the most likely diagnosis?
A) Wegener granulomatosis
B) Goodpasture syndrome
C) Churg-Strauss syndrome
D) IgA nephropathy
Correct Answer: B
Goodpasture syndrome is characterized by anti-glomerular basement membrane
antibodies causing pulmonary hemorrhage and glomerulonephritis. Wegener is
ANCA-positive with granulomas. Churg-Strauss has asthma and eosinophilia. IgA
nephropathy has mesangial IgA deposits.
4. A 30-year-old man is prescribed a medication that inhibits bacterial
dihydrofolate reductase. Which of the following is the most likely
medication?
A) Sulfamethoxazole
B) Trimethoprim
C) Ciprofloxacin
D) Vancomycin
Correct Answer: B
Trimethoprim inhibits bacterial dihydrofolate reductase, preventing folate
synthesis. Sulfamethoxazole inhibits dihydropteroate synthase. Ciprofloxacin
inhibits DNA gyrase. Vancomycin inhibits cell wall synthesis.
5. A 50-year-old woman has recurrent urinary tract infections. Which of the
following is the most common causative organism?
, A) Pseudomonas aeruginosa
B) Escherichia coli
C) Staphylococcus saprophyticus
D) Enterococcus faecalis
Correct Answer: B
E. coli is the most common cause of urinary tract infections, accounting for over
80% of uncomplicated UTIs. Pseudomonas is more common in hospitalized or
catheterized patients. S. saprophyticus is more common in young sexually active
women. Enterococcus is more common in hospitalized patients.
6. A 35-year-old man is diagnosed with a brain tumor that arises from the
arachnoid cells. Which of the following is the most likely diagnosis?
A) Glioblastoma
B) Meningioma
C) Schwannoma
D) Ependymoma
Correct Answer: B
Meningioma arises from arachnoid cells and is the most common benign brain
tumor. Glioblastoma arises from glial cells. Schwannoma arises from Schwann
cells. Ependymoma arises from ependymal cells lining ventricles.
7. A 40-year-old woman is started on levothyroxine for hypothyroidism. Which
of the following is the correct dosing instruction?
A) Take with meals
B) Take on an empty stomach
C) Take at bedtime with milk
D) Take with an antacid
Correct Answer: B
Levothyroxine should be taken on an empty stomach, ideally in the morning, to
maximize absorption. Food, calcium, and antacids decrease absorption. It should
not be taken at bedtime with milk.
, 8. A 20-year-old man is diagnosed with a condition that causes recurrent
episodes of hypoglycemia and is found to have low C-peptide levels. Which
of the following is the most likely diagnosis?
A) Insulinoma
B) Factitious insulin administration
C) Non-insulin-dependent diabetes
D) Glucagonoma
Correct Answer: B
Factitious insulin administration causes hypoglycemia with low C-peptide because
exogenous insulin suppresses endogenous insulin secretion. Insulinoma causes
hypoglycemia with elevated C-peptide. Non-insulin-dependent diabetes causes
hyperglycemia. Glucagonoma causes hyperglycemia.
9. A 55-year-old man is diagnosed with a lung tumor that is associated with
smoking and has a central location. Which of the following is the most likely
tumor?
A) Adenocarcinoma
B) Squamous cell carcinoma
C) Small cell carcinoma
D) Large cell carcinoma
Correct Answer: B
Squamous cell carcinoma of the lung is strongly associated with smoking and
typically central, often arising in the major bronchi. Adenocarcinoma is usually
peripheral and is the most common lung cancer in nonsmokers. Small cell is also
central but has distinct small blue cells. Large cell is peripheral.
10.A 30-year-old woman is diagnosed with an autoimmune disease that causes
destruction of the exocrine glands. Which of the following is the most likely
antibody?
A) Anti-dsDNA
B) Anti-Ro/SSA
C) Anti-Sm
D) Anti-histone
