COMSAE Phase 1 Form 115 Practice Exam
Questions And Correct Answers (Verified
Answers) Plus Rationales 2025/2026 Q&A |
Instant Download Pdf
1. A 55-year-old man with a history of alcohol use disorder presents with
nystagmus, confusion, and ataxia. Which vitamin deficiency is most likely?
A. Niacin (B3)
B. Thiamine (B1)
C. Pyridoxine (B6)
D. Cobalamin (B12)
B. Thiamine (B1)
rationale: The triad of nystagmus, confusion, and ataxia in an alcoholic
patient is classic for Wernicke encephalopathy, caused by thiamine
deficiency.
2. A 25-year-old woman presents with acute-onset shortness of breath and
sharp chest pain. She has a history of two previous miscarriages. Labs show
prolonged aPTT that does not correct with mixing study. Which antibody is
most likely present?
A. Anti-dsDNA
B. Anti-Jo-1
C. Lupus anticoagulant
D. Anti-CCP
C. Lupus anticoagulant
rationale: Recurrent miscarriages, thrombosis, and a prolonged aPTT that
does not correct with mixing suggest antiphospholipid syndrome; lupus
anticoagulant is a key antibody.
3. A 7-year-old boy has recurrent sinopulmonary infections and chronic
diarrhea. Laboratory studies show very low IgG, IgA, and IgM with absent
B cells. Which genetic defect is most likely?
A. Bruton tyrosine kinase (Btk) mutation
B. DiGeorge syndrome deletion
C. JAK3 mutation
, D. Adenosine deaminase deficiency
A. Bruton tyrosine kinase (Btk) mutation
rationale: X-linked agammaglobulinemia (Bruton) presents with
panhypogammaglobulinemia and absent B cells due to a defect in Btk.
4. Which of the following best describes the mechanism of action of linezolid?
A. Inhibits 50S ribosomal subunit to block peptide bond formation
B. Inhibits 30S ribosomal subunit to cause misreading of mRNA
C. Binds to 50S subunit to block transpeptidation
D. Binds to 23S rRNA of 50S subunit to inhibit initiation complex formation
D. Binds to 23S rRNA of 50S subunit to inhibit initiation complex
formation
rationale: Linezolid is an oxazolidinone that binds to the 23S portion of the
50S ribosome, preventing formation of the initiation complex.
5. A 72-year-old man with hypertension presents with acute-onset severe
headache, photophobia, and neck stiffness. CT head shows subarachnoid
hemorrhage. Which procedure is most appropriate next?
A. Lumbar puncture
B. CT angiography
C. Magnetic resonance venography
D. Electroencephalography
B. CT angiography
rationale: After confirmation of subarachnoid hemorrhage, CT angiography
is performed to identify a potential aneurysm as the source.
6. A 3-year-old child has failure to thrive, hepatosplenomegaly, and coarse
facial features. A bone marrow smear shows foam cells with periodic acid–
Schiff (PAS)–positive inclusions. Which enzyme deficiency is most likely?
A. Sphingomyelinase
B. Glucocerebrosidase
C. Hexosaminidase A
D. Arylsulfatase A
A. Sphingomyelinase
rationale: Foam cells and hepatosplenomegaly in a young child suggest
Niemann-Pick type A/B, caused by sphingomyelinase deficiency.
7. A drug that inhibits the cystic fibrosis transmembrane conductance regulator
(CFTR) chloride channel would most directly affect which tissue?
, A. Gastric parietal cells
B. Renal proximal tubule
C. Airway epithelium
D. Cardiac myocyte
C. Airway epithelium
rationale: CFTR is critical for chloride secretion in airway epithelium; its
dysfunction leads to thick mucus in cystic fibrosis.
8. A 60-year-old woman with a history of osteoporosis presents with acute-
onset severe back pain after sneezing. X-ray shows a vertebral compression
fracture. Which medication is most strongly associated with atypical femoral
fractures but not vertebral fractures?
A. Alendronate
B. Teriparatide
C. Denosumab
D. Raloxifene
A. Alendronate
rationale: Bisphosphonates (e.g., alendronate) are associated with atypical
femoral shaft fractures after long-term use; they are effective for vertebral
fractures.
9. A 45-year-old man with type 2 diabetes mellitus presents with a painful,
swollen right knee. Aspiration reveals needle-shaped, negatively birefringent
crystals under polarized light. Which finding is most likely in this patient?
A. Hyperuricemia
B. Hypocalcemia
C. Hyperphosphatemia
D. Elevated alkaline phosphatase
A. Hyperuricemia
rationale: Negatively birefringent needle-shaped crystals indicate
monosodium urate (gout); gout is associated with hyperuricemia.
10.A newborn has ambiguous genitalia, hyponatremia, hyperkalemia, and
hypotension. Which enzyme deficiency is most likely?
A. 21β-hydroxylase
B. 11β-hydroxylase
C. 17α-hydroxylase
D. 5α-reductase
, A. 21β-hydroxylase
*rationale: Salt-wasting crisis with ambiguous genitalia in a newborn is
classic for 21β-hydroxylase deficiency, the most common cause of
congenital adrenal hyperplasia.*
11.Which of the following is a characteristic feature of a type II
hypersensitivity reaction?
A. IgE-mediated mast cell degranulation
B. Formation of immune complexes deposited in tissues
C. Antibody-dependent cell-mediated cytotoxicity (ADCC)
D. Delayed activation of T lymphocytes
C. Antibody-dependent cell-mediated cytotoxicity (ADCC)
rationale: Type II hypersensitivity involves IgG/IgM antibodies against cell
surface antigens, leading to complement activation and ADCC (e.g.,
hemolytic anemia).
12.A 32-year-old woman presents with episodic flushing, diarrhea, and
wheezing. A liver ultrasound reveals multiple hypoechoic masses. Urine test
shows elevated 5-hydroxyindoleacetic acid (5-HIAA). Which drug can
prevent carcinoid crisis during surgery?
A. Somatostatin analogs
B. Beta-blockers
C. Antihistamines
D. Methotrexate
A. Somatostatin analogs
rationale: Carcinoid syndrome and tumors secrete serotonin; octreotide
(somatostatin analog) prevents carcinoid crisis by inhibiting hormone
release.
13.A 19-year-old college student develops fever, headache, and a petechial
rash. Blood culture grows gram-negative diplococci. Which virulence factor
is most directly responsible for the petechiae?
A. IgA protease
B. Endotoxin (Lipooligosaccharide)
C. Polysaccharide capsule
D. Pili
B. Endotoxin (Lipooligosaccharide)
Questions And Correct Answers (Verified
Answers) Plus Rationales 2025/2026 Q&A |
Instant Download Pdf
1. A 55-year-old man with a history of alcohol use disorder presents with
nystagmus, confusion, and ataxia. Which vitamin deficiency is most likely?
A. Niacin (B3)
B. Thiamine (B1)
C. Pyridoxine (B6)
D. Cobalamin (B12)
B. Thiamine (B1)
rationale: The triad of nystagmus, confusion, and ataxia in an alcoholic
patient is classic for Wernicke encephalopathy, caused by thiamine
deficiency.
2. A 25-year-old woman presents with acute-onset shortness of breath and
sharp chest pain. She has a history of two previous miscarriages. Labs show
prolonged aPTT that does not correct with mixing study. Which antibody is
most likely present?
A. Anti-dsDNA
B. Anti-Jo-1
C. Lupus anticoagulant
D. Anti-CCP
C. Lupus anticoagulant
rationale: Recurrent miscarriages, thrombosis, and a prolonged aPTT that
does not correct with mixing suggest antiphospholipid syndrome; lupus
anticoagulant is a key antibody.
3. A 7-year-old boy has recurrent sinopulmonary infections and chronic
diarrhea. Laboratory studies show very low IgG, IgA, and IgM with absent
B cells. Which genetic defect is most likely?
A. Bruton tyrosine kinase (Btk) mutation
B. DiGeorge syndrome deletion
C. JAK3 mutation
, D. Adenosine deaminase deficiency
A. Bruton tyrosine kinase (Btk) mutation
rationale: X-linked agammaglobulinemia (Bruton) presents with
panhypogammaglobulinemia and absent B cells due to a defect in Btk.
4. Which of the following best describes the mechanism of action of linezolid?
A. Inhibits 50S ribosomal subunit to block peptide bond formation
B. Inhibits 30S ribosomal subunit to cause misreading of mRNA
C. Binds to 50S subunit to block transpeptidation
D. Binds to 23S rRNA of 50S subunit to inhibit initiation complex formation
D. Binds to 23S rRNA of 50S subunit to inhibit initiation complex
formation
rationale: Linezolid is an oxazolidinone that binds to the 23S portion of the
50S ribosome, preventing formation of the initiation complex.
5. A 72-year-old man with hypertension presents with acute-onset severe
headache, photophobia, and neck stiffness. CT head shows subarachnoid
hemorrhage. Which procedure is most appropriate next?
A. Lumbar puncture
B. CT angiography
C. Magnetic resonance venography
D. Electroencephalography
B. CT angiography
rationale: After confirmation of subarachnoid hemorrhage, CT angiography
is performed to identify a potential aneurysm as the source.
6. A 3-year-old child has failure to thrive, hepatosplenomegaly, and coarse
facial features. A bone marrow smear shows foam cells with periodic acid–
Schiff (PAS)–positive inclusions. Which enzyme deficiency is most likely?
A. Sphingomyelinase
B. Glucocerebrosidase
C. Hexosaminidase A
D. Arylsulfatase A
A. Sphingomyelinase
rationale: Foam cells and hepatosplenomegaly in a young child suggest
Niemann-Pick type A/B, caused by sphingomyelinase deficiency.
7. A drug that inhibits the cystic fibrosis transmembrane conductance regulator
(CFTR) chloride channel would most directly affect which tissue?
, A. Gastric parietal cells
B. Renal proximal tubule
C. Airway epithelium
D. Cardiac myocyte
C. Airway epithelium
rationale: CFTR is critical for chloride secretion in airway epithelium; its
dysfunction leads to thick mucus in cystic fibrosis.
8. A 60-year-old woman with a history of osteoporosis presents with acute-
onset severe back pain after sneezing. X-ray shows a vertebral compression
fracture. Which medication is most strongly associated with atypical femoral
fractures but not vertebral fractures?
A. Alendronate
B. Teriparatide
C. Denosumab
D. Raloxifene
A. Alendronate
rationale: Bisphosphonates (e.g., alendronate) are associated with atypical
femoral shaft fractures after long-term use; they are effective for vertebral
fractures.
9. A 45-year-old man with type 2 diabetes mellitus presents with a painful,
swollen right knee. Aspiration reveals needle-shaped, negatively birefringent
crystals under polarized light. Which finding is most likely in this patient?
A. Hyperuricemia
B. Hypocalcemia
C. Hyperphosphatemia
D. Elevated alkaline phosphatase
A. Hyperuricemia
rationale: Negatively birefringent needle-shaped crystals indicate
monosodium urate (gout); gout is associated with hyperuricemia.
10.A newborn has ambiguous genitalia, hyponatremia, hyperkalemia, and
hypotension. Which enzyme deficiency is most likely?
A. 21β-hydroxylase
B. 11β-hydroxylase
C. 17α-hydroxylase
D. 5α-reductase
, A. 21β-hydroxylase
*rationale: Salt-wasting crisis with ambiguous genitalia in a newborn is
classic for 21β-hydroxylase deficiency, the most common cause of
congenital adrenal hyperplasia.*
11.Which of the following is a characteristic feature of a type II
hypersensitivity reaction?
A. IgE-mediated mast cell degranulation
B. Formation of immune complexes deposited in tissues
C. Antibody-dependent cell-mediated cytotoxicity (ADCC)
D. Delayed activation of T lymphocytes
C. Antibody-dependent cell-mediated cytotoxicity (ADCC)
rationale: Type II hypersensitivity involves IgG/IgM antibodies against cell
surface antigens, leading to complement activation and ADCC (e.g.,
hemolytic anemia).
12.A 32-year-old woman presents with episodic flushing, diarrhea, and
wheezing. A liver ultrasound reveals multiple hypoechoic masses. Urine test
shows elevated 5-hydroxyindoleacetic acid (5-HIAA). Which drug can
prevent carcinoid crisis during surgery?
A. Somatostatin analogs
B. Beta-blockers
C. Antihistamines
D. Methotrexate
A. Somatostatin analogs
rationale: Carcinoid syndrome and tumors secrete serotonin; octreotide
(somatostatin analog) prevents carcinoid crisis by inhibiting hormone
release.
13.A 19-year-old college student develops fever, headache, and a petechial
rash. Blood culture grows gram-negative diplococci. Which virulence factor
is most directly responsible for the petechiae?
A. IgA protease
B. Endotoxin (Lipooligosaccharide)
C. Polysaccharide capsule
D. Pili
B. Endotoxin (Lipooligosaccharide)
