COMSAE Phase 1 Form 114 Practice Exam 2025–
2026: 100 Questions, Correct Answers & Detailed
Rationales | COMLEX Level 1 Prep
Question 1
A 24-year-old woman presents with fatigue, weight loss, heat intolerance, tremor, and
palpitations. Examination shows a diffuse, nontender goiter and bilateral exophthalmos.
Laboratory studies reveal elevated free T4 and suppressed TSH.
Which mechanism most directly explains her thyroid dysfunction?
A. Antibodies stimulating the TSH receptor
B. Antibodies destroying thyroid peroxidase
C. T-cell destruction of thyroid follicular cells
D. Autonomous secretion of TSH by a pituitary adenoma
Correct Answer: A. Antibodies stimulating the TSH receptor
Rationale: Graves disease results from IgG autoantibodies that bind and stimulate the TSH
receptor, causing increased thyroid hormone synthesis and diffuse thyroid enlargement. The
antibodies also stimulate orbital fibroblasts, contributing to ophthalmopathy. Hashimoto
thyroiditis involves autoimmune destruction and typically causes hypothyroidism.
Question 2
A 19-year-old man develops severe muscle weakness after prolonged fasting. Laboratory studies
demonstrate hypoglycemia, increased ketone production, and elevated serum ammonia. A defect
in fatty-acid oxidation is suspected.
Which pathway is most directly impaired?
A. Glycolysis
B. β-oxidation
C. Pentose phosphate pathway
D. Glycogen synthesis
Correct Answer: B. β-oxidation
,Rationale: Fatty-acid oxidation defects impair the ability to generate energy during fasting.
Because fatty acids cannot be adequately oxidized, patients can develop hypoketotic
hypoglycemia, muscle symptoms, and sometimes hyperammonemia. Medium-chain acyl-CoA
dehydrogenase deficiency is a classic example.
Question 3
A patient develops ptosis, diplopia, and difficulty swallowing that worsen throughout the day
and improve after rest. Which structure is primarily affected?
A. Presynaptic voltage-gated calcium channels
B. Postsynaptic nicotinic acetylcholine receptors
C. Presynaptic voltage-gated sodium channels
D. Muscarinic acetylcholine receptors
Correct Answer: B. Postsynaptic nicotinic acetylcholine receptors
Rationale: Myasthenia gravis is caused by antibodies against postsynaptic acetylcholine
receptors at the neuromuscular junction. Weakness characteristically worsens with repeated
activity. Lambert-Eaton syndrome instead involves antibodies against presynaptic voltage-gated
calcium channels.
Question 4
A patient with severe diarrhea develops metabolic acidosis. Arterial blood gas analysis shows:
pH: 7.25
HCO₃⁻: 14 mEq/L
PCO₂: 29 mm Hg
Which acid-base disorder is present?
A. Respiratory acidosis
B. Respiratory alkalosis
C. Metabolic acidosis with appropriate respiratory compensation
D. Metabolic alkalosis with respiratory compensation
Correct Answer: C. Metabolic acidosis with appropriate respiratory compensation
Rationale: The low bicarbonate indicates metabolic acidosis. The decreased PCO₂ represents
compensatory hyperventilation. Diarrhea causes loss of bicarbonate-rich intestinal fluid,
producing a normal-anion-gap metabolic acidosis.
,Question 5
A 67-year-old man with hypertension develops sudden right-sided weakness and expressive
aphasia. Imaging demonstrates an infarct involving the left cerebral hemisphere.
Which artery is most likely occluded?
A. Right middle cerebral artery
B. Left middle cerebral artery
C. Left posterior cerebral artery
D. Right anterior cerebral artery
Correct Answer: B. Left middle cerebral artery
Rationale: The dominant hemisphere is usually the left hemisphere. The middle cerebral artery
supplies the lateral cerebral cortex, including regions responsible for face/upper-extremity motor
function and language. Dominant MCA infarction can therefore cause contralateral weakness
and aphasia.
Question 6
A 45-year-old woman develops fever, hypotension, diffuse erythema, and multiorgan
dysfunction several hours after placement of a retained tampon. Which bacterial product is
responsible?
A. Exotoxin A
B. Toxic shock syndrome toxin-1
C. Shiga toxin
D. Botulinum toxin
Correct Answer: B. Toxic shock syndrome toxin-1
Rationale: Staphylococcus aureus can produce TSST-1, a superantigen that cross-links MHC II
molecules with T-cell receptors, causing massive cytokine release. The result is fever, rash,
hypotension, and potentially multiorgan failure.
Question 7
A 32-year-old patient presents with acute unilateral low-back pain radiating down the posterior
thigh and calf. Examination reveals decreased Achilles reflex and weakness with plantar flexion.
, Which nerve root is most likely affected?
A. L3
B. L4
C. L5
D. S1
Correct Answer: D. S1
Rationale: An S1 radiculopathy commonly causes pain radiating down the posterior leg,
decreased Achilles reflex, and weakness of plantar flexion. L5 radiculopathy more commonly
affects dorsiflexion and great-toe extension.
Question 8
A patient with chronic hypertension is started on a medication that decreases angiotensin II
formation.
Which additional effect is expected?
A. Increased aldosterone secretion
B. Increased efferent arteriolar constriction
C. Decreased bradykinin concentration
D. Decreased sodium reabsorption
Correct Answer: D. Decreased sodium reabsorption
Rationale: ACE inhibitors decrease formation of angiotensin II, reducing aldosterone secretion
and therefore decreasing sodium and water reabsorption. ACE inhibition also increases
bradykinin, which can cause cough and angioedema.
Question 9
A 7-year-old child has recurrent sinopulmonary infections. Laboratory testing demonstrates
markedly decreased immunoglobulin levels. B-cell maturation is impaired because of a defect in
Bruton's tyrosine kinase.
Which condition is most likely?
A. DiGeorge syndrome
B. X-linked agammaglobulinemia
2026: 100 Questions, Correct Answers & Detailed
Rationales | COMLEX Level 1 Prep
Question 1
A 24-year-old woman presents with fatigue, weight loss, heat intolerance, tremor, and
palpitations. Examination shows a diffuse, nontender goiter and bilateral exophthalmos.
Laboratory studies reveal elevated free T4 and suppressed TSH.
Which mechanism most directly explains her thyroid dysfunction?
A. Antibodies stimulating the TSH receptor
B. Antibodies destroying thyroid peroxidase
C. T-cell destruction of thyroid follicular cells
D. Autonomous secretion of TSH by a pituitary adenoma
Correct Answer: A. Antibodies stimulating the TSH receptor
Rationale: Graves disease results from IgG autoantibodies that bind and stimulate the TSH
receptor, causing increased thyroid hormone synthesis and diffuse thyroid enlargement. The
antibodies also stimulate orbital fibroblasts, contributing to ophthalmopathy. Hashimoto
thyroiditis involves autoimmune destruction and typically causes hypothyroidism.
Question 2
A 19-year-old man develops severe muscle weakness after prolonged fasting. Laboratory studies
demonstrate hypoglycemia, increased ketone production, and elevated serum ammonia. A defect
in fatty-acid oxidation is suspected.
Which pathway is most directly impaired?
A. Glycolysis
B. β-oxidation
C. Pentose phosphate pathway
D. Glycogen synthesis
Correct Answer: B. β-oxidation
,Rationale: Fatty-acid oxidation defects impair the ability to generate energy during fasting.
Because fatty acids cannot be adequately oxidized, patients can develop hypoketotic
hypoglycemia, muscle symptoms, and sometimes hyperammonemia. Medium-chain acyl-CoA
dehydrogenase deficiency is a classic example.
Question 3
A patient develops ptosis, diplopia, and difficulty swallowing that worsen throughout the day
and improve after rest. Which structure is primarily affected?
A. Presynaptic voltage-gated calcium channels
B. Postsynaptic nicotinic acetylcholine receptors
C. Presynaptic voltage-gated sodium channels
D. Muscarinic acetylcholine receptors
Correct Answer: B. Postsynaptic nicotinic acetylcholine receptors
Rationale: Myasthenia gravis is caused by antibodies against postsynaptic acetylcholine
receptors at the neuromuscular junction. Weakness characteristically worsens with repeated
activity. Lambert-Eaton syndrome instead involves antibodies against presynaptic voltage-gated
calcium channels.
Question 4
A patient with severe diarrhea develops metabolic acidosis. Arterial blood gas analysis shows:
pH: 7.25
HCO₃⁻: 14 mEq/L
PCO₂: 29 mm Hg
Which acid-base disorder is present?
A. Respiratory acidosis
B. Respiratory alkalosis
C. Metabolic acidosis with appropriate respiratory compensation
D. Metabolic alkalosis with respiratory compensation
Correct Answer: C. Metabolic acidosis with appropriate respiratory compensation
Rationale: The low bicarbonate indicates metabolic acidosis. The decreased PCO₂ represents
compensatory hyperventilation. Diarrhea causes loss of bicarbonate-rich intestinal fluid,
producing a normal-anion-gap metabolic acidosis.
,Question 5
A 67-year-old man with hypertension develops sudden right-sided weakness and expressive
aphasia. Imaging demonstrates an infarct involving the left cerebral hemisphere.
Which artery is most likely occluded?
A. Right middle cerebral artery
B. Left middle cerebral artery
C. Left posterior cerebral artery
D. Right anterior cerebral artery
Correct Answer: B. Left middle cerebral artery
Rationale: The dominant hemisphere is usually the left hemisphere. The middle cerebral artery
supplies the lateral cerebral cortex, including regions responsible for face/upper-extremity motor
function and language. Dominant MCA infarction can therefore cause contralateral weakness
and aphasia.
Question 6
A 45-year-old woman develops fever, hypotension, diffuse erythema, and multiorgan
dysfunction several hours after placement of a retained tampon. Which bacterial product is
responsible?
A. Exotoxin A
B. Toxic shock syndrome toxin-1
C. Shiga toxin
D. Botulinum toxin
Correct Answer: B. Toxic shock syndrome toxin-1
Rationale: Staphylococcus aureus can produce TSST-1, a superantigen that cross-links MHC II
molecules with T-cell receptors, causing massive cytokine release. The result is fever, rash,
hypotension, and potentially multiorgan failure.
Question 7
A 32-year-old patient presents with acute unilateral low-back pain radiating down the posterior
thigh and calf. Examination reveals decreased Achilles reflex and weakness with plantar flexion.
, Which nerve root is most likely affected?
A. L3
B. L4
C. L5
D. S1
Correct Answer: D. S1
Rationale: An S1 radiculopathy commonly causes pain radiating down the posterior leg,
decreased Achilles reflex, and weakness of plantar flexion. L5 radiculopathy more commonly
affects dorsiflexion and great-toe extension.
Question 8
A patient with chronic hypertension is started on a medication that decreases angiotensin II
formation.
Which additional effect is expected?
A. Increased aldosterone secretion
B. Increased efferent arteriolar constriction
C. Decreased bradykinin concentration
D. Decreased sodium reabsorption
Correct Answer: D. Decreased sodium reabsorption
Rationale: ACE inhibitors decrease formation of angiotensin II, reducing aldosterone secretion
and therefore decreasing sodium and water reabsorption. ACE inhibition also increases
bradykinin, which can cause cough and angioedema.
Question 9
A 7-year-old child has recurrent sinopulmonary infections. Laboratory testing demonstrates
markedly decreased immunoglobulin levels. B-cell maturation is impaired because of a defect in
Bruton's tyrosine kinase.
Which condition is most likely?
A. DiGeorge syndrome
B. X-linked agammaglobulinemia
