COMSAE Phase 1 Form 115–Style Practice Exam
2026
Questions, Answers & Detailed Rationales —
COMLEX-USA Level 1 Preparation
1.
A 24-year-old woman presents with progressive difficulty swallowing. Imaging reveals a mass
compressing the recurrent laryngeal nerve. Which muscle is most likely to be affected by injury
to this nerve?
A. Cricothyroid
B. Posterior cricoarytenoid
C. Stylopharyngeus
D. Tensor veli palatini
E. Palatoglossus
Answer: B. Posterior cricoarytenoid
Rationale: The recurrent laryngeal nerve supplies all intrinsic muscles of the larynx except the
cricothyroid. The posterior cricoarytenoid is the only muscle that abducts the vocal cords.
2.
A newborn has severe respiratory distress immediately after birth. Imaging shows abdominal
organs occupying the left thoracic cavity and displacement of the heart to the right. Which
embryologic defect is most likely responsible?
A. Failure of tracheoesophageal septation
B. Failure of pleuropericardial membrane fusion
C. Failure of pleuroperitoneal membrane closure
D. Failure of neural tube closure
E. Failure of vitelline duct obliteration
Answer: C. Failure of pleuroperitoneal membrane closure
Rationale: A congenital diaphragmatic hernia most commonly occurs posterolaterally through
the Bochdalek foramen due to failure of pleuroperitoneal membrane closure. Herniation of
abdominal contents compresses the developing lungs.
,3.
A 63-year-old man develops sudden weakness of the right lower face and right arm. He also has
difficulty producing speech, but comprehension is intact. Which cerebral artery is most likely
occluded?
A. Right anterior cerebral artery
B. Right middle cerebral artery
C. Left anterior cerebral artery
D. Left middle cerebral artery
E. Left posterior cerebral artery
Answer: D. Left middle cerebral artery
Rationale: The dominant hemisphere is usually the left hemisphere. A left MCA lesion can
cause contralateral face and upper-extremity weakness and expressive aphasia when Broca area
is involved.
4.
A patient with chronic hypertension develops concentric thickening of the left ventricular wall.
Which cellular adaptation is primarily responsible?
A. Hyperplasia
B. Hypertrophy
C. Metaplasia
D. Dysplasia
E. Atrophy
Answer: B. Hypertrophy
Rationale: Cardiac myocytes have limited ability to divide. Chronic pressure overload therefore
causes hypertrophy, characterized by increased cell size and sarcomere production.
5.
A 45-year-old woman has a mass in the superior pole of the kidney. The tumor secretes
excessive erythropoietin. Which renal cell type normally produces most erythropoietin?
,A. Podocytes
B. Juxtaglomerular cells
C. Peritubular interstitial cells
D. Principal cells
E. Mesangial cells
Answer: C. Peritubular interstitial cells
Rationale: Erythropoietin is primarily produced by specialized interstitial fibroblast-like cells in
the renal cortex and outer medulla in response to hypoxia.
6.
A 7-year-old boy develops periorbital edema and proteinuria after a recent upper respiratory
infection. Renal biopsy by light microscopy appears normal. Electron microscopy demonstrates
fusion of podocyte foot processes. What is the most likely diagnosis?
A. Focal segmental glomerulosclerosis
B. Membranous nephropathy
C. Minimal change disease
D. IgA nephropathy
E. Poststreptococcal glomerulonephritis
Answer: C. Minimal change disease
Rationale: Minimal change disease is the most common cause of nephrotic syndrome in
children. Light microscopy is typically normal, while electron microscopy shows diffuse
podocyte foot-process effacement.
7.
A patient develops metabolic acidosis after prolonged diarrhea. Which renal response helps
compensate for the acid-base disturbance?
A. Decreased hydrogen secretion
B. Decreased bicarbonate reabsorption
C. Increased bicarbonate generation
D. Increased urinary bicarbonate excretion
E. Decreased ammonium production
Answer: C. Increased bicarbonate generation
, Rationale: Metabolic acidosis stimulates renal hydrogen ion excretion, ammonium production,
and generation/reabsorption of bicarbonate, helping restore blood pH.
8.
A patient has a mutation affecting phenylalanine hydroxylase. Which substance will accumulate?
A. Tyrosine
B. Phenylalanine
C. Homocysteine
D. Methylmalonic acid
E. Branched-chain amino acids
Answer: B. Phenylalanine
Rationale: Phenylalanine hydroxylase converts phenylalanine to tyrosine using
tetrahydrobiopterin. Deficiency causes phenylketonuria, characterized by accumulation of
phenylalanine and decreased tyrosine.
9.
A patient presents with hemolytic anemia, jaundice, and splenomegaly. Laboratory testing
reveals increased unconjugated bilirubin. Which process normally converts unconjugated
bilirubin into conjugated bilirubin?
A. Oxidation by cytochrome oxidase
B. Conjugation by UDP-glucuronosyltransferase
C. Hydrolysis by pancreatic lipase
D. Reduction by alcohol dehydrogenase
E. Conjugation by sulfotransferase
Answer: B. Conjugation by UDP-glucuronosyltransferase
Rationale: Hepatocytes conjugate bilirubin with glucuronic acid using UDP-
glucuronosyltransferase, producing water-soluble conjugated bilirubin.
10.
A child has recurrent infections, chronic diarrhea, and failure to thrive. Genetic testing reveals a
mutation in the CFTR gene. Which cellular process is directly impaired?
2026
Questions, Answers & Detailed Rationales —
COMLEX-USA Level 1 Preparation
1.
A 24-year-old woman presents with progressive difficulty swallowing. Imaging reveals a mass
compressing the recurrent laryngeal nerve. Which muscle is most likely to be affected by injury
to this nerve?
A. Cricothyroid
B. Posterior cricoarytenoid
C. Stylopharyngeus
D. Tensor veli palatini
E. Palatoglossus
Answer: B. Posterior cricoarytenoid
Rationale: The recurrent laryngeal nerve supplies all intrinsic muscles of the larynx except the
cricothyroid. The posterior cricoarytenoid is the only muscle that abducts the vocal cords.
2.
A newborn has severe respiratory distress immediately after birth. Imaging shows abdominal
organs occupying the left thoracic cavity and displacement of the heart to the right. Which
embryologic defect is most likely responsible?
A. Failure of tracheoesophageal septation
B. Failure of pleuropericardial membrane fusion
C. Failure of pleuroperitoneal membrane closure
D. Failure of neural tube closure
E. Failure of vitelline duct obliteration
Answer: C. Failure of pleuroperitoneal membrane closure
Rationale: A congenital diaphragmatic hernia most commonly occurs posterolaterally through
the Bochdalek foramen due to failure of pleuroperitoneal membrane closure. Herniation of
abdominal contents compresses the developing lungs.
,3.
A 63-year-old man develops sudden weakness of the right lower face and right arm. He also has
difficulty producing speech, but comprehension is intact. Which cerebral artery is most likely
occluded?
A. Right anterior cerebral artery
B. Right middle cerebral artery
C. Left anterior cerebral artery
D. Left middle cerebral artery
E. Left posterior cerebral artery
Answer: D. Left middle cerebral artery
Rationale: The dominant hemisphere is usually the left hemisphere. A left MCA lesion can
cause contralateral face and upper-extremity weakness and expressive aphasia when Broca area
is involved.
4.
A patient with chronic hypertension develops concentric thickening of the left ventricular wall.
Which cellular adaptation is primarily responsible?
A. Hyperplasia
B. Hypertrophy
C. Metaplasia
D. Dysplasia
E. Atrophy
Answer: B. Hypertrophy
Rationale: Cardiac myocytes have limited ability to divide. Chronic pressure overload therefore
causes hypertrophy, characterized by increased cell size and sarcomere production.
5.
A 45-year-old woman has a mass in the superior pole of the kidney. The tumor secretes
excessive erythropoietin. Which renal cell type normally produces most erythropoietin?
,A. Podocytes
B. Juxtaglomerular cells
C. Peritubular interstitial cells
D. Principal cells
E. Mesangial cells
Answer: C. Peritubular interstitial cells
Rationale: Erythropoietin is primarily produced by specialized interstitial fibroblast-like cells in
the renal cortex and outer medulla in response to hypoxia.
6.
A 7-year-old boy develops periorbital edema and proteinuria after a recent upper respiratory
infection. Renal biopsy by light microscopy appears normal. Electron microscopy demonstrates
fusion of podocyte foot processes. What is the most likely diagnosis?
A. Focal segmental glomerulosclerosis
B. Membranous nephropathy
C. Minimal change disease
D. IgA nephropathy
E. Poststreptococcal glomerulonephritis
Answer: C. Minimal change disease
Rationale: Minimal change disease is the most common cause of nephrotic syndrome in
children. Light microscopy is typically normal, while electron microscopy shows diffuse
podocyte foot-process effacement.
7.
A patient develops metabolic acidosis after prolonged diarrhea. Which renal response helps
compensate for the acid-base disturbance?
A. Decreased hydrogen secretion
B. Decreased bicarbonate reabsorption
C. Increased bicarbonate generation
D. Increased urinary bicarbonate excretion
E. Decreased ammonium production
Answer: C. Increased bicarbonate generation
, Rationale: Metabolic acidosis stimulates renal hydrogen ion excretion, ammonium production,
and generation/reabsorption of bicarbonate, helping restore blood pH.
8.
A patient has a mutation affecting phenylalanine hydroxylase. Which substance will accumulate?
A. Tyrosine
B. Phenylalanine
C. Homocysteine
D. Methylmalonic acid
E. Branched-chain amino acids
Answer: B. Phenylalanine
Rationale: Phenylalanine hydroxylase converts phenylalanine to tyrosine using
tetrahydrobiopterin. Deficiency causes phenylketonuria, characterized by accumulation of
phenylalanine and decreased tyrosine.
9.
A patient presents with hemolytic anemia, jaundice, and splenomegaly. Laboratory testing
reveals increased unconjugated bilirubin. Which process normally converts unconjugated
bilirubin into conjugated bilirubin?
A. Oxidation by cytochrome oxidase
B. Conjugation by UDP-glucuronosyltransferase
C. Hydrolysis by pancreatic lipase
D. Reduction by alcohol dehydrogenase
E. Conjugation by sulfotransferase
Answer: B. Conjugation by UDP-glucuronosyltransferase
Rationale: Hepatocytes conjugate bilirubin with glucuronic acid using UDP-
glucuronosyltransferase, producing water-soluble conjugated bilirubin.
10.
A child has recurrent infections, chronic diarrhea, and failure to thrive. Genetic testing reveals a
mutation in the CFTR gene. Which cellular process is directly impaired?
