A 24-year-old man presents to the emergency department after a motor vehicle accident. The patient was at a stop when he was rear-ended from behind by a vehicle traveling at 11 miles per hour. The patient complains of severe back pain but states he otherwise feels well. The patient is currently seeing a physical therapist who is giving him exercises to alleviate the back pain that is present every morning, relived by activity, and worse with inactivity. He is a student at the university and is struggling with his grades. His temperature is 98.4°F (36.9°C), blood pressure is 117/78 mmHg, pulse is 116/min, respirations are 12/min, and oxygen saturation is 99% on room air. Physical exam demonstrates a decreased range of motion of the patient's spine and tenderness to palpation over the vertebrae. The rest of the exam is deferred due to pain. The patient is requesting a note to excuse him from final exams and work. Which of the following is the most likely diagnosis in this patient?
Q42
A 45-year-old man with a body mass index of 45 kg/m^2 presents to his primary care doctor with right hip pain. He asserts that the pain is instigated by walking up and down stairs around a construction site which he oversees. On physical exam, his hips are symmetric and equal with no tenderness to palpation bilaterally. His left lower extremity appears grossly normal with full range of motion. His right knee appears symmetric, but the patient whimpers when the anteromedial part of the tibial plateau is pressed. No other parts of his knee are tender. No tenderness is elicited with extension, flexion, varus, and valgus movements of the knee. McMurray's test is negative with both internal and external rotation of the right leg. What is the most likely diagnosis?
Q43
A 2-month-old boy is brought to the emergency room by his mother who reports he has appeared lethargic for the past 3 hours. She reports that she left the patient with a new nanny this morning, and he was behaving normally. When she got home in the afternoon, the patient seemed lethargic and would not breastfeed as usual. At birth, the child had an Apgar score of 8/9 and weighed 2.8 kg (6.1 lb). Growth has been in the 90th percentile, and the patient has been meeting all developmental milestones. There is no significant past medical history, and vaccinations are up-to-date. On physical examination, the patient does not seem arousable. Ophthalmologic examination shows retinal hemorrhages. Which of the following findings would most likely be expected on a noncontrast CT scan of the head?
Q44
A 72-year-old man is brought to the physician by his wife for memory issues over the last 7 months. The patient's wife feels that he has gradually become more forgetful. He commonly misplaces his car keys and forgets his children's names. He seems to have forgotten how to make dinner and sometimes serves uncooked noodles or raw meat. One night he parked his car in a neighbor's bushes and was found wandering the street. He has a history of hypertension, hyperlipidemia, and COPD. Current medications include atorvastatin, metoprolol, ipratropium, and fluticasone. Vital signs are within normal limits. He is alert and oriented to person and place only. Neurologic examination shows no focal findings. His Mini-Mental State Examination score is 19/30. A complete blood count and serum concentrations of electrolytes, urea nitrogen, creatinine, thyroid-stimulating hormone, liver function tests, vitamin B12 (cobalamin), and folate are within the reference range. Which of the following is the most appropriate next step in diagnosis?
Q45
A 27-year-old female presents to her primary care physician with a chief complaint of pain in her lower extremity. The patient states that the pain has gradually worsened over the past month. The patient states that her pain is worsened when she is training. The patient is a business student who does not have a significant past medical history and is currently not on any medications. She admits to having unprotected sex with multiple partners and can not recall her last menses. She drinks 7 to 10 shots of liquor on the weekends and smokes marijuana occasionally. She recently joined the cross country team and has been training for an upcoming meet. Her temperature is 99.5°F (37.5°C), pulse is 88/min, blood pressure is 100/70 mmHg, respirations are 10/min, and oxygen saturation is 97% on room air. On physical exam you note a very pale young woman in no current distress. Pain is localized to the lateral aspect of the knee and is reproduced upon palpation. Physical exam of the knee, hip, and ankle is otherwise within normal limits. The patient has 1+ reflexes and 2+ strength in all extremities. A test for STI's performed one week ago came back negative for infection. Which of the following is the most likely explanation for this patient's presentation?
Q46
A 45-year-old woman comes to the emergency department because of right upper abdominal pain and nausea that have become progressively worse since eating a large meal 8 hours ago. She has had intermittent pain similar to this before, but it has never lasted this long. She has a history of hypertension and type 2 diabetes mellitus. She does not smoke or drink alcohol. Current medications include metformin and enalapril. Her temperature is 38.5°C (101.3°F), pulse is 90/min, and blood pressure is 130/80 mm Hg. The abdomen is soft, and bowel sounds are normal. The patient has sudden inspiratory arrest during right upper quadrant palpation. Laboratory studies show a leukocyte count of 13,000/mm3. Serum alkaline phosphatase, total bilirubin, amylase, and aspartate aminotransferase levels are within the reference ranges. Imaging is most likely to show which of the following findings?
Q47
A 51-year-old homeless man presents to the emergency department with severe abdominal pain and cramping for the past 3 hours. He endorses radiation to his back. He adds that he vomited multiple times. He admits having been hospitalized repeatedly for alcohol intoxication and abdominal pain. His temperature is 103.8° F (39.8° C), respiratory rate is 15/min, pulse is 107/min, and blood pressure is 100/80 mm Hg. He refuses a physical examination due to severe pain. Blood work reveals the following:
Serum:
Albumin: 3.2 gm/dL
Alkaline phosphatase: 150 U/L
Alanine aminotransferase: 76 U/L
Aspartate aminotransferase: 155 U/L
Gamma-glutamyl transpeptidase: 202 U/L
Lipase: 800 U/L
What is the most likely diagnosis of this patient?
Q48
A previously healthy 18-year-old woman comes to the physician because of a 2-day history of swelling and itchiness of her mouth and lips. It decreases when she eats cold foods such as frozen fruit. Four days ago, she underwent orthodontic wire-placement on her upper and lower teeth. Since then, she has been taking ibuprofen twice daily for the pain. For the past 6 months, she has been on a strict vegan diet. She is sexually active with one partner and uses condoms consistently. She had chickenpox that resolved spontaneously when she was 6 years old. Her vitals are within normal limits. Examination shows diffuse erythema and edema of the buccal mucosa with multiple serous vesicles and shallow ulcers. Stroking the skin with pressure does not cause blistering of the skin. The remainder of the examination shows no abnormalities. Which of the following is the most likely cause of these symptoms?
Q49
A 36-year-old woman is brought to the emergency room by her husband for “weird behavior" for the past several weeks. He reports that her right arm has been moving uncontrollably in a writhing movement and that she has been especially irritable. She has a history of depression, which was diagnosed 4 years ago and is currently being treated with sertraline. She denies any recent fever, trauma, infections, travel, weakness, or sensory changes. She was adopted so is unsure of her family history. Which of the following is the most likely explanation for her symptoms?
Q50
Three days after undergoing laparoscopic colectomy, a 67-year-old man reports swelling and pain in his right leg. He was diagnosed with colon cancer 1 month ago. His temperature is 38.5°C (101.3°F). Physical examination shows swelling of the right leg from the ankle to the thigh. There is no erythema or rash. Which of the following is likely to be most helpful in establishing the diagnosis?
Differential diagnosis US Medical PG Practice Questions and MCQs
Question 41: A 24-year-old man presents to the emergency department after a motor vehicle accident. The patient was at a stop when he was rear-ended from behind by a vehicle traveling at 11 miles per hour. The patient complains of severe back pain but states he otherwise feels well. The patient is currently seeing a physical therapist who is giving him exercises to alleviate the back pain that is present every morning, relived by activity, and worse with inactivity. He is a student at the university and is struggling with his grades. His temperature is 98.4°F (36.9°C), blood pressure is 117/78 mmHg, pulse is 116/min, respirations are 12/min, and oxygen saturation is 99% on room air. Physical exam demonstrates a decreased range of motion of the patient's spine and tenderness to palpation over the vertebrae. The rest of the exam is deferred due to pain. The patient is requesting a note to excuse him from final exams and work. Which of the following is the most likely diagnosis in this patient?
A. Spondylolisthesis
B. Malingering
C. Herniated nucleus pulposus
D. Vertebral fracture
E. Musculoskeletal strain (Correct Answer)
Explanation: ***Musculoskeletal strain***
- The patient has a **pre-existing chronic back pain condition** (morning stiffness relieved by activity) that is being managed with physical therapy, suggesting a baseline musculoskeletal issue.
- The **low-speed motor vehicle accident** (11 mph) is unlikely to cause significant structural injury and more likely represents an **acute-on-chronic exacerbation** of his underlying musculoskeletal condition.
- While the chronic pattern (morning stiffness, improved with activity) raises consideration for inflammatory spondyloarthropathy, among the options provided, musculoskeletal strain best captures the **acute exacerbation of chronic mechanical back pain** in the context of minor trauma.
- The patient's request for excuse from exams may represent legitimate need for rest or possible secondary gain, but does not change the primary musculoskeletal diagnosis.
*Spondylolisthesis*
- This involves **anterior slippage of one vertebra over another** and typically presents with mechanical back pain that worsens with **extension and activity** (not relieved by activity as in this patient).
- There is no mention of the characteristic **step-off deformity** on palpation or radicular symptoms that often accompany symptomatic spondylolisthesis.
- The patient's chronic pain pattern of improvement with activity argues against this diagnosis.
*Malingering*
- **Malingering** involves intentional fabrication or gross exaggeration of symptoms for external gain (avoiding exams/work).
- However, this patient has **documented chronic back pain** with ongoing physical therapy, suggesting real underlying pathology rather than pure fabrication.
- While secondary gain may be a factor, the presence of actual pre-existing symptoms and objective findings (decreased ROM, tenderness) makes pure malingering less likely.
*Herniated nucleus pulposus*
- A **herniated disc** typically presents with acute **radicular pain** radiating into the lower extremities, often with neurological deficits (weakness, numbness, reflex changes).
- This patient's presentation is primarily **axial back pain** without mention of leg pain, paresthesias, or neurological deficits, making HNP unlikely.
- The chronic nature and activity-related improvement pattern is atypical for acute disc herniation.
*Vertebral fracture*
- **Vertebral compression fractures** require either significant trauma or underlying bone pathology (osteoporosis, malignancy).
- The **low-speed impact** (11 mph rear-end collision) in a young, otherwise healthy 24-year-old male is insufficient mechanism for vertebral fracture.
- While there is tenderness over vertebrae, the patient's stable vital signs (aside from mild tachycardia likely from pain/anxiety) and absence of neurological compromise make acute fracture very unlikely.
Question 42: A 45-year-old man with a body mass index of 45 kg/m^2 presents to his primary care doctor with right hip pain. He asserts that the pain is instigated by walking up and down stairs around a construction site which he oversees. On physical exam, his hips are symmetric and equal with no tenderness to palpation bilaterally. His left lower extremity appears grossly normal with full range of motion. His right knee appears symmetric, but the patient whimpers when the anteromedial part of the tibial plateau is pressed. No other parts of his knee are tender. No tenderness is elicited with extension, flexion, varus, and valgus movements of the knee. McMurray's test is negative with both internal and external rotation of the right leg. What is the most likely diagnosis?
A. Patellar tendinitis
B. Prepatellar bursitis
C. Medial meniscus tear
D. Pes anserine bursitis (Correct Answer)
E. Lateral meniscus tear
Explanation: **Pes anserine bursitis**
- The patient's presentation with **right hip pain (referred from the knee)**, exacerbated by climbing stairs and tenderness specifically over the **anteromedial tibial plateau**, is highly characteristic of pes anserine bursitis. The patient's **obesity (BMI 45 kg/m^2)** is a significant risk factor.
- The **lack of tenderness** with other knee movements and a **negative McMurray's test** helps rule out meniscal tears. The pain is often described as hip pain due to radiation from the knee.
*Patellar tendinitis*
- This condition typically presents with localized pain and tenderness directly over the **patellar tendon**, just below the patella.
- Pain is usually worsened by activities involving jumping or squatting, and not primarily by pressure on the anteromedial tibial plateau.
*Prepatellar bursitis*
- This involves inflammation of the bursa located directly **over the patella**, often due to direct trauma or prolonged kneeling.
- The hallmark is **swelling and tenderness directly over the patella**, which is not described in this patient.
*Medial meniscus tear*
- While a medial meniscus tear can cause pain on the medial side of the knee, it is often associated with a **positive McMurray's test**, catching, locking, or giving way.
- Tenderness would typically be along the **medial joint line**, and not specifically the more distal anteromedial tibial plateau where the pes anserinus bursa is located.
*Lateral meniscus tear*
- A lateral meniscus tear would cause pain and tenderness predominantly on the **lateral aspect of the knee**.
- Similar to a medial meniscus tear, it is often associated with a **positive McMurray's test**, catching, or locking symptoms, none of which are present here.
Question 43: A 2-month-old boy is brought to the emergency room by his mother who reports he has appeared lethargic for the past 3 hours. She reports that she left the patient with a new nanny this morning, and he was behaving normally. When she got home in the afternoon, the patient seemed lethargic and would not breastfeed as usual. At birth, the child had an Apgar score of 8/9 and weighed 2.8 kg (6.1 lb). Growth has been in the 90th percentile, and the patient has been meeting all developmental milestones. There is no significant past medical history, and vaccinations are up-to-date. On physical examination, the patient does not seem arousable. Ophthalmologic examination shows retinal hemorrhages. Which of the following findings would most likely be expected on a noncontrast CT scan of the head?
A. Lens-shaped hematoma
B. Cortical atrophy
C. Crescent-shaped hematoma (Correct Answer)
D. Blood in the basal cisterns
E. Multiple cortical and subcortical infarcts
Explanation: ***Crescent-shaped hematoma***
- The clinical presentation with **lethargy**, a history of being with a **new caregiver**, and **retinal hemorrhages** strongly suggests **abusive head trauma** (shaken baby syndrome).
- This typically results in a **subdural hematoma**, which appears as a **crescent-shaped collection of blood** on a noncontrast CT scan, reflecting bleeding into the potential space between the dura mater and arachnoid mater.
*Lens-shaped hematoma*
- A **lens-shaped (biconvex) hematoma** on CT is characteristic of an **epidural hematoma**, which typically results from a **skull fracture** tearing a meningeal artery.
- While head trauma is present, the specific findings (retinal hemorrhages, lack of skull fracture mention, and mechanism of shaking) are more consistent with subdural rather than epidural bleeding.
*Cortical atrophy*
- **Cortical atrophy** refers to the shrinking of brain tissue and is typically seen in chronic conditions like **neurodegenerative diseases** or **long-standing severe malnutrition**.
- It does not explain the acute onset of lethargy and retinal hemorrhages immediately following a potential traumatic event in an otherwise healthy infant.
*Blood in the basal cisterns*
- **Blood in the basal cisterns** is characteristic of **subarachnoid hemorrhage**, which can be caused by ruptured aneurysms (rare in infants), arteriovenous malformations, or severe trauma.
- While abusive head trauma can sometimes cause subarachnoid bleeding, the primary finding in shaken baby syndrome is usually subdural hemorrhage, and retinal hemorrhages specifically point towards the shearing forces causing subdural bleeding.
*Multiple cortical and subcortical infarcts*
- **Multiple cortical and subcortical infarcts** indicate areas of brain tissue death due to **interrupted blood supply**, as seen in severe stroke or vasculitis.
- This is not the primary or most likely finding in abusive head trauma, though severe head trauma can sometimes lead to secondary ischemic injury due to increased intracranial pressure or vascular disruption.
Question 44: A 72-year-old man is brought to the physician by his wife for memory issues over the last 7 months. The patient's wife feels that he has gradually become more forgetful. He commonly misplaces his car keys and forgets his children's names. He seems to have forgotten how to make dinner and sometimes serves uncooked noodles or raw meat. One night he parked his car in a neighbor's bushes and was found wandering the street. He has a history of hypertension, hyperlipidemia, and COPD. Current medications include atorvastatin, metoprolol, ipratropium, and fluticasone. Vital signs are within normal limits. He is alert and oriented to person and place only. Neurologic examination shows no focal findings. His Mini-Mental State Examination score is 19/30. A complete blood count and serum concentrations of electrolytes, urea nitrogen, creatinine, thyroid-stimulating hormone, liver function tests, vitamin B12 (cobalamin), and folate are within the reference range. Which of the following is the most appropriate next step in diagnosis?
A. Electroencephalography
B. PET scan
C. MRI of the brain (Correct Answer)
D. Lumbar puncture
E. Neuropsychologic testing
Explanation: ***MRI of the brain***
- An **MRI of the brain** is crucial for evaluating **structural causes of cognitive impairment**, such as tumors, strokes, hydrocephalus, or significant atrophy that might explain the patient's rapidly progressing memory loss and functional decline.
- Given the patient's age, rapidly worsening dementia symptoms, and normal initial lab work, imaging is essential to rule out **reversible or treatable causes** and to characterize the extent of neurodegeneration.
*Electroencephalography*
- **EEG** is primarily used to detect **seizure activity** or to evaluate for rapidly progressive encephalopathies like Creutzfeldt-Jakob disease, which is not indicated by the patient's presentation.
- The patient's symptoms are consistent with a dementia syndrome, not acute encephalopathy or seizures.
*PET scan*
- A **PET scan** (e.g., FDG-PET or amyloid-PET) can provide information about metabolic activity or amyloid plaques, useful for **differentiating types of dementia** (e.g., Alzheimer's disease).
- However, it is an advanced test typically considered after structural imaging has ruled out other causes and when the diagnosis remains unclear.
*Lumbar puncture*
- **Lumbar puncture** is performed to analyze **cerebrospinal fluid (CSF)** for biomarkers (e.g., tau, Aβ42 levels) to help diagnose specific neurodegenerative diseases like Alzheimer's or to rule out infectious/inflammatory causes.
- It's usually reserved for cases where other investigations are inconclusive or specific conditions are strongly suspected, and structural imaging has been performed.
*Neuropsychologic testing*
- **Neuropsychologic testing** provides a detailed assessment of various cognitive domains and can help to **characterize the pattern and severity of cognitive impairment**.
- While valuable, it is usually performed after initial medical workup and structural imaging to understand the functional impact of any identified brain changes or to further delineate the type of cognitive disorder.
Question 45: A 27-year-old female presents to her primary care physician with a chief complaint of pain in her lower extremity. The patient states that the pain has gradually worsened over the past month. The patient states that her pain is worsened when she is training. The patient is a business student who does not have a significant past medical history and is currently not on any medications. She admits to having unprotected sex with multiple partners and can not recall her last menses. She drinks 7 to 10 shots of liquor on the weekends and smokes marijuana occasionally. She recently joined the cross country team and has been training for an upcoming meet. Her temperature is 99.5°F (37.5°C), pulse is 88/min, blood pressure is 100/70 mmHg, respirations are 10/min, and oxygen saturation is 97% on room air. On physical exam you note a very pale young woman in no current distress. Pain is localized to the lateral aspect of the knee and is reproduced upon palpation. Physical exam of the knee, hip, and ankle is otherwise within normal limits. The patient has 1+ reflexes and 2+ strength in all extremities. A test for STI's performed one week ago came back negative for infection. Which of the following is the most likely explanation for this patient's presentation?
A. Infection of the joint space
B. Friction with the lateral femoral epicondyle (Correct Answer)
C. Cartilaginous degeneration from overuse
D. Meniscal tear
E. Cartilaginous degeneration from autoimmunity
Explanation: ***Friction with the lateral femoral epicondyle***
- The patient's presentation of **lateral knee pain**, worsening with activity (cross-country training), and localized tenderness suggests **iliotibial band syndrome (ITBS)**.
- ITBS results from repetitive friction of the **iliotibial band** over the **lateral femoral epicondyle** during knee flexion and extension, common in runners.
*Infection of the joint space*
- While the patient has a low-grade fever, there are no other signs of **septic arthritis**, such as **swelling**, **warmth**, **erythema**, or significant pain at rest.
- Furthermore, a recent STI test was negative, and the pain is localized to the lateral aspect, not primarily within the joint.
*Cartilaginous degeneration from autoimmunity*
- There are no symptoms or signs to suggest an **autoimmune condition**, such as **morning stiffness**, **symmetrical joint involvement**, or other systemic symptoms.
- The pain is localized and activity-related, not typical of autoimmune arthritis.
*Cartilaginous degeneration from overuse*
- **Cartilaginous degeneration (osteoarthritis)** due to overuse is less likely in a 27-year-old without a history of significant trauma or predisposing factors.
- While overuse contributes to ITBS, direct cartilaginous degeneration typically presents with more diffuse pain or crepitus within the joint.
*Meniscal tear*
- A **meniscal tear** would typically cause **mechanical symptoms** like **clicking**, **locking**, or **catching** of the knee, which are not described.
- Pain from a meniscal tear is generally localized to the **joint line** (medial or lateral) and not specifically to the lateral femoral epicondyle.
Question 46: A 45-year-old woman comes to the emergency department because of right upper abdominal pain and nausea that have become progressively worse since eating a large meal 8 hours ago. She has had intermittent pain similar to this before, but it has never lasted this long. She has a history of hypertension and type 2 diabetes mellitus. She does not smoke or drink alcohol. Current medications include metformin and enalapril. Her temperature is 38.5°C (101.3°F), pulse is 90/min, and blood pressure is 130/80 mm Hg. The abdomen is soft, and bowel sounds are normal. The patient has sudden inspiratory arrest during right upper quadrant palpation. Laboratory studies show a leukocyte count of 13,000/mm3. Serum alkaline phosphatase, total bilirubin, amylase, and aspartate aminotransferase levels are within the reference ranges. Imaging is most likely to show which of the following findings?
A. Dilated common bile duct with intrahepatic biliary dilatation
B. Enlargement of the pancreas with peripancreatic fluid
C. Gallstone in the cystic duct (Correct Answer)
D. Gas in the gallbladder wall
E. Decreased echogenicity of the liver
Explanation: ***Gallstone in the cystic duct***
- The patient's presentation with **right upper quadrant pain** after a fatty meal, **nausea**, **fever**, **leukocytosis**, and a positive **Murphy's sign** (inspiratory arrest during palpation) is highly suggestive of **acute cholecystitis**.
- **Acute cholecystitis** is most commonly caused by an obstructing gallstone in the **cystic duct**, leading to inflammation of the gallbladder.
*Dilated common bile duct with intrahepatic biliary dilatation*
- This finding suggests **choledocholithiasis** (gallstone in the common bile duct) or another obstruction of the common bile duct, which would typically cause **elevated bilirubin** and **alkaline phosphatase**.
- These laboratory values are **within normal limits** for this patient, making choledocholithiasis less likely.
*Enlargement of the pancreas with peripancreatic fluid*
- These findings are characteristic of **acute pancreatitis**, which would present with elevated **amylase** and **lipase**.
- The patient's **amylase level is normal**, ruling out acute pancreatitis as the primary diagnosis.
*Gas in the gallbladder wall*
- This indicates **emphysematous cholecystitis**, a severe form of acute cholecystitis typically seen in elderly or immunocompromised patients, often with diabetes.
- While the patient has diabetes, the overall clinical picture does not specifically point to this more advanced and rare complication, and it's not the *most likely* initial finding for typical acute cholecystitis.
*Decreased echogenicity of the liver*
- Decreased echogenicity of the liver is typically associated with conditions like **fatty liver disease** or **hepatitis**.
- While the patient has risk factors for fatty liver (type 2 diabetes), this finding does not explain her acute symptoms of right upper quadrant pain, fever, and Murphy's sign, which point towards gallbladder pathology.
Question 47: A 51-year-old homeless man presents to the emergency department with severe abdominal pain and cramping for the past 3 hours. He endorses radiation to his back. He adds that he vomited multiple times. He admits having been hospitalized repeatedly for alcohol intoxication and abdominal pain. His temperature is 103.8° F (39.8° C), respiratory rate is 15/min, pulse is 107/min, and blood pressure is 100/80 mm Hg. He refuses a physical examination due to severe pain. Blood work reveals the following:
Serum:
Albumin: 3.2 gm/dL
Alkaline phosphatase: 150 U/L
Alanine aminotransferase: 76 U/L
Aspartate aminotransferase: 155 U/L
Gamma-glutamyl transpeptidase: 202 U/L
Lipase: 800 U/L
What is the most likely diagnosis of this patient?
A. Duodenal peptic ulcer
B. Choledocholithiasis
C. Pancreatitis (Correct Answer)
D. Cholecystitis
E. Gallbladder cancer
Explanation: ***Pancreatitis***
- The patient's history of **repeated alcohol intoxication** and abdominal pain, combined with **severe abdominal pain radiating to the back**, vomiting, and significantly elevated **lipase (800 U/L)**, are highly indicative of **acute pancreatitis**.
- The elevated **liver enzymes (ALT, AST, GGT)** and **alkaline phosphatase** can be associated with cholestasis or liver involvement often seen in alcohol-induced pancreatitis or can be elevated due to a gallstone lodged in the common bile duct, which is also a common cause of pancreatitis.
*Duodenal peptic ulcer*
- While duodenal ulcers cause severe abdominal pain, they typically present with **epigastric pain** that may be relieved by food, and often cause **melena or hematemesis** if bleeding.
- The extremely high **lipase level** and pain radiating to the back are not characteristic of an uncomplicated duodenal ulcer.
*Choledocholithiasis*
- **Choledocholithiasis** (gallstones in the common bile duct) can cause severe right upper quadrant or epigastric pain and elevated liver enzymes, but it doesn't typically present with an isolated, dramatically high **lipase** level without concomitant pancreatitis.
- The main symptom is **biliary colic**, often post-prandial, and usually involves jaundice or cholangitis if infected.
*Cholecystitis*
- **Cholecystitis** presents with **right upper quadrant pain**, often radiating to the shoulder, associated with fever and nausea, and is usually triggered by fatty meals.
- Although there might be some elevation in liver enzymes and amylase/lipase, the **markedly elevated lipase** and pain radiating to the back are more suggestive of pancreatitis.
*Gallbladder cancer*
- **Gallbladder cancer** typically presents with more insidious symptoms, such as chronic right upper quadrant pain, weight loss, jaundice, and anorexia.
- It would not usually present with an acute episode of **severe abdominal pain and drastically high lipase** in this manner.
Question 48: A previously healthy 18-year-old woman comes to the physician because of a 2-day history of swelling and itchiness of her mouth and lips. It decreases when she eats cold foods such as frozen fruit. Four days ago, she underwent orthodontic wire-placement on her upper and lower teeth. Since then, she has been taking ibuprofen twice daily for the pain. For the past 6 months, she has been on a strict vegan diet. She is sexually active with one partner and uses condoms consistently. She had chickenpox that resolved spontaneously when she was 6 years old. Her vitals are within normal limits. Examination shows diffuse erythema and edema of the buccal mucosa with multiple serous vesicles and shallow ulcers. Stroking the skin with pressure does not cause blistering of the skin. The remainder of the examination shows no abnormalities. Which of the following is the most likely cause of these symptoms?
A. Vitamin deficiency
B. Dermatitis herpetiformis
C. Allergic contact dermatitis (Correct Answer)
D. Reactivation of varicella zoster virus
E. Herpes labialis
Explanation: ***Allergic contact dermatitis***
- The symptoms of **swelling, itchiness**, and **erythema of the buccal mucosa** with vesicles and shallow ulcers, occurring after orthodontic wire placement, strongly suggest an allergic reaction to materials in the wires (e.g., nickel).
- The improvement with **cold foods** (vasoconstriction and soothing effect) and the absence of skin blistering with pressure (differentiating from bullous diseases) further support this diagnosis.
*Vitamin deficiency*
- While a **vegan diet** can predispose to certain vitamin deficiencies (e.g., B12), the sudden onset of localized oral swelling and itchiness is not typical.
- Oral manifestations of vitamin deficiencies usually develop chronically and involve conditions like **glossitis, angular cheilitis, or stomatitis**, rather than acute localized swelling and vesicles.
*Dermatitis herpetiformis*
- This condition is characterized by intensely pruritic, vesicular lesions, primarily on **extensor surfaces** (elbows, knees, buttocks), and is strongly associated with **celiac disease**.
- Oral lesions are uncommon, and the lack of systemic GI symptoms or characteristic skin distribution makes this diagnosis less likely.
*Reactivation of varicella zoster virus*
- Reactivation (shingles) typically causes a **unilateral, dermatomal rash** with painful vesicles, usually occurring in older or immunocompromised individuals.
- The patient's age and healthy status, along with the bilateral involvement of the mouth and lips, do not fit the typical presentation of zoster reactivation.
*Herpes labialis*
- Caused by **Herpes Simplex Virus (HSV)**, it presents as clusters of painful vesicles, typically on the **lips or perioral region**.
- While vesicles are present, the diffuse erythema and edema of the buccal mucosa and the clear association with orthodontic hardware placement make allergic contact dermatitis a more likely etiology.
Question 49: A 36-year-old woman is brought to the emergency room by her husband for “weird behavior" for the past several weeks. He reports that her right arm has been moving uncontrollably in a writhing movement and that she has been especially irritable. She has a history of depression, which was diagnosed 4 years ago and is currently being treated with sertraline. She denies any recent fever, trauma, infections, travel, weakness, or sensory changes. She was adopted so is unsure of her family history. Which of the following is the most likely explanation for her symptoms?
A. Frontotemporal lobe degeneration
B. Presence of misfolded proteins in the brain
C. Development of intracellular eosinophilic inclusions
D. CAG triplet expansion on chromosome 4 (Correct Answer)
E. GAA triplet expansion on chromosome 9
Explanation: ***CAG triplet expansion on chromosome 4***
- The patient's symptoms of **chorea** (uncontrolled writhing movements) and **irritability** (psychiatric changes) are classic manifestations of **Huntington's disease**.
- **Huntington's disease** is an autosomal dominant neurodegenerative disorder caused by a **CAG trinucleotide repeat expansion** on **chromosome 4** in the *HTT* gene.
*Frontotemporal lobe degeneration*
- **Frontotemporal dementia** typically presents with prominent behavioral changes (disinhibition, apathy) or language difficulties (aphasia), but **chorea** is not a characteristic feature.
- While psychiatric symptoms can occur, the specific motor dysfunction described points away from isolated frontotemporal degeneration.
*Presence of misfolded proteins in the brain*
- While **Huntington's disease** does involve misfolded huntingtin protein, this answer choice is too general and could apply to many neurodegenerative diseases like Alzheimer's (beta-amyloid, tau) or Parkinson's (alpha-synuclein).
- It does not specify the unique genetic basis directly responsible for the observed symptoms in this case.
*Development of intracellular eosinophilic inclusions*
- **Intracellular eosinophilic inclusions**, specifically **Lewy bodies**, are characteristic of **Parkinson's disease** and **Lewy body dementia**.
- These conditions primarily present with parkinsonism or dementia, not the prominent choreiform movements seen in this patient.
*GAA triplet expansion on chromosome 9*
- A **GAA triplet expansion on chromosome 9** is the genetic cause of **Friedreich's ataxia**, an autosomal recessive disorder.
- Friedreich's ataxia typically presents with progressive **ataxia**, dysarthria, and loss of proprioception, not chorea or prominent psychiatric changes like irritability.
Question 50: Three days after undergoing laparoscopic colectomy, a 67-year-old man reports swelling and pain in his right leg. He was diagnosed with colon cancer 1 month ago. His temperature is 38.5°C (101.3°F). Physical examination shows swelling of the right leg from the ankle to the thigh. There is no erythema or rash. Which of the following is likely to be most helpful in establishing the diagnosis?
A. D-dimer level
B. Compression ultrasonography (Correct Answer)
C. CT pulmonary angiography
D. Transthoracic echocardiography
E. Blood cultures
Explanation: ***Compression ultrasonography***
- This patient's presentation with **unilateral leg swelling and pain** after surgery, especially given his recent **colon cancer diagnosis** (a hypercoagulable state), is highly suspicious for a **deep vein thrombosis (DVT)**.
- **Compression ultrasonography** is the gold standard, non-invasive imaging modality for diagnosing DVT, allowing direct visualization of thrombi and assessing venous compressibility.
*D-dimer level*
- While a **positive D-dimer** indicates recent or ongoing clot formation, it is **non-specific** and can be elevated in many conditions, including surgery, cancer, and infection.
- A normal D-dimer can rule out DVT in low-probability patients, but a high D-dimer in a high-probability patient (like this case) requires further imaging for confirmation, making it less definitive than ultrasound.
*CT pulmonary angiography*
- This imaging is used to diagnose a **pulmonary embolism (PE)**, which is a complication of DVT, but the primary symptoms here are localized to the leg.
- While PE is a concern, diagnosing the source (DVT) in the leg is the immediate priority for treatment and prevention of future complications.
*Transthoracic echocardiography*
- **Echocardiography** evaluates cardiac structure and function and can sometimes detect large clots in the right heart leading to PE, but it is not the primary diagnostic tool for DVT in the leg.
- It would be done if signs of cardiac strain or shunting associated with acute PE were prominent, which is not the case here.
*Blood cultures*
- **Blood cultures** are used to diagnose **bacteremia or sepsis**, which might explain a fever, but the prominent, unilateral leg swelling and pain are not typical for a primary infectious cause in the leg without local signs of cellulitis or abscess.
- While a low-grade fever is present, the absence of erythema or rash makes a primary infectious etiology less likely than DVT given the risk factors.
