A 26-year-old woman presents with sudden-onset pain in her lower back. She says she was exercising in the gym several hours ago when she felt a sharp pain. The pain is radiating down the side of her leg and into her foot. On physical exam, her vital signs are as follows: HR 95, BP 120/70, T 37.2 degrees C. She has extreme pain shooting down her leg with a straight leg raise. Her sensation to light touch and pin-prick is intact throughout. Which of the following is the most likely diagnosis?
Q422
A 47-year-old man presents to the clinic with a 10-day history of a sore throat and fever. He has a past medical history significant for ulcerative colitis and chronic lower back pain. He smokes at least 1 pack of cigarettes daily for 10 years. The father of the patient died of colon cancer at the age of 50. He takes sulfasalazine and naproxen. The temperature is 38.9°C (102.0°F), the blood pressure is 131/87 mm Hg, the pulse is 74/min, and the respiratory rate is 16/min. On physical examination, the patient appears tired and ill. His pharynx is erythematous with exudate along the tonsillar crypts. The strep test comes back positive. In addition to treating the bacterial infection, what else would you recommend for the patient at this time?
Q423
A 31-year-old woman visits the clinic with chronic diarrhea on most days for the past four months. She also complains of lower abdominal discomfort and cramping, which is relieved by episodes of diarrhea. She denies any recent change in her weight. Bowel movements are preceded by a sensation of urgency, associated with mucus discharge, and followed by a feeling of incomplete evacuation. The patient went camping several months earlier, and another member of her camping party fell ill recently. Her temperature is 37° C (98.6° F), respiratory rate is 15/min, pulse is 67/min, and blood pressure is 122/98 mm Hg. Her physical examination is unremarkable. A routine stool examination is within normal limits and blood test results show:
Hb% 13 gm/dL
Total count (WBC): 11,000/mm3
Differential count:
Neutrophils: 70%
Lymphocytes: 25%
Monocytes: 5%
ESR: 10 mm/hr
What is the most likely diagnosis?
Q424
A 17-year-old boy is brought to the physician because of increasing pain and swelling of his right knee for 12 days. He has had episodes of pain with urination for 3 weeks. He had a painful, swollen left ankle joint that resolved without treatment one week ago. His mother has rheumatoid arthritis. He is sexually active with 2 female partners and uses condoms inconsistently. He appears anxious. His temperature is 38°C (100.4°F), pulse is 68/min, and blood pressure is 100/80 mm Hg. Examination shows bilateral inflammation of the conjunctiva. The right knee is tender, erythematous, and swollen; range of motion is limited by pain. There is tenderness at the left Achilles tendon insertion site. Genital examination shows no abnormalities. Laboratory studies show:
Hemoglobin 14.5 g/dL
Leukocyte count 12,300/mm3
Platelet count 310,000/mm3
Erythrocyte sedimentation rate 38 mm/h
Serum
Urea nitrogen 18 mg/dL
Glucose 89 mg/dL
Creatinine 1.0 mg/dL
Urine
Protein negative
Blood negative
WBC 12–16/hpf
RBC 1–2/hpf
An ELISA test for HIV is negative. Arthrocentesis is done. The synovial fluid is cloudy and a Gram stain is negative. Analysis of the synovial fluid shows a leukocyte count of 26,000/mm3 and 75% neutrophils. Which of the following is the most likely diagnosis?
Q425
A 75-year-old male is hospitalized for bloody diarrhea and abdominal pain after meals. Endoscopic work-up and CT scan lead the attending physician to diagnose ischemic colitis at the splenic flexure. Which of the following would most likely predispose this patient to ischemic colitis:
Q426
A 21-year-old woman presents with the complaints of nausea, vomiting, and diarrhea for 5 days. She adds that she has fever and abdominal cramping as well. She had recently attended a large family picnic and describes eating many varieties of cold noodle salads. Her past medical history is insignificant. Her temperature is 37.5°C (99.6°F), respiratory rate is 15/min, pulse is 67/min, and blood pressure is 92/68 mm Hg. Physical examination is non-contributory. Given the clinical information provided and most likely diagnosis, which of the following would be the next best step in the management of this patient?
Q427
A 23-year-old female is found by her roommate in her dormitory. The patient has a history of Type 1 Diabetes Mellitus and was binge drinking the night prior with friends at a local bar. The patient is brought to the emergency department, where vital signs are as follow: T 97.3 F, HR 119 bpm, BP 110/68 mmHg, RR 24, SpO2 100% on RA. On physical exam, the patient is clammy to touch, mucous membranes are tacky, and she is generally drowsy and disoriented. Finger stick glucose is 342 mg/dL; additional lab work reveals: Na: 146 K: 5.6 Cl: 99 HCO3: 12 BUN: 18 Cr: 0.74. Arterial Blood Gas reveals: pH 7.26, PCO2 21, PO2 102. Which of the following statements is correct regarding this patient's electrolyte and acid/base status?
Q428
A 37-year-old woman comes to the physician because of a 6-month history of weight loss, bloating, and diarrhea. She does not smoke or drink alcohol. Her vital signs are within normal limits. She is 173 cm (5 ft 8 in) tall and weighs 54 kg (120 lb); BMI is 18 kg/m2. Physical examination shows bilateral white spots on the temporal half of the conjunctiva, dry skin, and a hard neck mass in the anterior midline that does not move with swallowing. Urinalysis after a D-xylose meal shows a decrease in renal D-xylose excretion. Which of the following is most likely to have prevented this patient's weight loss?
Q429
A 35-year-old woman with a history of Crohn disease presents for a follow-up appointment. She says that lately, she has started to notice difficulty walking. She says that some of her friends have joked that she appears to be walking as if she was drunk. Past medical history is significant for Crohn disease diagnosed 2 years ago, managed with natalizumab for the past year because her intestinal symptoms have become severe and unresponsive to other therapies. On physical examination, there is gait and limb ataxia present. Strength is 4/5 in the right upper limb. A T1/T2 MRI of the brain is ordered and is shown. Which of the following is the most likely diagnosis?
Gastroenterology US Medical PG Practice Questions and MCQs
Question 421: A 26-year-old woman presents with sudden-onset pain in her lower back. She says she was exercising in the gym several hours ago when she felt a sharp pain. The pain is radiating down the side of her leg and into her foot. On physical exam, her vital signs are as follows: HR 95, BP 120/70, T 37.2 degrees C. She has extreme pain shooting down her leg with a straight leg raise. Her sensation to light touch and pin-prick is intact throughout. Which of the following is the most likely diagnosis?
A. Cauda equina syndrome
B. Ankylosing spondylitis
C. Osteomyelitis
D. Spinal stenosis
E. Disc herniation (Correct Answer)
Explanation: ***Disc herniation***
- The sudden onset of **sharp back pain** radiating down the leg (**radiculopathy**) after physical exertion, coupled with a positive **straight leg raise test**, is highly indicative of a disc herniation.
- Radiating pain suggests nerve root compression, and the straight leg raise test stretches the sciatic nerve, aggravating the pain in cases of disc herniation.
*Cauda equina syndrome*
- This is a neurological emergency characterized by **saddle anesthesia**, bowel or bladder dysfunction, and progressive motor weakness in both legs.
- These severe neurological deficits are not present in the patient's presentation; sensation is intact, and no mention of bowel/bladder issues.
*Ankylosing spondylitis*
- Typically presents with **chronic inflammatory back pain** that improves with exercise and worsens with rest, often in younger males.
- It is a systemic inflammatory condition, and the acute, exertion-related onset of pain with radiculopathy described here is not characteristic.
*Osteomyelitis*
- This is an **infection of the bone**, usually accompanied by fever, localized tenderness, and systemic signs of infection.
- The patient's vital signs are stable, and there is no indication of infection, making osteomyelitis less likely.
*Spinal stenosis*
- Characterized by **neurogenic claudication**, where leg pain and numbness worsen with walking and improve with sitting or leaning forward.
- The acute onset of pain after an intense activity and the presence of a positive straight leg raise are not typical features of spinal stenosis.
Question 422: A 47-year-old man presents to the clinic with a 10-day history of a sore throat and fever. He has a past medical history significant for ulcerative colitis and chronic lower back pain. He smokes at least 1 pack of cigarettes daily for 10 years. The father of the patient died of colon cancer at the age of 50. He takes sulfasalazine and naproxen. The temperature is 38.9°C (102.0°F), the blood pressure is 131/87 mm Hg, the pulse is 74/min, and the respiratory rate is 16/min. On physical examination, the patient appears tired and ill. His pharynx is erythematous with exudate along the tonsillar crypts. The strep test comes back positive. In addition to treating the bacterial infection, what else would you recommend for the patient at this time?
A. Fecal occult blood testing
B. Flexible sigmoidoscopy
C. Low-dose CT
D. PSA and digital rectal exam
E. Colonoscopy (Correct Answer)
Explanation: ***Colonoscopy***
- This patient has a history of **ulcerative colitis**, a condition known to increase the risk of **colorectal cancer**. Regular surveillance **colonoscopy** is recommended for these patients, especially with a family history of colon cancer.
- Furthermore, his father died of colon cancer at age 50, which strongly suggests a familial predisposition, making colonoscopy an urgent consideration for **cancer screening and prevention**.
*Fecal occult blood testing*
- While this test screens for **colorectal cancer**, it is generally **less sensitive and specific** than a colonoscopy, especially in high-risk individuals like this patient.
- It detects blood, which can be present due to various reasons, and a negative result does not reliably rule out **colorectal cancer** in someone with ulcerative colitis and a strong family history.
*Flexible sigmoidoscopy*
- This procedure examines only the **distal part of the colon**, which may miss lesions located in the **proximal colon**.
- For patients with **ulcerative colitis** who have an increased risk of pan-colonic cancer, a **full colonoscopy** is preferred for comprehensive surveillance.
*Low-dose CT*
- **Low-dose CT** is primarily used for **lung cancer screening** in heavy smokers, given this patient's 10-year, 1-pack-per-day history.
- While smoking is a risk factor for various cancers, it does not directly address the immediate and more significant risk for **colorectal cancer** related to his ulcerative colitis and family history.
*PSA and digital rectal exam*
- **PSA testing** and **digital rectal exams** are screening tools for **prostate cancer**.
- While important for men in a certain age range, there is **no indication** in the patient's history to suggest an urgent need for prostate cancer screening over colorectal cancer screening.
Question 423: A 31-year-old woman visits the clinic with chronic diarrhea on most days for the past four months. She also complains of lower abdominal discomfort and cramping, which is relieved by episodes of diarrhea. She denies any recent change in her weight. Bowel movements are preceded by a sensation of urgency, associated with mucus discharge, and followed by a feeling of incomplete evacuation. The patient went camping several months earlier, and another member of her camping party fell ill recently. Her temperature is 37° C (98.6° F), respiratory rate is 15/min, pulse is 67/min, and blood pressure is 122/98 mm Hg. Her physical examination is unremarkable. A routine stool examination is within normal limits and blood test results show:
Hb% 13 gm/dL
Total count (WBC): 11,000/mm3
Differential count:
Neutrophils: 70%
Lymphocytes: 25%
Monocytes: 5%
ESR: 10 mm/hr
What is the most likely diagnosis?
A. Giardiasis
B. Ulcerative colitis
C. Crohn’s disease
D. Irritable bowel syndrome (Correct Answer)
E. Laxative abuse
Explanation: ***Irritable bowel syndrome (IBS)***
- The patient's symptoms of chronic diarrhea, abdominal discomfort relieved by defecation, urgency, and incomplete evacuation, without significant weight loss or alarming signs, are highly characteristic of **Irritable Bowel Syndrome** meeting **Rome IV criteria**.
- The camping history suggests possible infectious gastroenteritis, but the **chronic duration (4 months)**, **normal stool examination**, and **absence of systemic illness** make infectious causes unlikely.
- The mild WBC elevation and normal ESR are non-specific findings; IBS is a **functional disorder** without inflammatory markers.
*Giardiasis*
- While giardiasis can cause chronic diarrhea, it often presents with **malabsorption symptoms** such as fatty stools, weight loss, and nutrient deficiencies.
- The routine stool examination being within normal limits makes giardiasis less likely, as **Giardia cysts or trophozoites** would typically be detected on microscopy.
*Ulcerative colitis*
- Ulcerative colitis is an **inflammatory bowel disease** typically characterized by bloody diarrhea, abdominal pain, and systemic symptoms like fever and weight loss.
- The patient's symptoms include the absence of blood in stools and no weight loss, with **normal ESR**, which makes ulcerative colitis unlikely.
*Crohn's disease*
- Crohn's disease is another **inflammatory bowel disease** that can affect any part of the GI tract and presents with chronic diarrhea, abdominal pain, and often systemic symptoms like weight loss, fever, or perianal disease.
- The lack of weight loss, systemic inflammation markers (normal ESR), and absence of blood or inflammatory markers in the stool make Crohn's disease less probable.
*Laxative abuse*
- Laxative abuse can cause chronic diarrhea, but it's typically associated with a history of **eating disorders** (anorexia nervosa, bulimia nervosa) or other psychological conditions, which are not mentioned in this case.
- The patient's description of abdominal discomfort relieved by defecation, urgency, and incomplete evacuation is more consistent with **IBS** (a functional bowel disorder) rather than solely laxative-induced diarrhea.
Question 424: A 17-year-old boy is brought to the physician because of increasing pain and swelling of his right knee for 12 days. He has had episodes of pain with urination for 3 weeks. He had a painful, swollen left ankle joint that resolved without treatment one week ago. His mother has rheumatoid arthritis. He is sexually active with 2 female partners and uses condoms inconsistently. He appears anxious. His temperature is 38°C (100.4°F), pulse is 68/min, and blood pressure is 100/80 mm Hg. Examination shows bilateral inflammation of the conjunctiva. The right knee is tender, erythematous, and swollen; range of motion is limited by pain. There is tenderness at the left Achilles tendon insertion site. Genital examination shows no abnormalities. Laboratory studies show:
Hemoglobin 14.5 g/dL
Leukocyte count 12,300/mm3
Platelet count 310,000/mm3
Erythrocyte sedimentation rate 38 mm/h
Serum
Urea nitrogen 18 mg/dL
Glucose 89 mg/dL
Creatinine 1.0 mg/dL
Urine
Protein negative
Blood negative
WBC 12–16/hpf
RBC 1–2/hpf
An ELISA test for HIV is negative. Arthrocentesis is done. The synovial fluid is cloudy and a Gram stain is negative. Analysis of the synovial fluid shows a leukocyte count of 26,000/mm3 and 75% neutrophils. Which of the following is the most likely diagnosis?
A. Lyme arthritis
B. Reactive arthritis (Correct Answer)
C. Rheumatoid arthritis
D. Septic arthritis
E. Syphilitic arthritis
Explanation: ***Reactive arthritis***
- The constellation of **urethritis** (painful urination), **conjunctivitis** (bilateral inflammation of the conjunctiva), and **arthritis** (knee pain, Achilles tendonitis) following a genitourinary infection in a sexually active young man is classic for reactive arthritis (formerly Reiter's syndrome).
- The synovial fluid analysis showing a **leukocyte count of 26,000/mm3** with **75% neutrophils** and a **negative Gram stain** is consistent with inflammatory, non-infectious arthritis.
*Lyme arthritis*
- This typically presents with **migratory polyarthritis** and often follows an **erythema chronicum migrans** rash, neither of which is present in this case.
- While Lyme disease can cause arthritis, the preceding urethritis and conjunctivitis are not characteristic features.
*Rheumatoid arthritis*
- Although the patient's mother has rheumatoid arthritis, this condition usually presents as **symmetric polyarthritis** primarily affecting small joints, and rarely involves urethritis or conjunctivitis.
- It would be unusual for a 17-year-old boy to present with seronegative rheumatoid arthritis with this specific triad of symptoms.
*Septic arthritis*
- While septic arthritis can cause a hot, swollen joint and fever, the **negative Gram stain** and absence of clear bacterial growth (implied by typical "reactive" presentation, although cultures are pending) make it less likely, especially with the conjunctivitis and urethritis.
- The history of preceding urethritis points towards a sterile inflammatory process rather than direct joint infection.
*Syphilitic arthritis*
- Syphilitic arthritis is rare and typically occurs in secondary or tertiary syphilis, presenting as a **chronic, destructive arthritis** often affecting large joints.
- The acute presentation with conjunctivitis and urethritis is not characteristic of syphilis.
Question 425: A 75-year-old male is hospitalized for bloody diarrhea and abdominal pain after meals. Endoscopic work-up and CT scan lead the attending physician to diagnose ischemic colitis at the splenic flexure. Which of the following would most likely predispose this patient to ischemic colitis:
A. Juxtaglomerular cell tumor
B. Hyperreninemic hyperaldosteronism secondary to type II diabetes mellitus
C. Obstruction of the abdominal aorta following surgery (Correct Answer)
D. Essential hypertension
E. Increased splanchnic blood flow following a large meal
Explanation: ***Obstruction of the abdominal aorta following surgery***
- A surgical procedure, especially one involving manipulation or clamping of the abdominal aorta, can lead to **reduced blood flow** to the intestinal arteries, making the **splenic flexure** particularly vulnerable to **ischemic colitis** due to its watershed area blood supply between the SMA and IMA territories.
- Reduced arterial flow to the colon results in **ischemia**, which causes inflammation, damage, and can present with bloody diarrhea and abdominal pain.
- Aortic surgery is a recognized risk factor for acute ischemic colitis due to interruption of mesenteric blood flow.
*Juxtaglomerular cell tumor*
- This tumor causes **renin-dependent hypertension**, leading to increased blood pressure, but does not directly cause **colonic ischemia**.
- Its primary effect is on the **renal blood vessels** and **fluid-electrolyte balance**, not intestinal circulation.
*Hyperreninemic hyperaldosteronism secondary to type II diabetes mellitus*
- This condition involves **high renin** and **aldosterone levels**, predisposing to hypertension and electrolyte imbalances, and is often a complication of **diabetes**, but it does not directly cause **ischemia of the colon**.
- While diabetes can cause microvascular complications, this specific presentation of **hyperaldosteronism** is not a direct cause of **ischemic colitis**.
*Essential hypertension*
- While **chronic hypertension** is a risk factor for generalized **atherosclerosis**, it is not as direct and acute a cause of **ischemic colitis** as a specific arterial obstruction.
- The effects of **essential hypertension** on the colon are often less acute and more diffuse than the localized ischemia experienced in this case.
*Increased splanchnic blood flow following a large meal*
- Postprandial **increased splanchnic blood flow** is a normal physiological response that facilitates digestion and nutrient absorption, and would not itself cause **ischemic colitis**.
- The postprandial pain in ischemic colitis occurs because the **diseased vasculature cannot meet increased metabolic demands** during digestion (supply-demand mismatch), not because the increased flow itself is harmful.
- In fact, reduced splanchnic blood flow due to underlying vascular disease, coupled with increased demand after meals, is the actual mechanism for **ischemic colitis** symptoms.
Question 426: A 21-year-old woman presents with the complaints of nausea, vomiting, and diarrhea for 5 days. She adds that she has fever and abdominal cramping as well. She had recently attended a large family picnic and describes eating many varieties of cold noodle salads. Her past medical history is insignificant. Her temperature is 37.5°C (99.6°F), respiratory rate is 15/min, pulse is 67/min, and blood pressure is 92/68 mm Hg. Physical examination is non-contributory. Given the clinical information provided and most likely diagnosis, which of the following would be the next best step in the management of this patient?
A. IV antibiotic therapy to prevent disseminated disease
B. Empiric therapy assuming multi-drug resistance
C. Prolonged oral antibiotics
D. Replacement of fluids and electrolytes (Correct Answer)
E. Short course of oral antibiotics to prevent asymptomatic carrier state
Explanation: ***Replacement of fluids and electrolytes***
- The patient presents with **nausea, vomiting, and diarrhea for 5 days**, along with **low blood pressure (92/68 mm Hg)**, indicating **dehydration** as the primary concern.
- **Fluid and electrolyte replacement** is crucial to correct dehydration and maintain vital organ function, especially in the setting of persistent gastrointestinal losses.
*IV antibiotic therapy to prevent disseminated disease*
- While foodborne illnesses can sometimes disseminate, the current presentation does not strongly suggest severe invasive disease requiring immediate IV antibiotics without further workup.
- Many common foodborne pathogens causing gastroenteritis are self-limiting, and antibiotics may not be beneficial or could even worsen outcomes (e.g., in E. coli O157:H7).
*Empiric therapy assuming multi-drug resistance*
- Initiating empiric multi-drug resistant therapy without identifying the causative agent or evidence of antibiotic failure is generally not recommended due to concerns about promoting resistance.
- The patient's symptoms are consistent with a common foodborne gastroenteritis, where supportive care is usually the first-line management.
*Prolonged oral antibiotics*
- **Prolonged oral antibiotics** are typically reserved for specific bacterial infections with identified pathogens requiring extended treatment or in immunocompromised patients.
- The given clinical picture primarily points to acute gastroenteritis requiring symptom management rather than a chronic or severe infection needing prolonged antibiotic courses.
*Short course of oral antibiotics to prevent asymptomatic carrier state*
- A short course of oral antibiotics to prevent an asymptomatic carrier state is typically considered for specific infections like **Typhoid fever** or in certain high-risk individuals, which is not the immediate concern here.
- In most cases of acute gastroenteritis, antibiotics are not given to prevent carrier states and may even prolong bacterial shedding in some Salmonella infections.
Question 427: A 23-year-old female is found by her roommate in her dormitory. The patient has a history of Type 1 Diabetes Mellitus and was binge drinking the night prior with friends at a local bar. The patient is brought to the emergency department, where vital signs are as follow: T 97.3 F, HR 119 bpm, BP 110/68 mmHg, RR 24, SpO2 100% on RA. On physical exam, the patient is clammy to touch, mucous membranes are tacky, and she is generally drowsy and disoriented. Finger stick glucose is 342 mg/dL; additional lab work reveals: Na: 146 K: 5.6 Cl: 99 HCO3: 12 BUN: 18 Cr: 0.74. Arterial Blood Gas reveals: pH 7.26, PCO2 21, PO2 102. Which of the following statements is correct regarding this patient's electrolyte and acid/base status?
A. The patient has an anion gap metabolic acidosis with decreased total body potassium (Correct Answer)
B. The patient has a metabolic acidosis with hyperkalemia from increased total body potassium
C. The patient has a non-anion gap metabolic acidosis with decreased total body sodium
D. The patient has an anion gap metabolic acidosis as well as a respiratory acidosis
E. The patient has a primary respiratory alkalosis with a compensatory metabolic acidosis
Explanation: ***The patient has an anion gap metabolic acidosis with decreased total body potassium***
- The **anion gap** is calculated as Na - (Cl + HCO3) = 146 - (99 + 12) = 35, which is significantly elevated (normal 8-12 mEq/L), indicating an **anion gap metabolic acidosis**. The low **pH (7.26)** and **HCO3 (12)** confirm metabolic acidosis.
- While the patient's serum potassium is **hyperkalemic (5.6 mEq/L)**, this is often a spurious finding in **diabetic ketoacidosis (DKA)** due to a shift of potassium out of cells in acidosis, masking significant **total body potassium depletion** from urinary losses.
*The patient has a metabolic acidosis with hyperkalemia from increased total body potassium*
- The patient clearly has a **metabolic acidosis** (low pH, low HCO3); however, the **hyperkalemia** observed is due to an extravasation of potassium from inside the cells to the extracellular fluid, as is common in **acidosis**.
- Despite the high serum potassium, the patient has overall **decreased total body potassium stores** because potassium is lost in the urine due to osmotic diuresis and shifts back into cells as acidosis resolves.
*The patient has a non-anion gap metabolic acidosis with decreased total body sodium*
- The calculated **anion gap of 35 mEq/L** is significantly elevated, meaning this is an **anion gap metabolic acidosis**, not a non-anion gap acidosis.
- The patient's serum sodium is 146 mEq/L, which is within the normal range to slightly elevated, and there is no evidence of **decreased total body sodium**.
*The patient has an anion gap metabolic acidosis as well as a respiratory acidosis*
- The patient has an **anion gap metabolic acidosis** with a low pH and HCO3; However, the **pCO2 is 21 mmHg**, which is lower than normal, indicating **respiratory compensation (respiratory alkalosis)** for the metabolic acidosis, not a respiratory acidosis.
- **Respiratory acidosis** would present with a high pCO2.
*The patient has a primary respiratory alkalosis with a compensatory metabolic acidosis*
- The **pH of 7.26 is acidic**, suggesting a primary acidosis, not a primary respiratory alkalosis.
- While the **pCO2 of 21 mmHg** indicates a respiratory alkalosis, it is acting as a **compensatory mechanism** for the primary metabolic acidosis, not the primary derangement.
Question 428: A 37-year-old woman comes to the physician because of a 6-month history of weight loss, bloating, and diarrhea. She does not smoke or drink alcohol. Her vital signs are within normal limits. She is 173 cm (5 ft 8 in) tall and weighs 54 kg (120 lb); BMI is 18 kg/m2. Physical examination shows bilateral white spots on the temporal half of the conjunctiva, dry skin, and a hard neck mass in the anterior midline that does not move with swallowing. Urinalysis after a D-xylose meal shows a decrease in renal D-xylose excretion. Which of the following is most likely to have prevented this patient's weight loss?
A. Tetracycline therapy
B. Lactose-free diet
C. Gluten-free diet (Correct Answer)
D. Mesalamine therapy
E. Pancreatic enzyme replacement
Explanation: ***Gluten-free diet***
- The patient's symptoms of **weight loss, bloating, diarrhea**, and **low BMI** (18 kg/m²) suggest **malabsorption**.
- **Bilateral white spots on the temporal conjunctiva (Bitot spots)** indicate **vitamin A deficiency**, a hallmark of fat-soluble vitamin malabsorption seen in **celiac disease**.
- The **hard neck mass that does not move with swallowing** suggests a **thyroid goiter**, likely related to **autoimmune thyroiditis**, which commonly co-occurs with celiac disease.
- **Decreased renal D-xylose excretion** confirms **proximal small bowel malabsorption**, characteristic of celiac disease where damaged villi cannot absorb D-xylose properly.
- A **gluten-free diet** is the definitive treatment for celiac disease and would have prevented the intestinal damage, malabsorption, and subsequent weight loss.
*Tetracycline therapy*
- **Tetracycline** treats **small intestinal bacterial overgrowth (SIBO)**, which can cause malabsorption and diarrhea.
- However, SIBO typically shows a **normal D-xylose test** (bacteria consume xylose before it's absorbed, but this usually doesn't significantly decrease excretion) or may show variable results.
- The presence of **Bitot spots** and **autoimmune thyroid involvement** strongly suggests celiac disease rather than SIBO.
*Lactose-free diet*
- **Lactose intolerance** causes bloating, gas, and diarrhea but typically **not significant weight loss** or **fat-soluble vitamin deficiencies**.
- The D-xylose test would be **normal** in lactose intolerance, as it tests small bowel absorptive capacity, not lactase enzyme activity.
- The widespread malabsorption with vitamin A deficiency extends beyond simple lactose intolerance.
*Mesalamine therapy*
- **Mesalamine** is an anti-inflammatory medication used to treat **inflammatory bowel disease (IBD)**, particularly **ulcerative colitis** and **Crohn's disease**.
- While Crohn's disease can cause small bowel malabsorption and weight loss, the **bilateral Bitot spots** and **positive D-xylose test** are more specific for **diffuse mucosal disease** like celiac disease.
- IBD would more likely present with bloody diarrhea, and the D-xylose test is typically normal unless extensive small bowel involvement.
*Pancreatic enzyme replacement*
- **Pancreatic enzyme replacement therapy (PERT)** treats **exocrine pancreatic insufficiency**, causing malabsorption, steatorrhea, and weight loss.
- Critically, the **D-xylose test is normal in pancreatic insufficiency** because D-xylose absorption does not require pancreatic enzymes—it depends solely on intact intestinal mucosa.
- The **decreased D-xylose excretion** in this patient indicates **small bowel mucosal damage**, not pancreatic dysfunction, ruling out pancreatic insufficiency.
Question 429: A 35-year-old woman with a history of Crohn disease presents for a follow-up appointment. She says that lately, she has started to notice difficulty walking. She says that some of her friends have joked that she appears to be walking as if she was drunk. Past medical history is significant for Crohn disease diagnosed 2 years ago, managed with natalizumab for the past year because her intestinal symptoms have become severe and unresponsive to other therapies. On physical examination, there is gait and limb ataxia present. Strength is 4/5 in the right upper limb. A T1/T2 MRI of the brain is ordered and is shown. Which of the following is the most likely diagnosis?
A. Sporadic Creutzfeldt-Jakob disease (sCJD)
B. West Nile encephalitis
C. Variant Creutzfeldt-Jakob disease (vCJD)
D. Subacute sclerosing panencephalitis (SSPE)
E. Progressive multifocal leukoencephalopathy (PML) (Correct Answer)
Explanation: ***Progressive multifocal leukoencephalopathy (PML)***
- This patient's history of **Crohn's disease** managed with **natalizumab** (a monoclonal antibody targeting α4-integrin) significantly increases the risk for **PML**, especially with new onset **ataxia** and **gait disturbance**. MRI findings would likely show multifocal, asymmetric white matter lesions without mass effect or enhancement.
- PML is caused by the **JC virus**, which reactivates in immunocompromised individuals, leading to demyelination and neurological deficits.
*Sporadic Creutzfeldt-Jakob disease (sCJD)*
- While sCJD presents with rapidly progressive **dementia**, **myoclonus**, and **ataxia**, it typically affects older individuals and is not directly linked to immunosuppression or natalizumab use.
- MRI findings in sCJD commonly show **cortical ribboning** or **basal ganglia hyperintensity** on DWI/FLAIR, which differs from PML's white matter lesions.
*West Nile encephalitis*
- This is an acute **viral infection** transmitted by mosquitoes, presenting with fever, headache, altered mental status, and sometimes movement disorders.
- It would typically have an **acute onset** and often characteristic seasonal and geographic patterns, which are not described here.
*Variant Creutzfeldt-Jakob disease (vCJD)*
- vCJD is linked to the consumption of **bovine spongiform encephalopathy (BSE)**-contaminated products and typically affects younger individuals with prominent psychiatric symptoms and sensory disturbances before neurological decline.
- It does not have a direct association with immunosuppressive therapy like natalizumab.
*Subacute sclerosing panencephalitis (SSPE)*
- SSPE is a rare, progressive neurological disorder that occurs years after a **measles infection**, primarily affecting children and young adults.
- Symptoms include intellectual deterioration, seizures, and myoclonus, but it is not associated with Crohn's disease, natalizumab, or the typical MRI findings for PML.
