10 USMLE Step 1 Mixed Review Questions with Answers (Set 5)

These 10 quick USMLE review questions test high-yield facts that show up again and again on the exam: splenic trauma, diverticular disease, mesenteric ischemia, Dubin-Johnson syndrome, Crohn disease, porphyria cutanea tarda, melanoma, scaphoid fractures, sprains and Lyme disease. Each question includes the correct answer.

Written by Dr. Ray Makar, MD, author of the Repeated USMLE Questions eBook series.

Prefer video? Watch daily USMLE case questions on MedFocus by Dr. Ray on YouTube.

How to use this page: read the question, pick your answer, then tap Show Answer and Explanation.

Questions

Question 1. Which of the following organs is the most commonly affected by a blunt trauma to the abdomen?

A- Large intestine
B- Liver
C- Small intestine
D- Spleen

D- Spleen- The spleen is the most commonly injured organ in blunt abdominal trauma because of its location and rich blood supply. Liver injuries also occur, but less frequently. The intestines are less commonly affected.
The correct answer is D

 

Question 2. Which of the following is the most common complication of diverticulosis?

A- Bleeding
B- Diverticulitis
C- Obstruction
D- Perforation

B- Diverticulitis- The most common complication of diverticulosis is diverticulitis, which occurs when diverticula become inflamed or infected. Bleeding, obstruction, and perforation can occur but are less common overall.
The correct answer is B

 

Question 3. Which of the following is the most common cause of acute mesenteric ischemia?

A- Abdominal aortic aneurysm
B- Embolism
C- Mesenteric vein thrombosis
D- Vascular autoimmune disease

B- Embolism- The most common cause of acute mesenteric ischemia is a superior mesenteric artery embolism, often originating from the heart (e.g., atrial fibrillation). Mesenteric vein thrombosis and autoimmune vasculitis are less common causes.
The correct answer is B

 

Question 4. Which of the following differentiates Dubin-Johnson syndrome from Rotor syndrome?

A- Black pigmentation of the liver
B- Conjugated hyperbilirubinemia
C- Level of liver enzymes
D- Mode of inheritance

A- Black pigmentation of the liver- Both Dubin–Johnson and Rotor syndromes cause conjugated hyperbilirubinemia and have similar inheritance patterns. The key distinguishing feature is that Dubin–Johnson syndrome shows dark, black liver pigmentation, while Rotor syndrome does not.
The correct answer is A

 

Question 5. Which one of the following features characterizes Crohn’s disease from ulcerative colitis?

A- Bloody diarrhea
B- Colectomy is curative
C- Continuous disease beginning at the rectum and extending without skipped areas
D- Perineal fissures and fistulas

D- Perineal fissures and fistulas- Crohn’s disease is characterized by transmural inflammation, which often leads to perineal fissures and fistulas. Bloody diarrhea and continuous rectal involvement with curative colectomy are features more typical of ulcerative colitis.
The correct answer is D

 

Question 6. Which of the following conditions is characterized by painless blisters on the back of the hands with friable surrounding skin and hyperpigmentation of the face?

A- Contact dermatitis
B- Dermatitis herpetiformis
C- Herpes Zoster
D- Porphyria cutanea tarda

D- Porphyria cutanea tarda- Porphyria cutanea tarda presents with painless blisters on sun-exposed areas, especially the backs of the hands, along with fragile skin and facial hyperpigmentation. The other conditions have different clinical patterns and do not produce this combination of findings.
The correct answer is D

 

Question 7. Which of the following is the best next step for a suspicious malignant melanoma?

A- Excisional biopsy
B- Excision with a safety margin
C- Observation
D- Shave biopsy

A- Excisional biopsy- For a lesion suspicious for malignant melanoma, the best next step is excisional biopsy with narrow margins to allow accurate diagnosis and depth measurement (Breslow thickness). Wide excision is done only after confirming the diagnosis. Shave biopsy and observation are inappropriate for suspected melanoma.
The correct answer is A

 

Question 8. Which one of the following is the most appropriate next step in a suspected scaphoid fracture (with normal radiology)?

A- Admission and observation
B- Assurance and follow-up in 2 weeks
C- Emergent orthopedic consultation
D- Thumb spica splint

D- Thumb spica splint- A suspected scaphoid fracture can have normal initial X-rays, but the fracture may still be present. Because missed scaphoid fractures risk avascular necrosis, the correct step is to immobilize the wrist in a thumb spica splint and repeat imaging later.
The correct answer is D

 

Question 9. Which of the following is the correct statement about the difference between a strain and a sprain?

A- Strain affects ligaments, while a sprain affects muscles and tendons
B- Strain affects muscles or tendons, while a sprain affects ligaments
C- Strain affects muscles or ligaments, while a sprain affects tendons
D- Strain affects tendons and ligaments, while a sprain affects muscles

B- Strain affects muscles or tendons, while sprain affects ligaments- A strain is an injury to muscles or tendons (the structures that move bones). A sprain is an injury to ligaments, which connect bones and stabilize joints.
The correct answer is B

 

Question 10. Which of the following types of rashes characterizes Lyme disease?

A- Erythema marginatum
B- Erythema migrans
C- Erythema multiform
D- Erythematous maculopapular rash

B- Erythema migrans- Lyme disease classically presents with erythema migrans, a bull’s-eye rash that expands outward from the tick bite site. The other rashes are associated with different conditions.
The correct answer is B

 

High-yield points from this set

  • The spleen is the organ most often injured by blunt abdominal trauma.
  • Embolism is the most common cause of acute mesenteric ischemia.
  • Perianal fistulas point to Crohn disease.
  • Suspected scaphoid fracture: thumb spica splint even if the x-ray is normal.

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