10 USMLE Internal Medicine Questions with Answers and Explanations (Set 1)

These 10 USMLE internal medicine practice questions mix endocrine, renal, rheumatology and pulmonary cases: thyroid storm, congenital adrenal hyperplasia, gout, fibromyalgia, acute tubular necrosis, acute intermittent porphyria, pyelonephritis, acid-base disorders and cystic fibrosis. Each question includes the correct answer and an explanation.

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. A 35-year-old unresponsive man is brought to the emergency room after an episode of agitation and confusion. He has a history of inadequately treated Graves’ disease. Physical examination reveals temperature of 102.5F. Blood pressure of 100/70 mm Hg, and pulse of 165 per minute. After stabilizing this patient, which of the following would be the best pharmacotherapy for treating his underlying condition?

A- Dobutamine
B- Iodine
C- Levothyroxine
D- Propylthiouracil
E- Warfarin

The patient is brought unconscious due to a medical emergency commonly known as a ‘thyroid storm’. It is a rare condition that occurs due to inadequate treatment of Graves disease and thyrotoxicosis. Once primary stabilization has been carried out, propylthiouracil or methimazole will be the best pharmacologic treatment as it will prevent the endogenous synthesis of thyroxine from taking place in the body, thus preventing worsening of the patient’s condition and hopefully preventing future episodes.
The correct answer is D

 

Question 2. A 4-year-old boy visits you in the clinic with his mother for evaluation of an increasing size of his genitalia. She tells you that her boy had aggressive behavior for the last six months. Besides progressive increase of the length of his penis, he has excessive pubic hair. On examination, his pulse is 80/min. and blood pressure is 140/92 mmHg. You send blood and urine samples for lab testing. What is the most likely initial diagnosis of this boy’s condition?

A- Conn syndrome
B- C-21 hydroxylase deficiency
C- C-11 hydroxylase deficiency
D- C-17 hydroxylase deficiency

This patient has a typical presentation of C-11 hydroxylase deficiency. It is manifested as hypertension, precocious puberty and abnormal behavior. This enzyme contributes to the transformation of 11-deoxycorticosterone into corticosterone which in turn forms aldosterone and also assists in the transformation of 11-deoxycortisol into cortisol. So, deficiency of this enzyme leads to lack of cortisone and aldosterone. 11-deoxycorticosterone has the same action as aldosterone on the kidneys leading to Na and water retention which results in high blood pressure. Deficiency of cortisol leads to adrenal hyperplasia due to feedback stimulation of ACTH. Increased secretion of sex hormones leads to precocious puberty.
Conn syndrome is familial hyperaldosteronism characterized by hypertension, hypokalemia and metabolic alkalosis. Sex hormones are not affected in this disorder.
C 21-hydroxylase deficiency results also in low cortisol and aldosterone and high secretion of sex hormones. It leads to hypotension and precocious puberty due to accumulation of progesterone and its transformation into testosterone by zona reticularis.
C 17-hydroxylase enzyme stimulates the transformation of pregnenolone and progesterone into sex hormones secreted by zona reticularis. Deficiency of this enzyme leads to hypertension and delayed puberty.
The correct answer is C

 

Question 3. A 56-year-old man presents to the clinic due to recurrent attacks of severe pain in his right big toe for the last few weeks. During the attacks, his toe becomes painful, red, warm and swollen. Significant improvement occurs after treatment with colchicine. Synovial fluid analysis is performed to confirm the diagnosis. What is the most likely finding to confirm the diagnosis?

A- Calcium oxalate crystals
B- Calcium pyrophosphate dihydrate crystals
C- Cholesterol crystals
D- Cloudy, reddish fluid, with leucocytes’ count equal to the blood count
E- Negatively birefringent urate crystals

This is a case of gout supported by the patient complaint of recurrent inflammation of the big toe and improvement of symptoms after the use of colchicine. Acute gout is confirmed by the detection of negatively birefringent monosodium urate crystals in synovial fluid analysis. Calcium pyrophosphate dihydrate crystals are found in cases of pseudo-gout. Acute arthritis is characterized by cloudy, bloody synovial fluid with leucocytes count equal to the blood count (normally synovial fluid may contain up to 200 cells /UL white blood cells). Cholesterol crystals are seen in patients with hypercholesterolemia and rheumatoid arthritis while calcium oxalate crystals can be seen in patient with renal diseases on dialysis.
The correct answer is E

 

Question 4. A 40-year-old woman complains of fatigue, headache and generalized pain for 9 months. She presented to the clinic several times and had multiple negative workups. Her pain started as localized to her head, neck and shoulder but now it is generalized. On physical examination, there are multiple points of tenderness on bony prominences. What is the most likely prognosis of this condition?

A- Symptomatic improvement with supportive therapy
B- Slow progression to permanent disability
C- Full recovery with specific medical therapy
D- Full recovery with multiple surgeries
E- Full recovery with radiation and chemotherapy

This is a classic presentation of fibromyalgia with multiple tender points and negative workup. Treatment of fibromyalgia is mainly symptomatic. There is no approved therapy or surgery that can lead to full recovery. Fibromyalgia is not accompanied by permanent disability.
The Correct Answer is A

 

Question 5. A 23-year-old woman was involved in a motor car accident three days ago. She was hypotensive and diagnosed with internal bleeding. She received several units of blood. Today her urine output is very low for the last six hours. Her urinalysis showed hematuria, proteinuria, muddy brown epithelial cells and granular casts. Her lab tests also show BUN: 26 mg/dL and serum creatinine: 2.6 mg/dL. What is the most likely diagnosis of her renal pathology?

A- Acute glomerulonephritis
B- Interstitial nephritis
C- Acute tubular necrosis
D- Traumatic avulsion of the ureter

Acute tubular necrosis (ATN) is the most likely pathology in this case. It is caused by decrease in blood volume which leads to prerenal azotemia. The most common cause of renal failure associated with prerenal azotemia is acute tubular necrosis. It is characterized by rapid decline of renal function and acute elevation of blood urea and serum creatinine. The BUN/creatinine ratio is usually normal as in this case. The muddy brown epithelial cells and granular casts are also typical in ATN. Acute glomerulonephritis is characterized by the humpy lumpy appearance under light microscope and sub epithelial humps under electron microscope. It is type III hypersensitivity forming immune complexes (antigen-antibody complexes) which deposit below the podocyte foot processes of the basement membrane of the glomeruli. It occurs mainly after streptococcal infection. Interstitial nephritis is inflammation of the kidney tissue that surrounds the tubules. It is caused mainly as a side effect of some drugs or post-infection. It is characterized by eosinophilia and eosinophiluria. Traumatic avulsion of the ureter is mainly occurs as a complication of ureteroscopy. There is no mention to any surgery or trauma of any kind in this patient’s history.
The correct answer is C

 

Question 6. A 14-year-old student is brought to the emergency room complaining of severe abdominal pain. Diagnostic tests reveal high serum levels of δ-aminolevulinate and porphobilinogen and low porphobilinogen deaminase (uroporphyrinogen I synthase) activity in red blood cells. Given the above test results, which of the following symptoms would be presented in this case?

A- Hypotension
B- Polyphagia
C- Neuropsychiatric disturbances
D- Stiff neck

Based on the laboratory results, we can conclude that the patient is suffering from acute intermittent porphyria (AIP). This condition is caused by deficiency of uroporphyrinogen I synthetase. High serum levels of porphobilinogen and δ-aminolevulinate (ALA) cause abdominal pain, high sympathetic tone, neuropathy, along with neuropsychiatric disturbances, which may include depression, seizures, anxiety, as well as paranoia. The condition most likely strikes after puberty.
The correct answer is C

 

Question 7. A 26-year-old woman complains of left flank pain and fever for 2 days. She has a history of two episodes of urinary tract infections in the past three years treated with trimethoprim-sulfamethoxazole. She is married, sexually active and takes contraceptive pills. Her last menstrual period was 5 days ago. On physical examination, her pulse is 100/min., blood pressure is 120/80 and her temperature is 103 F. She has left costovertebral angle tenderness on palpation. What is the best next step of management?

A- Admission to the intensive care unit (ICU)
B- Collection of urine and blood cultures
C- CT scan of abdomen and pelvis
D- MRI of the kidney
E- Administration of wide spectrum antibiotics

This patient history and clinical examination are consistent with acute pyelonephritis. Collection of urine and blood samples for culture should be done before administration of any antibiotics to achieve accurate results.. Culture is important for prescribing the most effective antibiotic and for the follow up. The patient is stable and so there is no need for the ICU. Diagnosis of acute pyelonephritis can be reached by history and physical examination only. Imaging studies are not necessary in this case as it is straight forward. In case of failure of medical treatment, imaging studies should be considered for further knowledge.
The correct answer is B

 

Question 8. A 32-year-old woman with a history of generalized anxiety disorder develops numbness of her face particularly around her mouth. Physical examination and x-ray show no abnormalities other than markedly increased respiratory rate. Laboratory investigations are as follows: PO2: 100 mmHg PCO2: 30 mmHg Bicarbonate: 18 mEq/L pH of blood: 7.51 Which of these findings shows that the body is compensating to this condition?

A- Elevated arterial PO2
B- Elevated hydrogen ion concentration
C- Elevated hydrogen ion excretion
D- Elevated bicarbonate excretion
E- Elevated respiratory rate

Respiratory alkalosis is the result of increased respiratory rate as in this patient. It is common in patients who suffer from anxiety disorders. The body compensates to it through renal mechanisms by decreased hydrogen ion excretion and decreased reabsorption of bicarbonate.
The correct answer is D

 

Question 9. A 12-year-old boy with a history of cystic fibrosis develops dyspnea, cough and fever. His temperature is 103.1 F, his pulse is 120/min and his oxygen saturation is 85%. Lung examination reveals bilateral rhonchi. What is the appropriate antibiotic treatment?

A- Ampicillin
B- Ampicillin and gentamicin
C- Ceftazidime
D- Ceftazidime and gentamicin
E- Vancomycin

This is a case of acute exacerbation of cystic fibrosis caused by pseudomonas aeruginosa infection which is the most common infection is cases of cystic fibrosis. Treatment with double coverage antibiotic therapy is appropriate in this case. Ceftazidime and gentamicin regime is the most effective antibiotic therapy for treatment of this infection.
The correct answer is D

 

Question 10. A 74-year-old man with a long history of emphysema presents to the office for a routine examination. He is complaining of fatigue and shortness of breath for 2 weeks. Physical examination is remarkable for scattered wheezes on both lung bases. Arterial blood gas is ordered for the patient. Which one of these results reflects the shift of oxygen dissociation curve to the right?

A- pH 7.00, bicarbonate 15, Pco2 60 and Po2 90
B- pH 7.05, bicarbonate 15, Pco2 30 and Po2 90
C- pH 7.47, bicarbonate 15, Pco2 30 and Po2 90
D- pH 7.50, bicarbonate 24, Pco2 40 and Po2 90
E- pH 7.60, bicarbonate 24, Pco2 60 and Po2 90

This patient has a long history of emphysema and respiratory distress. He exhibits respiratory acidosis due to defective gas exchange and shortness of breath. This condition is associated with shifting oxygen dissociation curve to the right. Shift to the right is caused by low pH, high Pco2 and low Po2.
The correct answer is A

 

High-yield points from this set

  • Thyroid storm: beta-blocker plus propylthiouracil first, then iodine an hour later.
  • Virilization with hypertension in a child = 11-beta-hydroxylase deficiency.
  • Gout: negatively birefringent needle-shaped monosodium urate crystals.
  • Fibromyalgia does not progress to disability; symptoms improve with exercise and supportive therapy.
  • Oliguria with muddy brown granular casts after shock = acute tubular necrosis.
  • Abdominal pain, neuropsychiatric symptoms and high ALA and porphobilinogen = acute intermittent porphyria.
  • Pyelonephritis: collect urine (and blood) cultures before antibiotics.
  • Respiratory alkalosis is compensated by the kidneys excreting bicarbonate.
  • Cystic fibrosis exacerbation (Pseudomonas): double coverage such as ceftazidime plus an aminoglycoside.
  • Acidosis, high CO2 and fever shift the oxygen dissociation curve to the right.

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