Cover the key. Write the first action. Then open the rationale and name why the other choices fail.
Question 1
Levodopa should not be given to patients taking:
- A. Bromocriptine
- B. Monoamine oxydase A inhibitors
- C. Carbidopa
- D. Nonselective beta-adrenergic antagonists
Show answer and rationale
Correct answer: B — Monoamine oxydase A inhibitors
The correct answer is B: Monoamine oxidase A inhibitors. Levodopa should not be given concurrently with MAO-A inhibitors as they can potentiate the effects of levodopa, leading to an increased risk of hypertensive crisis. MAO-A inhibitors inhibit the breakdown of levodopa, causing an accumulation of dopamine in the brain. This combination can result in severe hypertension and other adverse effects.
Choice A (Bromocriptine) is incorrect because it is a dopamine agonist that can be used in combination with levodopa for Parkinson's disease treatment. Choice C (Carbidopa) is incorrect because it is often given in combination with levodopa to enhance its effectiveness by preventing its peripheral metabolism. Choice D (Nonselective beta-adrenergic antagonists) is incorrect as they do not have a direct interaction with levodopa.
Question 2
Effect of moderate consumption of alcohol on plasma lipoproteins is:
- A. Raising serum levels of high-density lipoproteins
- B. Increasing serum concentration of low-density lipoproteins
- C. Decreasing the concentration of high-density lipoproteins
- D. Raising serum levels of very low-density lipoproteins
Show answer and rationale
Correct answer: A — Raising serum levels of high-density lipoproteins
The correct answer is A because moderate alcohol consumption has been shown to raise serum levels of high-density lipoproteins (HDL), also known as "good" cholesterol. HDL helps remove other forms of cholesterol from the bloodstream, reducing the risk of cardiovascular disease. Increased HDL levels are associated with a lower risk of heart disease. On the other hand, choices B, C, and D are incorrect. Choice B, increasing low-density lipoproteins (LDL), is not a typical effect of moderate alcohol consumption and is associated with an increased risk of heart disease. Choice C, decreasing HDL levels, contradicts the known positive effect of alcohol on HDL. Choice D, raising very low-density lipoproteins (VLDL), is not a common result of moderate alcohol intake and is typically associated with an increased risk of heart disease.
Question 3
A 7-year-old boy presents with recent onset of vomiting and lethargy. Blood smear shows increased neutrophils with a left shift and 8% abnormal cells. Bone marrow contains 60% of the same cells. Flow cytometry shows that the cells are TdT–, CD10+, CD19+, CD20+, sIg+. What is the most likely diagnosis?
- A. Burkitt leukemia/lymphoma
- B. B-cell acute lymphoblastic leukemia (ALL)
- C. T-cell ALL
- D. Hematogones
Show answer and rationale
Correct answer: A — Burkitt leukemia/lymphoma
The correct answer is A: Burkitt leukemia/lymphoma. The key features in the case are increased neutrophils with a left shift, presence of abnormal cells in blood and bone marrow, and flow cytometry showing TdT–, CD10+, CD19+, CD20+, sIg+. These findings are consistent with Burkitt leukemia/lymphoma, a highly aggressive B-cell neoplasm. The presence of CD10, CD19, and CD20, along with sIg positivity, points towards a B-cell origin. Additionally, the characteristic translocation t(8;14) involving c-Myc oncogene is commonly seen in Burkitt lymphoma. The absence of TdT expression rules out T-cell ALL (Choice C). Hematogones (Choice D) are normal precursor B-cells found in bone marrow, but they do not typically present with the clinical features described. B-cell ALL (Choice B) lacks the specific features seen in this case
Question 4
A patient is scheduled for upcoming surgery. He is on nonsteroidal anti-inflammatory drugs (NSAIDs) for rheumatoid arthritis. You are being asked what to do with his medications for the surgery. What is the mechanism of action of NSAIDS?
- A. Irreversible inhibition of cyclooxygenase 1
- B. Irreversible inhibition of cyclooxygenase 2
- C. Reversible inhibition of cyclooxygenase 1
- D. Reversible inhibition of cyclooxygenase 2
Show answer and rationale
Correct answer: C — Reversible inhibition of cyclooxygenase 1
The correct answer is C: Reversible inhibition of cyclooxygenase 1. NSAIDs work by reversibly inhibiting cyclooxygenase enzymes, particularly COX-1 and COX-2, which are involved in the synthesis of prostaglandins. In this case, reversible inhibition is crucial because it allows for the temporary suppression of prostaglandin production, leading to pain relief and anti-inflammatory effects.
Explanation of other choices:
A: Irreversible inhibition of cyclooxygenase 1 - This is incorrect because NSAIDs typically do not irreversibly inhibit COX-1.
B: Irreversible inhibition of cyclooxygenase 2 - This is incorrect because NSAIDs do not irreversibly inhibit COX-2.
D: Reversible inhibition of cyclooxygenase 2 - This is incorrect because while NSAIDs can inhibit COX-2, the primary target is COX-1 for their therapeutic effects.
Question 5
A 2-month-old girl is found to have a small, hard mass on her scalp. The mass increases in size over the next 4 weeks. A biopsy is performed that confirms a diagnosis of embryonal rhabdomyosarcoma. You initiate chemotherapy with vincristine, dactinomycin, and cyclophosphamide. The child presents to clinic for day 1 of cycle 3 of chemotherapy, and the mass on her scalp is smaller. She is afebrile, absolute neutrophil count is 1,405 cells/mcL, platelet count is 154,000/mcL, and total bilirubin is 0.8 mg/dL. Her mother reports she looks very tired because her eyelids have been 'very droopy,' and she thinks she has a sore throat because her cry is hoarse. Her last bowel movement was 2 days ago. What is the most appropriate chemotherapy plan?
- A. Continue vincristine, dactinomycin, and cyclophosphamide at full dosage.
- B. Do not administer any chemotherapy; rhabdomyosarcoma is progressing and she needs different therapy.
- C. Administer dactinomycin and cyclophosphamide but hold the vincristine and reevaluate weekly. If the ptosis and hoarse cry resolve, vincristine can be resumed with a dose reduction and, if tolerated, re-escalated to the full dose in the future.
- D. Administer dactinomycin and cyclophosphamide but discontinue vincristine permanently.
Show answer and rationale
Correct answer: C — Administer dactinomycin and cyclophosphamide but hold the vincristine and reevaluate weekly. If the ptosis and hoarse cry resolve, vincristine can be resumed with a dose reduction and, if tolerated, re-escalated to the full dose in the future.
The correct answer is C: Administer dactinomycin and cyclophosphamide but hold the vincristine and reevaluate weekly. If the ptosis and hoarse cry resolve, vincristine can be resumed with a dose reduction and, if tolerated, re-escalated to the full dose in the future.
Rationale:
1. Ptosis and hoarse cry are symptoms of vincristine-induced neurotoxicity.
2. Holding vincristine allows for resolution of these side effects.
3. Reevaluating weekly ensures close monitoring of symptoms.
4. If symptoms resolve, vincristine can be cautiously reintroduced with a dose reduction to prevent further neurotoxicity.
Summary:
A: Continuing all chemotherapy may worsen neurotoxicity.
B: Withholding all chemotherapy is not appropriate if two agents are effective.
D: Discontinuing vincristine permanently may limit treatment options.
