WBR0327

Author	[[PageAuthor::Rim Halaby, M.D. [1] (Reviewed by Alison Leibowitz)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Pharmacology
Sub Category	SubCategory::Hematology
Prompt	[[Prompt::Brought by his parents, a 3-year-old African American male presents to the ER with irritability and swelling in the hands and feet. A peripheral smear (illustrated below) demonstrates findings consistent with the patient's condition. To relieve his symptoms, the patient is started on a chemotherapeutic agent. By which of the following mechanisms does the prescribed medication help relieve the patient's symptoms? ]]
Answer A	AnswerA::Increase in HbF levels
Answer A Explanation	AnswerAExp::Hydroxyurea is beneficial in patients with sickle cell disease (SCD) because it increases HbF levels.
Answer B	AnswerB::Decrease in thymidylate synthase activity
Answer B Explanation	AnswerBExp::5-Fluorouracil is known to inhibit thymidylate synthase.
Answer C	AnswerC::Increase in ribonucleotide reductase activity
Answer C Explanation	AnswerCExp::Hydroxyurea inhibits ribonucleotide reductase, which is not beneficial to patients with SCD.
Answer D	AnswerD::Increase in HbA levels
Answer D Explanation	AnswerDExp::Patients with SCD have low HbA levels, but hydroxyurea is beneficial in patients with sickle cell disease (SCD) because it increases HbF levels.
Answer E	AnswerE::Systemic vasodilatory effect
Answer E Explanation	AnswerEExp::Vasodilation is helpful for patients with SCD, but is not the mechanism by which hydroxyurea is beneficial.
Right Answer	RightAnswer::A
Explanation	[[Explanation::The patient in this scenario is most likely diagnosed with sickle cell disease. A peripheral smear demonstrates sickle-looking red blood cells, consistent with the diagnosis. Patients with sickle cell disease often require hydroxyurea, which provides symptomatic relief by increasing HbF levels. HbF has high affinity for oxygen and may aid in the delivery of oxygen to peripheral tissues in patients with SCD. Hydroxyurea is a chemotherapeutic agent that hinders ribonucleotide reductase ability to decrease DNA synthesis during S-phase. It is typically used to treat cancers, such as melanoma and CML. Common side effects of hydroxyurea include GI symptoms, bone marrow suppression, and an increased risk of developing leukemias. Educational Objective: Hydroxyurea often administered to patients with sickle cell disease in order to increase HbF levels. References: First Aid 2014 page 67]]
Approved	Approved::Yes
Keyword	WBRKeyword::HbF, WBRKeyword::hemoglobin, WBRKeyword::hemoglobinopathy, WBRKeyword::hemoglinopathies, WBRKeyword::sickle cell disease, WBRKeyword::peripheral, WBRKeyword::HbC, WBRKeyword::HbS, WBRKeyword::hydroxyurea
Linked Question	Linked::
Order in Linked Questions	LinkedOrder::