Antimetabolites (azathioprine, mycophenolate) — MCQs

A 24-year-old woman of Ashkenazi Jewish descent presents with recurrent bloody diarrhea and abdominal pain. She says she feels well otherwise. Review of systems is significant for a 4 kg weight loss over the past month. Physical examination is significant for multiple aphthous oral ulcers. Colonoscopy reveals a cobblestone pattern of lesions of the mucosa of the intestinal wall with skip lesions involving the terminal ileum and colon. The patient is informed of the diagnosis and medication to treat her condition is prescribed. On a follow-up visit 6 weeks later, the patient presents with non-productive cough, chest pain, dyspnea on exertion, and worsening oral lesions. A chest radiograph reveals a diffuse interstitial pattern. Which of the following enzymes is inhibited by the medication most likely prescribed for her initial diagnosis?

A 3-month-old boy is brought to the pediatrician by his mother after she notices orange sand–like crystalline material in her child’s diaper. He is not currently taking any medication and is exclusively breastfed. His immunizations are up to date. The doctor tells the mother that her son may have an X-linked recessive disorder. The boy is prescribed a medication that inhibits an enzyme responsible for the production of the crystals seen in his urine microscopy. Which of the following enzymes is the target of this medication?

A 54-year-old woman presents with acute pain in her left toe. She says she hasn't been able to wear closed shoes for 2 weeks. Past medical history is significant for gastroesophageal reflux disease, diagnosed 2 years ago. The patient is afebrile and vital signs are within normal limits. Her BMI is 31 kg/m2. On physical examination, the left toe is warm to touch, swollen, and erythematous. A joint fluid aspiration from the left toe is performed and shows needle-shaped negatively birefringent urate crystals. The patient is started on methotrexate for gout prophylaxis. On her follow-up visit 6 weeks later, she has an elevated homocysteine level, a decreased serum folic acid level, and a normal methylmalonic acid level. Which of the following drugs would most likely cause a similar side effect to that seen in this patient?

An investigator is studying a drug that acts on the thyroid hormone pathway. Levels of serum free T3 and T4 in healthy participants are measured before and after administration of the drug. After administration, there is a decrease in the average serum free T3 level, while the average serum free T4 level is increased compared to initial serum studies. Inhibition of which of the following is the most likely mechanism of action of this drug?

A 68-year-old woman comes to the physician for a follow-up examination. Three months ago, she underwent heart transplantation for restrictive cardiomyopathy and was started on transplant rejection prophylaxis. Her pulse is 76/min and blood pressure is 148/82 mm Hg. Physical examination shows enlargement of the gum tissue. There is a well-healed scar on her chest. Serum studies show hyperlipidemia. The physician recommends removing a drug that decreases T cell activation by inhibiting the transcription of interleukin-2 from the patient's treatment regimen and replacing it with a different medication. Which of the following drugs is the most likely cause of the adverse effects seen in this patient?

A drug that inhibits mRNA synthesis has the well-documented side effect of red-orange body fluids. For which of the following is this drug used as monotherapy?

A 26-year-old G1P0 woman is brought to the emergency room by her spouse for persistently erratic behavior. Her spouse reports that she has been sleeping > 1 hour a night, and it sometimes seems like she’s talking to herself. She has maxed out their credit cards on baby clothes. The patient’s spouse reports this has been going on for over a month. Since first seeing a physician, she has been prescribed multiple first and second generation antipsychotics, but the patient’s spouse reports that her behavior has failed to improve. Upon examination, the patient is speaking rapidly and occasionally gets up to pace the room. She reports she is doing “amazing,” and that she is “so excited for the baby to get here because I’m going to be the best mom.” She denies illicit drug use, audiovisual hallucinations, or suicidal ideation. The attending psychiatrist prescribes a class of medication the patient has not yet tried to treat the patient’s psychiatric condition. In terms of this new medication, which of the following is the patient’s newborn most likely at increased risk for?

A 6-month-old infant boy is brought to the clinic for a check-up by a couple who recently adopted him from foster care. The biological mother was from a rehabilitation facility and was found incompetent to care for the child, hence he was handed over to foster care. No other information is available regarding his prenatal or birth history. On examination, his weight is found to be below the 3rd percentile. Physical appearance is remarkable for midfacial hypoplasia with a flattened nasal bridge, smooth philtrum, and thin lips. Auscultation reveals a grade 3/6 holosystolic murmur at the left lower sternal border. Developmental delay is noted as well. Which of the following teratogens is most likely to be associated with the infant's presentation?

A 44-year-old man, with a history of intravenous (IV) drug use, presented to the emergency department due to worsening non-productive cough, exertional dyspnea, and night sweats. His cough started 3 weeks ago and progressively worsened. He is homeless and well-known by the hospital staff. He was previously admitted to the hospital after an overdose of opioids. He takes no medication. At the hospital, the vital signs included: blood pressure 101/68 mm Hg, heart rate 99/min, respiratory rate 20/min, oxygen saturation of 91% on room air, and oral temperature of 37.4°C (99.3°F). His chest X-ray showed left perihilar shadowing. The laboratory results included: WBC count 8,800/mm3 Arterial pH 7.39 Rapid HIV testing positive with an elevated viral load PaCO2 41 mm Hg PaO2 76 mm Hg He was admitted for the treatment of presumed sepsis and pneumonia, and he was immediately started on IV ceftriaxone. An induced sputum specimen shows multiple kidney bean-shaped cysts that are approximately 5 um. These cysts stain positive with methenamine silver. What is the preferred antibiotic therapeutic regimen for this condition?

A 59-year-old man presents with intense, sharp pain in his toe for the past hour. He reports similar symptoms in the past and this is his 2nd visit to the emergency department this year with the same complaint. The patient is afebrile and the vital signs are within normal limits. On physical examination, there is significant erythema, swelling, warmth, and moderate pain on palpation of the right 1st toe. The remainder of the examination is unremarkable. A plain radiograph of the right foot reveals no abnormalities. Joint arthrocentesis of the inflamed toe reveals urate crystals. Laboratory studies show: Serum glucose (random) 170 mg/dL Sodium 140 mEq/L Potassium 4.1 mEq/L Chloride 100 mEq/L Uric acid 7.2 mg/dL Serum creatinine 0.8 mg/dL Blood urea nitrogen 9 mg/dL Cholesterol, total 170 mg/dL HDL-cholesterol 43 mg/dL LDL-cholesterol 73 mg/dL Triglycerides 135 mg/dL HDL: high-density lipoprotein; LDL: low-density lipoprotein Ibuprofen is prescribed for the acute treatment of this patient's symptoms. He is also put on chronic therapy to prevent the recurrence of future attacks. Which of the following drugs is 1st-line for chronic therapy of gout?