mTOR inhibitors — MCQs

10 questions

A 31-year-old female receives a kidney transplant for autosomal dominant polycystic kidney disease (ADPKD). Three weeks later, the patient experiences acute, T-cell mediated rejection of the allograft and is given sirolimus. Which of the following are side effects of this medication?

A patient with HCC and a long history of alcohol dependence and chronic hepatitis C has been using the mTOR inhibitor sirolimus 100 mg for cancer treatment. Her cancer has shown a partial response. She also has a history of hypertension and poorly controlled type 2 diabetes mellitus complicated by diabetic retinopathy. Current medications include enalapril and insulin. She asks her oncologist and hepatologist if she could try everolimus for its purported survival benefit in treating HCC. Based on clinical considerations, which of the following statements is most accurate?

An epidemiologist is evaluating the efficacy of Noxbinle in preventing HCC deaths at the population level. A clinical trial shows that over 5 years, the mortality rate from HCC was 25% in the control group and 15% in patients treated with Noxbinle 100 mg daily. Based on this data, how many patients need to be treated with Noxbinle 100 mg to prevent, on average, one death from HCC?

A 53-year-old man with hyperlipidemia comes to the physician for a follow-up examination. His home medications include acetaminophen and atorvastatin. Serum studies show elevated total cholesterol and triglyceride concentrations. A drug that activates the peroxisome proliferator-activated receptor alpha is added to his existing therapy. This patient is at highest risk for developing which of the following drug-related adverse effects?

A 14-year-old boy has undergone kidney transplantation due to stage V chronic kidney disease. A pre-transplantation serologic assessment showed that he is negative for past or present HIV infection, viral hepatitis, EBV, and CMV infection. He has a known allergy for macrolides. The patient has no complaints 1 day after transplantation. His vital signs include: blood pressure 120/70 mm Hg, heart rate 89/min, respiratory rate 17/min, and temperature 37.0°C (98.6°F). On physical examination, the patient appears to be pale, his lungs are clear on auscultation, heart sounds are normal, and his abdomen is non-tender on palpation. His creatinine is 0.65 mg/dL (57.5 µmol/L), GFR is 71.3 mL/min/1.73 m2, and urine output is 0.9 mL/kg/h. Which of the following drugs should be used in the immunosuppressive regimen in this patient?

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 50-year-old woman comes to the physician for the evaluation of excessive hair growth on her chin over the past 2 weeks. She also reports progressive enlargement of her gums. Three months ago, she underwent a liver transplantation due to Wilson disease. Following the procedure, the patient was started on transplant rejection prophylaxis. She has a history of poorly-controlled type 2 diabetes mellitus. Temperature is 37°C (98.6°F), pulse is 80/min, respirations are 22/min, and blood pressure is 150/80 mm Hg. Physical examination shows dark-pigmented, coarse hair on the chin, upper lip, and chest. The gingiva and the labial mucosa are swollen. There is a well-healed scar on her right lower abdomen. Which of the following drugs is the most likely cause of this patient's findings?

A 53-year old man presents for a well physical examination. He reports his diet is suboptimal, but otherwise reports a healthy lifestyle. He has no past medical history and only takes a multivitamin. He has a blood pressure of 116/74 mm Hg and a pulse of 76/min. On physical examination, he is in no acute distress, has no cardiac murmurs, and his lung sounds are clear to auscultation bilaterally. You order a lipid panel that returns as follows: LDL 203, HDL 37, TG 292. Of the following, which medication should be initiated?

A 53-year-old woman with hypertension and hyperlipidemia comes to the physician because of generalized reddening of her skin and itching for the past 2 weeks. Her symptoms occur every evening before bedtime and last for about 30 minutes. Three months ago, atorvastatin was stopped after she experienced progressively worsening neck and back pain. Statin therapy was reinitiated at lower doses 3 weeks ago but had to be stopped again after her musculoskeletal symptoms recurred. Her menses occur irregularly at 2–3 month intervals and last for 3–4 days. She has smoked one pack of cigarettes daily for the past 30 years. Her current medications include lisinopril and niacin. Her brother died of colonic adenocarcinoma, and her father died of small cell lung cancer. She is 169 cm (5 ft 6 in) tall and weighs 83 kg (183 lb); BMI is 29 kg/m2. Her vital signs are within normal limits. Physical examination shows no abnormalities. Serum lipid studies show: Total cholesterol 247 mg/dL HDL-cholesterol 39 mg/dL LDL-cholesterol 172 mg/dL Triglycerides 152 mg/dL Which of the following is the most appropriate next step in management?

Q10

A 24-year-old woman presents to the emergency department because she started experiencing dyspnea and urticaria after dinner. Her symptoms began approximately 15 minutes after eating a new type of shellfish that she has never had before. On physical exam her breathing is labored, and pulmonary auscultation reveals wheezing bilaterally. Given this presentation, she is immediately started on intramuscular epinephrine for treatment of her symptoms. If part of this patient's symptoms were related to the systemic release of certain complement components, which of the following is another function of the responsible component?

mTOR inhibitors US Medical PG Practice Questions and MCQs

Question 1: A 31-year-old female receives a kidney transplant for autosomal dominant polycystic kidney disease (ADPKD). Three weeks later, the patient experiences acute, T-cell mediated rejection of the allograft and is given sirolimus. Which of the following are side effects of this medication?

A. Nephrotoxicity, hypertension
B. Hyperlipidemia, thrombocytopenia (Correct Answer)
C. Nephrotoxicity, gingival hyperplasia
D. Pancreatitis
E. Cytokine release syndrome, hypersensitivity reaction

Explanation: ***Hyperlipidemia, thrombocytopenia*** - **Sirolimus** (rapamycin) is an **mTOR inhibitor** commonly used in transplant immunology, which frequently causes **hyperlipidemia** (elevated cholesterol and triglycerides) and **thrombocytopenia** (low platelet count). - Other common side effects include **myelosuppression** (leukopenia, anemia), **mouth ulcers**, and **impaired wound healing**. *Nephrotoxicity, hypertension* - **Nephrotoxicity** and **hypertension** are more characteristic side effects of **calcineurin inhibitors** like **tacrolimus** and **cyclosporine**, which are also used in transplant immunosuppression but have a different mechanism of action than sirolimus. - While sirolimus can indirectly affect kidney function, it is generally considered less nephrotoxic than calcineurin inhibitors. *Nephrotoxicity, gingival hyperplasia* - **Gingival hyperplasia** is a hallmark side effect of **cyclosporine**, a calcineurin inhibitor, along with **hirsutism** and **nephrotoxicity**. - Sirolimus does not typically cause gingival hyperplasia. *Pancreatitis* - While some immunosuppressants can rarely cause pancreatitis, it is not a common or characteristic side effect of **sirolimus**. - **Azathioprine** is more frequently associated with pancreatitis among immunosuppressive agents. *Cytokine release syndrome, hypersensitivity reaction* - **Cytokine release syndrome** and acute **hypersensitivity reactions** are more often associated with **monoclonal antibodies** (e.g., **basiliximab**, **daclizumab**) used for induction therapy or treatment of acute rejection, particularly within hours or days of administration. - Sirolimus is less likely to cause these immediate severe reactions.

Question 2: A patient with HCC and a long history of alcohol dependence and chronic hepatitis C has been using the mTOR inhibitor sirolimus 100 mg for cancer treatment. Her cancer has shown a partial response. She also has a history of hypertension and poorly controlled type 2 diabetes mellitus complicated by diabetic retinopathy. Current medications include enalapril and insulin. She asks her oncologist and hepatologist if she could try everolimus for its purported survival benefit in treating HCC. Based on clinical considerations, which of the following statements is most accurate?

A. The patient should start everolimus 50 mg because of the survival benefit relative to sirolimus 100 mg
B. The patient is not a good candidate for everolimus due to her history of hypertension
C. The patient should start everolimus 100 mg because of the survival benefit relative to sirolimus 100 mg
D. The patient should start everolimus 50 mg because of her history of alcohol use disorder and hepatitis C
E. The patient is not a good candidate for everolimus due to her history of diabetes (Correct Answer)

Explanation: ***The patient is not a good candidate for Noxbinle due to her history of diabetes*** - The current medication is sirolimus, an **mTOR inhibitor** and its successor everolimus, also an mTOR inhibitor, is not beneficial for this patient due to her **poorly controlled type 2 diabetes mellitus**. - mTOR inhibitors, including everolimus, are known to **worsen hyperglycemia** and **accelerate the progression of diabetes**, making it contraindicated in patients with already complicated diabetes. *The patient should start everolimus 50 mg because of the survival benefit relative to sirolimus 100 mg* - There is **no established evidence** that everolimus at any dose offers a superior survival benefit compared to sirolimus in HCC, particularly after a partial response to sirolimus. - **Switching mTOR inhibitors** without a compelling clinical reason, especially with existing comorbidities, is not standard practice. *The patient is not a good candidate for everolimus due to her history of hypertension* - While mTOR inhibitors can contribute to **hypertension**, this patient is already on **enalapril** for her existing hypertension. - Her **poorly controlled diabetes** presents a more direct and severe contraindication due to the metabolic side effects of everolimus. *The patient should start everolimus 100 mg because of the survival benefit relative to sirolimus 100 mg* - No clinical data supports a **superior survival benefit** of everolimus 100 mg over sirolimus 100 mg in HCC. - Given the patient's existing **poorly controlled diabetes**, increasing the dose of an mTOR inhibitor or switching to an equivalent dose of another would heighten the risk of severe metabolic complications. *The patient should start everolimus 50 mg because of her history of alcohol use disorder and hepatitis C* - The patient's history of alcohol dependence and chronic hepatitis C are **risk factors for HCC** but do not directly contraindicate a specific dose of everolimus more than her diabetes. - While liver impairment due to these conditions might influence dosing of various medications, the **primary concern for everolimus** in this case remains the uncontrolled diabetes.

Question 3: An epidemiologist is evaluating the efficacy of Noxbinle in preventing HCC deaths at the population level. A clinical trial shows that over 5 years, the mortality rate from HCC was 25% in the control group and 15% in patients treated with Noxbinle 100 mg daily. Based on this data, how many patients need to be treated with Noxbinle 100 mg to prevent, on average, one death from HCC?

A. 20
B. 73
C. 10 (Correct Answer)
D. 50
E. 100

Explanation: ***10*** - The **number needed to treat (NNT)** is calculated by first finding the **absolute risk reduction (ARR)**. - **ARR** = Risk in control group - Risk in treatment group = 25% - 15% = **10%** (or 0.10). - **NNT = 1 / ARR** = 1 / 0.10 = **10 patients**. - This means that **10 patients must be treated with Noxbinle to prevent one death from HCC** over 5 years. *20* - This would result from an ARR of 5% (1/0.05 = 20), which is not supported by the data. - May arise from miscalculating the risk difference or incorrectly halving the actual ARR. *73* - This value does not correspond to any standard calculation of NNT from the given mortality rates. - May result from confusion with other epidemiological measures or calculation error. *50* - This would correspond to an ARR of 2% (1/0.02 = 50), which significantly underestimates the actual risk reduction. - Could result from incorrectly calculating the difference as a proportion rather than absolute percentage points. *100* - This would correspond to an ARR of 1% (1/0.01 = 100), grossly underestimating the treatment benefit. - May result from confusing ARR with relative risk reduction or other calculation errors.

Question 4: A 53-year-old man with hyperlipidemia comes to the physician for a follow-up examination. His home medications include acetaminophen and atorvastatin. Serum studies show elevated total cholesterol and triglyceride concentrations. A drug that activates the peroxisome proliferator-activated receptor alpha is added to his existing therapy. This patient is at highest risk for developing which of the following drug-related adverse effects?

A. Reddish-brown discoloration of urine (Correct Answer)
B. Bleeding from minor trauma
C. Waxing and waning confusion
D. Acutely swollen and painful joint
E. Pruritus and flushing of the skin

Explanation: ***Reddish-brown discoloration of urine*** - This patient is likely being treated with a **fibrate**, a PPAR-alpha agonist, in addition to **atorvastatin** due to persistently elevated triglycerides. - The combination of a fibrate and a statin increases the risk of **rhabdomyolysis**, which can cause **myoglobinuria**, leading to reddish-brown urine and potential **acute kidney injury**. *Bleeding from minor trauma* - This adverse effect is more characteristic of **anticoagulants** (e.g., warfarin, direct oral anticoagulants) or **antiplatelet agents** (e.g., aspirin, clopidogrel). - Fibrates and statins do not typically cause significant bleeding diathesis. *Waxing and waning confusion* - This can be a symptom of various conditions, including **hepatic encephalopathy**, severe electrolyte imbalances, or delirium; it is not a common adverse effect of fibrates or statins. - While statins can rarely cause cognitive side effects, **confusion** of this nature is not a hallmark. *Acutely swollen and painful joint* - This symptom strongly suggests an acute **arthritic flare**, particularly **gout**, caused by hyperuricemia. - While some medications can induce gout (e.g., diuretics), neither fibrates nor statins are commonly associated with this adverse effect. *Pruritus and flushing of the skin* - These are characteristic side effects of **niacin (nicotinic acid)**, another lipid-lowering agent. - Niacin causes prostaglandin-mediated vasodilation, leading to intense **flushing and itching**, which can be severe enough to cause medication non-adherence.

Question 5: A 14-year-old boy has undergone kidney transplantation due to stage V chronic kidney disease. A pre-transplantation serologic assessment showed that he is negative for past or present HIV infection, viral hepatitis, EBV, and CMV infection. He has a known allergy for macrolides. The patient has no complaints 1 day after transplantation. His vital signs include: blood pressure 120/70 mm Hg, heart rate 89/min, respiratory rate 17/min, and temperature 37.0°C (98.6°F). On physical examination, the patient appears to be pale, his lungs are clear on auscultation, heart sounds are normal, and his abdomen is non-tender on palpation. His creatinine is 0.65 mg/dL (57.5 µmol/L), GFR is 71.3 mL/min/1.73 m2, and urine output is 0.9 mL/kg/h. Which of the following drugs should be used in the immunosuppressive regimen in this patient?

A. Belatacept
B. Sirolimus
C. Omalizumab
D. Daclizumab
E. Basiliximab (Correct Answer)

Explanation: **Basiliximab** - **Basiliximab** is a **monoclonal antibody** that targets the **IL-2 receptor (CD25)** on activated T cells, preventing their proliferation and inducing immunosuppression. - It is commonly used as **induction therapy** in kidney transplant recipients due to its good safety profile, especially in pediatric patients, without the nephrotoxicity associated with calcineurin inhibitors, minimizing acute rejection risks immediately post-transplant. *Belatacept* - **Belatacept** works by co-stimulation blockade, binding to **CD80 and CD86** on antigen-presenting cells to prevent T-cell activation. - It is typically reserved for patients who cannot tolerate calcineurin inhibitors due to **nephrotoxicity** or require a steroid-sparing regimen, which is not indicated as an immediate need in this patient. *Sirolimus* - **Sirolimus** is an **mTOR inhibitor** that works by blocking T-cell proliferation and B-cell differentiation. - It is associated with several side effects, including **delayed wound healing**, **thrombocytopenia**, and **hyperlipidemia**, which are undesirable in the immediate post-transplant period, especially in a growing adolescent. *Omalizumab* - **Omalizumab** is an **anti-IgE monoclonal antibody** primarily used for allergic asthma and chronic spontaneous urticaria. - It has no role in **immunosuppression for organ transplantation** as its mechanism of action is unrelated to preventing graft rejection. *Daclizumab* - **Daclizumab** is another **monoclonal antibody** that also targets the **IL-2 receptor (CD25)**, similar to basiliximab. - However, daclizumab has been **withdrawn from the market** due to serious adverse effects including severe liver injury and autoimmune encephalitis, making it unavailable for clinical use in transplantation.

Question 6: 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. Mycophenolate mofetil
B. Azathioprine
C. Tacrolimus
D. Cyclosporine (Correct Answer)
E. Prednisolone

Explanation: ***Cyclosporine*** - The patient's symptoms of **gingival hyperplasia**, **hypertension**, and **hyperlipidemia** are classic side effects associated with cyclosporine. - Cyclosporine is a calcineurin inhibitor that **decreases T-cell activation** by inhibiting IL-2 transcription, matching the drug description. *Mycophenolate mofetil* - Mycophenolate mofetil is an **antiproliferative agent** that inhibits purine synthesis, primarily affecting lymphocytes. - Its common side effects are mainly **hematologic** (leukopenia, anemia) and **gastrointestinal** (diarrhea, nausea), not gingival hyperplasia or hypertension. *Azathioprine* - Azathioprine is a **purine analog** that impairs DNA synthesis and inhibits lymphocyte proliferation. - Key side effects include **myelosuppression** (leukopenia, thrombocytopenia) and **hepatotoxicity**, which are not present here. *Tacrolimus* - Tacrolimus is also a **calcineurin inhibitor** that inhibits IL-2 transcription, similar to cyclosporine. - While it can cause **hypertension** and **hyperlipidemia**, it is less commonly associated with **gingival hyperplasia** than cyclosporine. *Prednisolone* - Prednisolone is a **corticosteroid** used for immunosuppression, acting broadly on the immune system. - Common side effects include **hyperglycemia**, **osteoporosis**, and **cataracts**, not specific gingival overgrowth.

Question 7: A 50-year-old woman comes to the physician for the evaluation of excessive hair growth on her chin over the past 2 weeks. She also reports progressive enlargement of her gums. Three months ago, she underwent a liver transplantation due to Wilson disease. Following the procedure, the patient was started on transplant rejection prophylaxis. She has a history of poorly-controlled type 2 diabetes mellitus. Temperature is 37°C (98.6°F), pulse is 80/min, respirations are 22/min, and blood pressure is 150/80 mm Hg. Physical examination shows dark-pigmented, coarse hair on the chin, upper lip, and chest. The gingiva and the labial mucosa are swollen. There is a well-healed scar on her right lower abdomen. Which of the following drugs is the most likely cause of this patient's findings?

A. Daclizumab
B. Cyclosporine (Correct Answer)
C. Sirolimus
D. Methotrexate
E. Tacrolimus

Explanation: **Cyclosporine** * This patient's **combination of hirsutism** (excessive hair growth) **and gingival hyperplasia** (gum enlargement) is the classic presentation of cyclosporine toxicity, an immunosuppressant commonly used for transplant rejection prophylaxis. * Cyclosporine is a **calcineurin inhibitor** that prevents T-cell activation and is highly effective in preventing graft rejection. * The **simultaneous presence of both hirsutism and prominent gingival hyperplasia** is particularly characteristic of cyclosporine. *Daclizumab* * **Daclizumab** is a **monoclonal antibody** targeting the IL-2 receptor, which was previously used for transplant prophylaxis but has been discontinued for this indication. * It is not associated with hirsutism or gingival hyperplasia. *Sirolimus* * **Sirolimus** is an **mTOR inhibitor** used as an immunosuppressant, known for side effects like hyperlipidemia, myelosuppression, and delayed wound healing. * It does **not** typically cause hirsutism or gingival hyperplasia. *Methotrexate* * **Methotrexate** is an **antimetabolite** and immunosuppressant commonly used in autoimmune diseases and cancer, with side effects including bone marrow suppression, mucositis, and liver toxicity. * Hirsutism and gingival hyperplasia are **not** characteristic side effects of methotrexate. *Tacrolimus* * **Tacrolimus** is another **calcineurin inhibitor**, similar to cyclosporine, but with a different side effect profile. While tacrolimus can cause hirsutism, **gingival hyperplasia is significantly less common** with tacrolimus compared to cyclosporine. * The **presence of prominent gingival hyperplasia alongside hirsutism strongly favors cyclosporine** over tacrolimus. * Tacrolimus is more commonly associated with **neurotoxicity** (e.g., tremor) and **nephrotoxicity**.

Question 8: A 53-year old man presents for a well physical examination. He reports his diet is suboptimal, but otherwise reports a healthy lifestyle. He has no past medical history and only takes a multivitamin. He has a blood pressure of 116/74 mm Hg and a pulse of 76/min. On physical examination, he is in no acute distress, has no cardiac murmurs, and his lung sounds are clear to auscultation bilaterally. You order a lipid panel that returns as follows: LDL 203, HDL 37, TG 292. Of the following, which medication should be initiated?

A. Ezetimibe 10 mg daily
B. Colesevelam 3.75 grams daily
C. Atorvastatin 40 mg daily (Correct Answer)
D. Fenofibrate 145 mg daily
E. Simvastatin 10 mg daily

Explanation: ***Atorvastatin 40 mg*** - This patient has a **very high LDL level of 203 mg/dL** and is over 40 years old, placing him in a high-risk group that warrants initiation of a **high-intensity statin** for primary prevention of cardiovascular disease. - **Atorvastatin 40 mg** is a high-intensity statin known to reduce LDL cholesterol by 50% or more, which is appropriate for this patient's elevated risk. *Ezetimibe 10 mg daily* - **Ezetimibe** works by inhibiting cholesterol absorption in the small intestine and is typically used as an add-on therapy for patients who do not achieve their LDL goals with statins alone, or for those who are statin-intolerant. - It is not a first-line monotherapy for a patient with such significantly elevated LDL cholesterol. *Colesevelam 3.75 grams daily* - **Colesevelam** is a bile acid sequestrant that lowers LDL by increasing its fecal excretion; however, it has a more modest LDL-lowering effect compared to statins and can sometimes increase triglycerides. - It is not the most effective or appropriate first-line agent, especially given the patient's existing elevated triglyceride levels. *Fenofibrate 145 mg daily* - **Fenofibrate** is primarily used to lower **triglycerides** and can mildly raise HDL, but it has minimal effect on LDL cholesterol. - While the patient has elevated triglycerides, his primary and most significant lipid abnormality requiring immediate intervention for cardiovascular risk reduction is his severely elevated LDL. *Simvastatin 10 mg daily* - **Simvastatin 10 mg** is a **low-intensity statin** dose (typical range: 10-20 mg), which is not sufficient for a patient with an LDL of 203 mg/dL and high cardiovascular risk. - Guidelines recommend a **high-intensity statin** like atorvastatin 40-80 mg or rosuvastatin 20-40 mg for such elevated LDL levels.

Question 9: A 53-year-old woman with hypertension and hyperlipidemia comes to the physician because of generalized reddening of her skin and itching for the past 2 weeks. Her symptoms occur every evening before bedtime and last for about 30 minutes. Three months ago, atorvastatin was stopped after she experienced progressively worsening neck and back pain. Statin therapy was reinitiated at lower doses 3 weeks ago but had to be stopped again after her musculoskeletal symptoms recurred. Her menses occur irregularly at 2–3 month intervals and last for 3–4 days. She has smoked one pack of cigarettes daily for the past 30 years. Her current medications include lisinopril and niacin. Her brother died of colonic adenocarcinoma, and her father died of small cell lung cancer. She is 169 cm (5 ft 6 in) tall and weighs 83 kg (183 lb); BMI is 29 kg/m2. Her vital signs are within normal limits. Physical examination shows no abnormalities. Serum lipid studies show: Total cholesterol 247 mg/dL HDL-cholesterol 39 mg/dL LDL-cholesterol 172 mg/dL Triglycerides 152 mg/dL Which of the following is the most appropriate next step in management?

A. Switch lisinopril to hydrochlorothiazide
B. Measure urine hydroxyindoleacetic acid levels
C. Measure urine metanephrine levels
D. Administer ibuprofen
E. Switch niacin to fenofibrate (Correct Answer)

Explanation: ***Switch niacin to fenofibrate*** - The patient is experiencing **niacin-induced flushing** (generalized reddening and itching every evening before bedtime), which is a common side effect of nicotinic acid due to prostaglandin-mediated vasodilation. - Given her **statin intolerance** (tried twice with recurrent myalgias) and problematic side effects from niacin, switching to an alternative lipid-lowering agent is reasonable for long-term management. - **Fenofibrate** (a fibrate) primarily lowers triglycerides and can modestly reduce LDL while raising HDL, providing an alternative lipid-lowering approach without the flushing side effects of niacin. - While her triglycerides are only borderline elevated (152 mg/dL), fenofibrate can still contribute to overall lipid management in this statin-intolerant patient. *Administer ibuprofen* - **Ibuprofen or aspirin pre-treatment** (taken 30 minutes before niacin) is actually the **first-line strategy** to prevent niacin-induced flushing by inhibiting prostaglandin synthesis. - This approach allows continuation of niacin therapy while managing the side effect, which is clinically valuable given her statin intolerance. - However, in the context of this question, switching to an alternative agent (fenofibrate) may be considered more definitive management rather than ongoing symptomatic prophylaxis, especially if the patient desires to avoid the flushing entirely. *Switch lisinopril to hydrochlorothiazide* - There is no indication that **lisinopril** (an ACE inhibitor) is causing problems or is inappropriate for her hypertension. - Her vital signs are within normal limits, and switching antihypertensive therapy is not indicated when the presenting issue is clearly related to her lipid-lowering medication. *Measure urine hydroxyindoleacetic acid levels* - Measuring **urine 5-HIAA** is used to diagnose **carcinoid syndrome**, which can cause episodic flushing. - However, the temporal relationship between niacin initiation (3 weeks ago) and symptom onset (2 weeks ago), plus the predictable evening timing before bedtime, makes niacin-induced flushing the obvious diagnosis. *Measure urine metanephrine levels* - This test diagnoses **pheochromocytoma**, which causes episodic hypertension and flushing. - The patient has normal vital signs and a clear medication-related cause for her symptoms, making pheochromocytoma investigation unnecessary.

Question 10: A 24-year-old woman presents to the emergency department because she started experiencing dyspnea and urticaria after dinner. Her symptoms began approximately 15 minutes after eating a new type of shellfish that she has never had before. On physical exam her breathing is labored, and pulmonary auscultation reveals wheezing bilaterally. Given this presentation, she is immediately started on intramuscular epinephrine for treatment of her symptoms. If part of this patient's symptoms were related to the systemic release of certain complement components, which of the following is another function of the responsible component?

A. Chemotaxis (Correct Answer)
B. Direct cytolysis
C. Inhibition of kallikrein activation
D. Clearance of immune complexes
E. Opsonization of pathogens

Explanation: **Chemotaxis** - The patient's symptoms are consistent with **anaphylaxis**, an IgE-mediated hypersensitivity reaction that causes mast cell degranulation. - During anaphylaxis, mast cells release mediators that can activate the **complement system**, producing anaphylatoxins like C3a and C5a. **C5a** is a potent **chemotactic factor** for neutrophils and macrophages, attracting them to the site of inflammation. *Direct cytolysis* - **Direct cytolysis** is primarily mediated by the **membrane attack complex (MAC)**, formed by C5b-C9. - While complement activation occurs in anaphylaxis, the immediate severe symptoms like urticaria and bronchospasm are predominantly due to mast cell degranulation and the release of histamine and other mediators, not direct cell lysis by MAC which occurs in later stages or different contexts. *Inhibition of kallikrein activation* - **Kallikrein activation** is inhibited by **C1 esterase inhibitor (C1-INH)**. - A deficiency in C1-INH leads to conditions like **hereditary angioedema**, which is distinct from the type I hypersensitivity reaction (anaphylaxis) described in the patient. *Clearance of immune complexes* - **Clearance of immune complexes** is a function primarily associated with **C3b** binding to immune complexes, allowing their uptake by phagocytes or transport to the liver and spleen. - While immune complexes are involved in other types of hypersensitivity reactions, they are not the primary mechanism or a direct complement component involved in the acute allergic reaction due to shellfish. *Opsonization of pathogens* - **Opsonization** is the process by which pathogens are tagged for phagocytosis, chiefly performed by **C3b** and antibodies. - While complement plays a role in host defense, opsonization is not the function of the complement components (C3a, C5a) primarily responsible for the anaphylactoid reactions seen in this patient's presentation.

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