A 62-year-old male presents to his primary care physician complaining of a chronic cough. He reports a six-month history of progressively worsening cough and occasional hemoptysis. He has lost ten pounds over the same time frame. His medical history is notable for hypertension, hyperlipidemia, and diabetes mellitus. He has a 50-pack-year smoking history. A chest radiograph reveals a coin-like central cavitary lesion. Tissue biopsy demonstrates findings consistent with squamous cell carcinoma. The patient is referred to a pulmonologist who starts the patient on a chemotherapeutic drug. However, after several weeks on the drug, the patient develops sensorineural hearing loss. Which of the following mechanisms of action is consistent with the most likely medication prescribed in this case?
Q32
A 64-year-old man presents to his primary care physician for a fall. The patient states that he has felt abnormally clumsy lately and has noticed himself tripping and bumping into things. He states he otherwise is healthy but admits to having unprotected sex with multiple people recently. His temperature is 99.5°F (37.5°C), blood pressure is 127/68 mm Hg, pulse is 100/min, respiratory rate is 24/min, and oxygen saturation is 98% on room air. Laboratory values are ordered as seen below.
Hemoglobin: 9 g/dL
Hematocrit: 30%
Mean corpuscular volume: 110 fL
Leukocyte count: 6,500/mm^3 with normal differential
Platelet count: 197,000/mm^3
AST: 15 U/L
ALT: 22 U/L
GGT: 10 U/L
Physical exam is notable for a broad-based and unstable gait. Which of the following conditions is the most likely etiology of this patient's presentation?
Q33
A 45-year-old woman with a history of alcoholic hepatitis returns to clinic for follow-up after being diagnosed with rheumatoid arthritis and started on NSAIDs. She complains of continued joint effusions and increasing morning stiffness. Given this patient's presentation and history, which of the following drugs presents the greatest risk when started for the management of her condition?
Q34
A mother brings her 8-month-old child to your pediatric clinic with concerns of a rash. Physical exam reveals an erythematous, weeping rash involving bilateral cheeks and scalp. You prescribe a topical agent that is considered the first-line pharmacological treatment for this condition. What is a common concern that the mother should be alerted to regarding long-term use of this topical agent?
Q35
A 33-year-old woman comes to the physician because of constipation, abdominal pain, and decreased appetite for the past 2 months. She started a new diet and has been exercising 2 hours daily for several months in order to lose weight. She has a history of hypertension and hypothyroidism. She does not smoke or drink alcohol. Current medications include hydrochlorothiazide, a multivitamin, and levothyroxine. She recently started taking over-the-counter supplements with each meal. Her temperature is 36.2°C (97.2°F), pulse is 92/min, and blood pressure is 102/78 mm Hg. Examination shows dry mucous membranes. Cardiopulmonary examination shows no abnormalities. Her abdomen is soft; bowel sounds are decreased. Serum studies show:
Calcium 12.8 mg/dL
Phosphorus 4.6 mg/dL
Bicarbonate 22 mEq/L
Albumin 4 g/dL
PTH 180 pg/mL
TSH 9 μU/mL
Free T4 5 μg/dL
Which of the following is the most likely underlying cause of this patient's symptoms?
Q36
A 58-year-old female presents with a two-month history of intermittent non-bloody diarrhea. She reports that she has been following a raw food diet for six months to help her lose weight. The patient’s medical history is significant for anxiety, treated with fluvoxamine, and osteopenia. She reports her mother has lactose intolerance and has recently been diagnosed with osteoporosis. The patient denies any tobacco or alcohol use. When asked about recent travel, she reports she returned three months ago from a mission trip in Uganda. The patient’s temperature is 99°F (37.2°C), blood pressure is 130/78 mmHg, pulse is 70/min, and respirations are 14/min with an oxygen saturation of 98% O2 on room air. On physical exam, a new-onset systolic ejection murmur is noted and is heard loudest at the left second intercostal space. Which of the following may develop in this patient?
Q37
A 25-year-old woman first presented to your clinic due to morning stiffness, symmetrical arthralgia in her wrist joints, and fatigue. She had a blood pressure of 132/74 mm Hg and heart rate of 84/min. Physical examination revealed tenderness to palpation of both wrists but full range of motion. Anti-citrullinated protein antibodies were positive and ESR was above normal ranges. She was started on methotrexate therapy. She returns for follow up 2 months later and is found to have megaloblastic anemia. What is the mechanism of action of methotrexate?
Q38
A 2-year-old boy is brought in by his parents to his pediatrician. The boy was born by spontaneous vaginal delivery at 39 weeks and 5 days after a normal pregnancy. The boy has received all age-appropriate vaccinations as of his last visit at 18 months of age. Of note, the boy has confirmed sickle cell disease and the only medication he takes is penicillin prophylaxis. The parents state that they plan on enrolling their son in a daycare, which requires documentation of up-to-date vaccinations. The pediatrician states that their son needs an additional vaccination at this visit, which is a polysaccharide vaccine that is not conjugated to protein. Which of the following matches this description?
Q39
A 57-year-old man presents to the emergency department with fatigue. He states that his symptoms started yesterday and have been worsening steadily. The patient endorses a recent weight loss of 7 pounds this past week and states that he feels diffusely itchy. The patient has a past medical history of alcohol abuse, obesity, asthma, and IV drug use. His current medications include metformin, atorvastatin, albuterol, and fluticasone. In addition, the patient admits to smoking and drinking more than usual lately due to the stress he has experienced. His temperature is 98.7°F (37.1°C), blood pressure is 130/75 mmHg, pulse is 90/min, respirations are 15/min, and oxygen saturation is 98% on room air. Physical exam is notable for an ill-appearing man. The patient's skin appears yellow. Abdominal exam is notable for right upper quadrant tenderness. Cardiac and pulmonary exams are within normal limits. Laboratory values are ordered as seen below:
Hemoglobin: 14 g/dL
Hematocrit: 42%
Leukocyte count: 5,500 cells/mm^3 with normal differential
Platelet count: 70,000/mm^3
Partial thromboplastin time: 92 seconds
Prothrombin time: 42 seconds
AST: 1110 U/L
ALT: 990 U/L
Which of the following is most likely to be found in this patient's history?
Q40
A 63-year-old man with inoperable esophageal carcinoma undergoes palliative chemoradiotherapy. Four hours after his first infusion of carboplatin and paclitaxel, he develops nausea and 3 episodes of vomiting and dry heaving. This adverse reaction is caused by stimulation of a brain region on the floor of the fourth ventricle. Chemotherapeutic drugs are able to stimulate this region because of the absence of a cell junction that is composed of which of the following proteins?
Antimicrobials US Medical PG Practice Questions and MCQs
Question 31: A 62-year-old male presents to his primary care physician complaining of a chronic cough. He reports a six-month history of progressively worsening cough and occasional hemoptysis. He has lost ten pounds over the same time frame. His medical history is notable for hypertension, hyperlipidemia, and diabetes mellitus. He has a 50-pack-year smoking history. A chest radiograph reveals a coin-like central cavitary lesion. Tissue biopsy demonstrates findings consistent with squamous cell carcinoma. The patient is referred to a pulmonologist who starts the patient on a chemotherapeutic drug. However, after several weeks on the drug, the patient develops sensorineural hearing loss. Which of the following mechanisms of action is consistent with the most likely medication prescribed in this case?
A. Folate analog
B. Microtubule inhibitor
C. Platinum-based DNA crosslinker (Correct Answer)
D. DNA alkylating agent
E. DNA intercalating agent
Explanation: ***Platinum-based DNA crosslinker***
- The patient's presentation with a **central cavitary lesion** and **squamous cell carcinoma** of the lung, along with a significant smoking history, strongly suggests a **chemotherapeutic regimen** that commonly includes platinum-based drugs like **cisplatin** or **carboplatin**.
- **Sensorineural hearing loss** (**ototoxicity**) is a well-known and significant side effect of platinum-based antineoplastic agents, which create **DNA crosslinks** to inhibit replication and transcription.
*Folate analog*
- **Folate analogs** like **methotrexate** inhibit **dihydrofolate reductase**, interfering with DNA synthesis, and are used in various cancers.
- While they can cause myelosuppression and mucositis, **ototoxicity** is **not a characteristic side effect** of this class of drugs.
*Microtubule inhibitor*
- **Microtubule inhibitors** (**e.g., taxanes, vinca alkaloids**) interfere with microtubule function, essential for cell division.
- They are associated with **neuropathy** and myelosuppression, but **sensorineural hearing loss** is **not a prominent adverse effect**.
*DNA alkylating agent*
- **DNA alkylating agents** form covalent bonds with DNA, leading to DNA damage and cell death.
- While they cause a range of toxicities, **significant ototoxicity** leading to sensorineural hearing loss is **not typically a hallmark** of this group compared to platinum-based drugs.
*DNA intercalating agent*
- **DNA intercalating agents** insert themselves between DNA base pairs, unwinding the helix and inhibiting replication and transcription.
- Drugs like **doxorubicin** (an anthracycline) can cause cardiotoxicity and myelosuppression, but **ototoxicity** is **not a primary adverse effect**.
Question 32: A 64-year-old man presents to his primary care physician for a fall. The patient states that he has felt abnormally clumsy lately and has noticed himself tripping and bumping into things. He states he otherwise is healthy but admits to having unprotected sex with multiple people recently. His temperature is 99.5°F (37.5°C), blood pressure is 127/68 mm Hg, pulse is 100/min, respiratory rate is 24/min, and oxygen saturation is 98% on room air. Laboratory values are ordered as seen below.
Hemoglobin: 9 g/dL
Hematocrit: 30%
Mean corpuscular volume: 110 fL
Leukocyte count: 6,500/mm^3 with normal differential
Platelet count: 197,000/mm^3
AST: 15 U/L
ALT: 22 U/L
GGT: 10 U/L
Physical exam is notable for a broad-based and unstable gait. Which of the following conditions is the most likely etiology of this patient's presentation?
A. Tertiary syphilis
B. Vegetarian diet
C. Colon cancer
D. Chronic alcoholism
E. Chronic gastritis (Correct Answer)
Explanation: ***Chronic gastritis***
- Chronic gastritis can lead to **vitamin B12 deficiency** due to impaired **intrinsic factor** production, resulting in **macrocytic anemia** (evidenced by **Hb 9 g/dL**, **MCV 110 fL**).
- Vitamin B12 deficiency can cause neurological symptoms like **ataxia** and **clumsiness (broad-based, unstable gait)** from **subacute combined degeneration** of the spinal cord.
*Tertiary syphilis*
- Tertiary syphilis can cause **tabes dorsalis**, characterized by ataxia and sensory deficits, which could explain the gait disturbance.
- However, the lab findings of **macrocytic anemia** (high MCV) are more indicative of **vitamin B12 deficiency**, which is not a direct consequence of syphilis.
*Vegetarian diet*
- A strict vegetarian diet can lead to **vitamin B12 deficiency** because B12 is primarily found in animal products.
- While it can cause macrocytic anemia and neurological symptoms, the patient's history of **unprotected sex** and lack of dietary information makes other etiologies more likely.
*Colon cancer*
- Colon cancer typically causes **microcytic anemia** due to chronic blood loss, not **macrocytic anemia**.
- While it can cause fatigue, it does not directly explain the neurological symptoms of clumsiness and unstable gait in this manner.
*Chronic alcoholism*
- Chronic alcoholism can lead to **macrocytic anemia** due to **folate deficiency** or direct toxic effects on the bone marrow.
- While it can cause neurological deficits (e.g., Wernicke-Korsakoff syndrome, alcoholic polyneuropathy), the provided liver enzymes (AST 15 U/L, ALT 22 U/L, GGT 10 U/L) are **normal**, making severe chronic alcoholism less likely to be the primary cause of his symptoms and lab findings.
Question 33: A 45-year-old woman with a history of alcoholic hepatitis returns to clinic for follow-up after being diagnosed with rheumatoid arthritis and started on NSAIDs. She complains of continued joint effusions and increasing morning stiffness. Given this patient's presentation and history, which of the following drugs presents the greatest risk when started for the management of her condition?
A. Etanercept
B. Corticosteroids
C. Cyclosporine
D. Hydroxychloroquine
E. Methotrexate (Correct Answer)
Explanation: ***Methotrexate***
- **Methotrexate** is a cornerstone of rheumatoid arthritis treatment but is **hepatotoxic** and contraindicated in patients with significant liver disease, like this patient with a history of **alcoholic hepatitis**.
- Its use in this patient would significantly **exacerbate liver damage** and could lead to severe hepatic complications.
*Etanercept*
- **Etanercept** is a TNF-alpha inhibitor and generally well-tolerated, but carries risks of **infections** and **demyelinating disorders**, not primarily liver toxicity.
- While it can sometimes impact liver enzymes, it is not a direct contraindication in stable, non-active liver disease.
*Corticosteroids*
- **Corticosteroids** can cause side effects such as **osteoporosis**, **hyperglycemia**, and **infections**, but they are often used cautiously for short-term control in patients with liver disease.
- They are not primarily hepatotoxic to the extent of methotrexate.
*Cyclosporine*
- **Cyclosporine** is an immunosuppressant that can be **nephrotoxic** and may cause **hypertension** or **gingival hyperplasia**.
- While it has some potential for hepatotoxicity, it is generally considered less risky than methotrexate in patients with a history of alcoholic liver disease.
*Hydroxychloroquine*
- **Hydroxychloroquine** is a relatively safe DMARD, with primary side effects including **retinal toxicity** and **gastrointestinal upset**.
- It has a low risk of significant hepatotoxicity and is generally considered safe in patients with liver disease.
Question 34: A mother brings her 8-month-old child to your pediatric clinic with concerns of a rash. Physical exam reveals an erythematous, weeping rash involving bilateral cheeks and scalp. You prescribe a topical agent that is considered the first-line pharmacological treatment for this condition. What is a common concern that the mother should be alerted to regarding long-term use of this topical agent?
A. Paresthesia
B. Hypoglycemia
C. Hyperpigmentation
D. Increased risk of melanoma
E. Skin atrophy (Correct Answer)
Explanation: ***Skin atrophy***
- The rash described (erythematous, weeping, involving cheeks and scalp in an 8-month-old) is characteristic of **atopic dermatitis** (eczema). First-line pharmacological treatment for atopic dermatitis involves **topical corticosteroids**.
- **Long-term use of topical corticosteroids**, especially on delicate skin like that of an infant's face, can lead to **skin atrophy**, characterized by thinning of the skin, telangiectasias, and striae.
*Paresthesia*
- This symptom, often described as tingling or numbness, is not a typical side effect associated with the **long-term use of topical corticosteroids**.
- Paresthesia is more commonly linked to nerve damage, vitamin deficiencies, or certain systemic medications.
*Hypoglycemia*
- **Systemic corticosteroids** can cause hyperglycemia, but topical corticosteroids generally have minimal systemic absorption unless very potent, applied over large areas, or under occlusion.
- **Topical corticosteroids** are not associated with hypoglycemia.
*Hyperpigmentation*
- While skin changes can occur with chronic inflammation, topical corticosteroids are generally associated with **hypopigmentation** (lightening of the skin) rather than hyperpigmentation, particularly with prolonged use or on darker skin types.
- **Post-inflammatory hyperpigmentation** can occur after eczema resolves, but it's not a direct side effect of the topical steroid itself.
*Increased risk of melanoma*
- There is **no established link** between the long-term use of topical corticosteroids and an increased risk of developing melanoma.
- Melanoma is a type of skin cancer primarily associated with UV radiation exposure and genetic factors.
Question 35: A 33-year-old woman comes to the physician because of constipation, abdominal pain, and decreased appetite for the past 2 months. She started a new diet and has been exercising 2 hours daily for several months in order to lose weight. She has a history of hypertension and hypothyroidism. She does not smoke or drink alcohol. Current medications include hydrochlorothiazide, a multivitamin, and levothyroxine. She recently started taking over-the-counter supplements with each meal. Her temperature is 36.2°C (97.2°F), pulse is 92/min, and blood pressure is 102/78 mm Hg. Examination shows dry mucous membranes. Cardiopulmonary examination shows no abnormalities. Her abdomen is soft; bowel sounds are decreased. Serum studies show:
Calcium 12.8 mg/dL
Phosphorus 4.6 mg/dL
Bicarbonate 22 mEq/L
Albumin 4 g/dL
PTH 180 pg/mL
TSH 9 μU/mL
Free T4 5 μg/dL
Which of the following is the most likely underlying cause of this patient's symptoms?
A. Primary hypothyroidism
B. Excess calcium carbonate intake
C. Primary hyperparathyroidism
D. Vitamin D toxicity (Correct Answer)
E. Vitamin A toxicity
Explanation: ***Vitamin D toxicity***
- The patient's **elevated calcium** (12.8 mg/dL) and **normal to mildly elevated phosphorus** (4.6 mg/dL) suggest hypercalcemia with increased intestinal absorption.
- The patient's recent intake of "over-the-counter supplements with each meal" suggests potential excessive vitamin D intake, especially given her focus on weight loss and exercise, which may have prompted supplementation.
- **Note:** The PTH value of 180 pg/mL is elevated rather than suppressed, which would be atypical for vitamin D toxicity. In classic vitamin D toxicity, PTH should be suppressed (<20 pg/mL) due to negative feedback from hypercalcemia. This PTH elevation may represent concurrent primary hyperparathyroidism or a laboratory reporting issue.
*Primary hypothyroidism*
- While the patient has elevated TSH (9 μU/mL), hypothyroidism typically causes **hypocalcemia** or normocalcemia, not hypercalcemia.
- The hypercalcemia with the patient's supplement use points to a different etiology.
*Excess calcium carbonate intake*
- Excess calcium carbonate intake could cause hypercalcemia but typically leads to **low phosphorus** due to calcium-phosphate binding in the gut and renal excretion.
- **Milk-alkali syndrome** (from excess calcium carbonate) presents with hypercalcemia, metabolic alkalosis, and renal insufficiency. The patient's normal bicarbonate (22 mEq/L) makes this less likely.
*Primary hyperparathyroidism*
- **Primary hyperparathyroidism** presents with **hypercalcemia** and **elevated PTH**, but classically causes **hypophosphatemia** due to PTH's phosphaturic effect.
- This patient has normal to mildly elevated phosphorus (4.6 mg/dL), which is atypical for primary hyperparathyroidism where phosphorus is usually low (<2.5 mg/dL).
- The history of new supplement use makes an exogenous cause (vitamin D toxicity) more likely than a parathyroid adenoma.
*Vitamin A toxicity*
- **Vitamin A toxicity** can cause hypercalcemia but typically presents with distinctive features including **dry skin**, **cheilosis**, **alopecia**, **hepatomegaly**, and **pseudotumor cerebri** (increased intracranial pressure).
- These characteristic findings are not present in this patient, making vitamin A toxicity less likely than vitamin D toxicity given the supplement history.
Question 36: A 58-year-old female presents with a two-month history of intermittent non-bloody diarrhea. She reports that she has been following a raw food diet for six months to help her lose weight. The patient’s medical history is significant for anxiety, treated with fluvoxamine, and osteopenia. She reports her mother has lactose intolerance and has recently been diagnosed with osteoporosis. The patient denies any tobacco or alcohol use. When asked about recent travel, she reports she returned three months ago from a mission trip in Uganda. The patient’s temperature is 99°F (37.2°C), blood pressure is 130/78 mmHg, pulse is 70/min, and respirations are 14/min with an oxygen saturation of 98% O2 on room air. On physical exam, a new-onset systolic ejection murmur is noted and is heard loudest at the left second intercostal space. Which of the following may develop in this patient?
A. Decreased levels of chromogranin A
B. Vitamin D deficiency
C. Positive hydrogen breath test
D. Low platelet count
E. Niacin deficiency (Correct Answer)
Explanation: ***Niacin deficiency***
- This patient most likely has **carcinoid syndrome** from a carcinoid tumor (possibly acquired during travel to Uganda or from chronic gastrointestinal pathology).
- The classic triad includes: **diarrhea**, **flushing**, and **right-sided heart valve disease** (explaining the new systolic ejection murmur at the left 2nd intercostal space - pulmonary valve area).
- Carcinoid tumors produce excessive **serotonin** by diverting **tryptophan** metabolism away from **niacin (vitamin B3) synthesis**.
- This leads to **pellagra** (niacin deficiency) with the "3 D's": **diarrhea, dermatitis, and dementia**.
- The raw food diet and chronic diarrhea may contribute to malabsorption, further increasing deficiency risk.
*Decreased levels of chromogranin A*
- **Chromogranin A** is a biomarker for neuroendocrine tumors and would be **elevated** (not decreased) in carcinoid syndrome.
- This option represents the opposite of what would occur in this patient with suspected carcinoid syndrome.
*Vitamin D deficiency*
- While the patient has **osteopenia** and risk factors for vitamin D deficiency, this does not explain the constellation of **diarrhea plus cardiac murmur**.
- Vitamin D deficiency primarily affects bone health and does not cause the valvular heart disease seen in this patient.
*Positive hydrogen breath test*
- A positive hydrogen breath test indicates **lactose intolerance** or **small intestinal bacterial overgrowth (SIBO)**.
- While the patient's mother has lactose intolerance, this would not explain the **new cardiac murmur** or the full clinical picture of carcinoid syndrome.
*Low platelet count*
- **Thrombocytopenia** is not a characteristic feature of carcinoid syndrome.
- The patient's symptoms and physical findings do not suggest a primary hematologic disorder.
Question 37: A 25-year-old woman first presented to your clinic due to morning stiffness, symmetrical arthralgia in her wrist joints, and fatigue. She had a blood pressure of 132/74 mm Hg and heart rate of 84/min. Physical examination revealed tenderness to palpation of both wrists but full range of motion. Anti-citrullinated protein antibodies were positive and ESR was above normal ranges. She was started on methotrexate therapy. She returns for follow up 2 months later and is found to have megaloblastic anemia. What is the mechanism of action of methotrexate?
A. Inhibits vitamin B12 activation
B. Intercalates into strands of DNA
C. Elevates methylmalonic acid levels
D. Elevates tetrahydrofolate levels
E. Inhibits dihydrofolate reductase (Correct Answer)
Explanation: ***Inhibits dihydrofolate reductase***
- **Methotrexate** is a **folate analog** that competitively inhibits **dihydrofolate reductase (DHFR)**, an enzyme essential for converting dihydrofolate to tetrahydrofolate.
- This inhibition blocks the synthesis of purines and pyrimidines, crucial for DNA synthesis and cellular proliferation, thereby suppressing immune cell activity in conditions like rheumatoid arthritis.
*Inhibits vitamin B12 activation*
- **Methotrexate** does not directly inhibit **vitamin B12 activation**; its primary mechanism is antagonism of folate metabolism.
- While vitamin B12 is crucial for DNA synthesis, its activation pathway is distinct from the dihydrofolate reductase pathway.
*Intercalates into strands of DNA*
- **Methotrexate** does not **intercalate into DNA strands**; this mechanism is characteristic of certain **chemotherapeutic agents** that insert themselves between base pairs, causing DNA damage and inhibiting replication.
- Methotrexate's action is upstream, targeting folate metabolism required for DNA precursor synthesis.
*Elevates methylmalonic acid levels*
- **Elevated methylmalonic acid** levels are a hallmark of **vitamin B12 deficiency**, as vitamin B12 is a cofactor for methylmalonyl-CoA mutase.
- Methotrexate's mechanism is related to **folate pathway inhibition**, and while it can lead to megaloblastic anemia, it does not directly elevate methylmalonic acid.
*Elevates tetrahydrofolate levels*
- **Methotrexate** *inhibits* the conversion of dihydrofolate to **tetrahydrofolate**, thus *decreasing* rather than elevating tetrahydrofolate levels.
- Lowering **tetrahydrofolate** levels is precisely how methotrexate exerts its therapeutic and adverse effects by impairing nucleotide synthesis.
Question 38: A 2-year-old boy is brought in by his parents to his pediatrician. The boy was born by spontaneous vaginal delivery at 39 weeks and 5 days after a normal pregnancy. The boy has received all age-appropriate vaccinations as of his last visit at 18 months of age. Of note, the boy has confirmed sickle cell disease and the only medication he takes is penicillin prophylaxis. The parents state that they plan on enrolling their son in a daycare, which requires documentation of up-to-date vaccinations. The pediatrician states that their son needs an additional vaccination at this visit, which is a polysaccharide vaccine that is not conjugated to protein. Which of the following matches this description?
A. Pneumovax (Correct Answer)
B. Menactra
C. Prevnar
D. Hib vaccine
E. Live attenuated influenza vaccine
Explanation: ***Pneumovax***
- **Pneumovax** (PCV23, PPSV23) is a **polysaccharide vaccine** that is not conjugated to a protein carrier. Children with **sickle cell disease** should receive this vaccine due to their immunocompromised state and increased risk of encapsulated bacterial infections.
- The Centers for Disease Control and Prevention (CDC) recommends PPSV23 for children aged 2 years and older with chronic medical conditions such as **sickle cell disease**, usually administered 8 weeks after their last PCV13 dose.
*Menactra*
- **Menactra** is a **quadrivalent meningococcal conjugate vaccine** (MCV4), meaning it contains a polysaccharide antigen conjugated to a protein carrier.
- This vaccine primarily targets *Neisseria meningitidis* and is different from the pneumococcal vaccine required here.
*Prevnar*
- **Prevnar** (PCV13) is a **pneumococcal conjugate vaccine**, meaning its polysaccharide antigens are conjugated to a protein carrier.
- While important for children with sickle cell disease, the question specifically asks for a vaccination that is a **polysaccharide vaccine that is not conjugated to protein**.
*Hib vaccine*
- The **Hib vaccine** (against *Haemophilus influenzae* type b) is a **conjugate vaccine**, meaning its polysaccharide capsule is linked to a protein carrier to enhance immunogenicity, particularly in infants.
- This vaccine is typically given earlier in childhood and is not the "additional" unconjugated polysaccharide vaccine described.
*Live attenuated influenza vaccine*
- The **live attenuated influenza vaccine (LAIV)** is a live virus vaccine, not a polysaccharide vaccine.
- It is also contraindicated in individuals with certain immunocompromising conditions, such as some patients with sickle cell disease.
Question 39: A 57-year-old man presents to the emergency department with fatigue. He states that his symptoms started yesterday and have been worsening steadily. The patient endorses a recent weight loss of 7 pounds this past week and states that he feels diffusely itchy. The patient has a past medical history of alcohol abuse, obesity, asthma, and IV drug use. His current medications include metformin, atorvastatin, albuterol, and fluticasone. In addition, the patient admits to smoking and drinking more than usual lately due to the stress he has experienced. His temperature is 98.7°F (37.1°C), blood pressure is 130/75 mmHg, pulse is 90/min, respirations are 15/min, and oxygen saturation is 98% on room air. Physical exam is notable for an ill-appearing man. The patient's skin appears yellow. Abdominal exam is notable for right upper quadrant tenderness. Cardiac and pulmonary exams are within normal limits. Laboratory values are ordered as seen below:
Hemoglobin: 14 g/dL
Hematocrit: 42%
Leukocyte count: 5,500 cells/mm^3 with normal differential
Platelet count: 70,000/mm^3
Partial thromboplastin time: 92 seconds
Prothrombin time: 42 seconds
AST: 1110 U/L
ALT: 990 U/L
Which of the following is most likely to be found in this patient's history?
A. Recent antibiotic treatment with gentamicin
B. Appropriate acute management of a deep vein thrombosis
C. Decreased UDP-glucuronosyltransferase activity at birth
D. Prosthetic valve with appropriate post-operative care
E. Severe migraine headaches treated with acetaminophen (Correct Answer)
Explanation: ***Severe migraine headaches treated with acetaminophen***
- The patient's presentation with **acute liver failure** (elevated AST/ALT, coagulopathy, jaundice) in the context of increased stress and likely increased medication use, strongly suggests **acetaminophen overdose** as the cause. Given his past medical history of alcohol abuse further increases his risk of liver injury with acetaminophen.
- While other etiologies such as acute viral hepatitis or ischemic hepatitis should be considered, acetaminophen overdose is the most common cause of acute liver failure.
*Recent antibiotic treatment with gentamicin*
- **Gentamicin** is an **aminoglycoside antibiotic** primarily associated with **nephrotoxicity** and **ototoxicity**, not acute liver failure.
- Liver dysfunction is not a typical adverse effect of gentamicin, making it an unlikely cause of the patient's symptoms.
*Appropriate acute management of a deep vein thrombosis*
- Treatment for deep vein thrombosis typically involves **anticoagulants** such as heparin or warfarin. While these medications can rarely cause liver injury, the severe and acute elevation in liver enzymes and coagulopathy seen here points away from a standard anticoagulant side effect.
- The clinical picture aligns much more closely with a direct hepatotoxic injury rather than an idiosyncratic reaction to anticoagulation.
*Decreased UDP-glucuronosyltransferase activity at birth*
- **Decreased UDP-glucuronosyltransferase (UGT) activity** at birth is characteristic of **Crigler-Najjar syndrome** or **Gilbert's syndrome**, which cause **unconjugated hyperbilirubinemia**.
- These are typically chronic conditions that present earlier in life and do not cause acute, severe hepatocellular injury with massively elevated AST/ALT and coagulopathy.
*Prosthetic valve with appropriate post-operative care*
- A prosthetic heart valve, even with appropriate post-operative care, is not directly linked to acute liver failure.
- While complications like endocarditis or hemolysis could cause some liver involvement, they would not typically present with this constellation of severe acute symptoms and laboratory findings.
Question 40: A 63-year-old man with inoperable esophageal carcinoma undergoes palliative chemoradiotherapy. Four hours after his first infusion of carboplatin and paclitaxel, he develops nausea and 3 episodes of vomiting and dry heaving. This adverse reaction is caused by stimulation of a brain region on the floor of the fourth ventricle. Chemotherapeutic drugs are able to stimulate this region because of the absence of a cell junction that is composed of which of the following proteins?
A. Claudins and occludins (Correct Answer)
B. Integrins
C. Cadherins and catenins
D. Connexins
E. Desmogleins and desmocollins
Explanation: ***Claudins and occludins***
- The **area postrema**, located on the floor of the fourth ventricle, is a **chemoreceptor trigger zone (CTZ)** that detects toxins in the blood.
- This region lacks a fully functional **blood-brain barrier** due to the absence of tight junctions, which are primarily composed of **claudins and occludins**, allowing chemotherapeutic agents to stimulate it and induce nausea and vomiting.
*Integrins*
- **Integrins** are primarily involved in **cell-matrix adhesion**, connecting the cell cytoskeleton to the extracellular matrix.
- They are not the primary components of **tight junctions** that form the blood-brain barrier.
*Cadherins and catenins*
- **Cadherins** are crucial for **cell-cell adhesion** in adherens junctions and desmosomes, and they link to the actin cytoskeleton via **catenins**.
- While important for cell adhesion, they are not the main proteins forming the **occluding seal** of tight junctions.
*Connexins*
- **Connexins** are the structural proteins that form **gap junctions**, which allow for direct communication and passage of small molecules between adjacent cells.
- They are not involved in forming the **impermeable barrier** characteristic of tight junctions.
*Desmogleins and desmocollins*
- **Desmogleins** and **desmocollins** are specific types of cadherins found in **desmosomes**, which provide strong cell-cell adhesion and resistance to mechanical stress.
- Desmosomes are different from **tight junctions**, which prevent paracellular diffusion.
