Opportunistic infections — MCQs

10 questions

For which of the following patients would you recommend prophylaxis against mycobacterium avium-intracellulare?

A 58-year-old woman with HIV infection is brought to the emergency department because of a 2-week history of headaches, blurred vision, and confusion. Her current medications include antiretroviral therapy and trimethoprim-sulfamethoxazole. Neurological examination shows ataxia and memory impairment. Her CD4+ T-lymphocyte count is 90/μL. Cerebrospinal fluid analysis shows lymphocytic predominant pleocytosis, and PCR is positive for Epstein-Barr virus DNA. An MRI of the brain with contrast shows a solitary, weakly ring-enhancing lesion with well-defined borders involving the corpus callosum. Which of the following is the most likely diagnosis?

A 44-year-old man is brought to the emergency department by his daughter for a 1-week history of right leg weakness, unsteady gait, and multiple falls. During the past 6 months, he has become more forgetful and has sometimes lost his way along familiar routes. He has been having difficulties operating simple kitchen appliances such as the dishwasher and the coffee maker. He has recently become increasingly paranoid, agitated, and restless. He has HIV, hypertension, and type 2 diabetes mellitus. His last visit to a physician was more than 2 years ago, and he has been noncompliant with his medications. His temperature is 37.2 °C (99.0 °F), blood pressure is 152/68 mm Hg, pulse is 98/min, and respirations are 14/min. He is somnolent and slightly confused. He is oriented to person, but not place or time. There is mild lymphadenopathy in the cervical, axillary, and inguinal areas. Neurological examination shows right lower extremity weakness with normal tone and no other focal deficits. Laboratory studies show: Hemoglobin 9.2 g/dL Leukocyte count 3600/mm3 Platelet count 140,000/mm3 CD4+ count 56/μL HIV viral load > 100,000 copies/mL Serum Cryptococcal antigen negative Toxoplasma gondii IgG positive An MRI of the brain shows disseminated, nonenhancing white matter lesions with no mass effect. Which of the following is the most likely diagnosis?

A 40-year-old man with AIDS comes to the physician because of a 3-week history of intermittent fever, abdominal pain, and diarrhea. He has also had a nonproductive cough and a 3.6-kg (8-lb) weight loss in this period. He was treated for pneumocystis pneumonia 2 years ago. He has had skin lesions on his chest for 6 months. Five weeks ago, he went on a week-long hiking trip in Oregon. Current medications include efavirenz, tenofovir, and emtricitabine. He says he has had trouble adhering to his medication. His temperature is 38.3°C (100.9°F), pulse is 96/min, and blood pressure is 110/70 mm Hg. Examination shows oral thrush on his palate and a white, non-scrapable plaque on the left side of the tongue. There is axillary and inguinal lymphadenopathy. There are multiple violaceous plaques on the chest. Crackles are heard on auscultation of the chest. Abdominal examination shows mild, diffuse tenderness throughout the lower quadrants. The liver is palpated 2 to 3 cm below the right costal margin, and the spleen is palpated 1 to 2 cm below the left costal margin. Laboratory studies show: Hemoglobin 12.2 g/dL Leukocyte count 4,800/mm3 CD4+ T-lymphocytes 44/mm3 (Normal ≥ 500 mm3) Platelet count 258,000/mm3 Serum Na+ 137 mEq/L Cl- 102 mEq/L K+ 4.9 mEq/L Alkaline phosphatase 202 U/L One set of blood culture grows acid-fast organisms. A PPD skin test shows 4 mm of induration. Which of the following is the most appropriate pharmacotherapy for this patient's condition?

A 34-year-old man comes to the physician for a routine health maintenance examination. He was diagnosed with HIV 8 years ago. He is currently receiving triple antiretroviral therapy. He is sexually active and uses condoms consistently. He is planning a trip to Thailand with his partner to celebrate his 35th birthday in 6 weeks. His last tetanus and diphtheria booster was given 4 years ago. He received three vaccinations against hepatitis B 5 years ago. He had chickenpox as a child. Other immunization records are unknown. Vital signs are within normal limits. Cardiopulmonary examination shows no abnormalities. Leukocyte count shows 8,700/mm3, and CD4+ T-lymphocyte count is 480 cells/mm3 (Normal ≥ 500); anti-HBs is 150 mIU/mL. Which of the following recommendations is most appropriate at this time?

A 33-year-old man with HIV comes to the physician because of a nonproductive cough and shortness of breath for 3 weeks. He feels tired after walking up a flight of stairs and after long conversations on the phone. He appears chronically ill. His temperature is 38.5°C (101.3°F), and pulse is 110/min. Pulse oximetry on room air shows an oxygen saturation of 95%. Upon walking, his oxygen saturation decreases to 85%. Cardiopulmonary examination is normal. Laboratory studies show a CD4+ T-lymphocyte count of 176/mm3 (N > 500). Results of urine Legionella antigen testing are negative. A CT scan of the chest shows diffuse, bilateral ground-glass opacities. Microscopic examination of fluid obtained from bronchoalveolar lavage will most likely show which of the following findings?

An HIV-positive patient with a CD4+ count of 45 is receiving recommended first-line treatment for a case of cytomegalovirus retinitis. Coadministration with which of the following agents would be most likely to precipitate a deficiency of neutrophils in this patient?

A 33-year-old HIV-positive male is seen in clinic for follow-up care. When asked if he has been adhering to his HIV medications, the patient exclaims that he has been depressed, thus causing him to not take his medication for six months. His CD4+ count is now 33 cells/mm3. What medication(s) should he take in addition to his anti-retroviral therapy?

A 57-year-old woman with non-small cell lung cancer comes to the physician 4 weeks after her tumor was resected. She takes no medications. The physician starts her on a treatment regimen that includes vinblastine. This treatment puts the patient at highest risk for which of the following?

Q10

A 37-year-old man presents to the emergency department for a persistent fever. The patient states he has felt unwell for the past week and has felt subjectively febrile. The patient has a past medical history of a suicide attempt and alcohol abuse. He is not currently taking any medications. The patient admits to using heroin and cocaine and drinking 5-8 alcoholic drinks per day. His temperature is 103°F (39.4°C), blood pressure is 92/59 mmHg, pulse is 110/min, respirations are 20/min, and oxygen saturation is 96% on room air. Cardiopulmonary exam is notable for a systolic murmur heard best along the left sternal border. Dermatologic exam reveals scarring in the antecubital fossa. Which of the following is the next best step in management?

Opportunistic infections US Medical PG Practice Questions and MCQs

Question 1: For which of the following patients would you recommend prophylaxis against mycobacterium avium-intracellulare?

A. 30-year old HIV positive male with CD4 count of 20 cells/microliter and a viral load of < 50 copies/mL (Correct Answer)
B. 22-year old HIV positive female with CD4 count of 750 cells/microliter and a viral load of 500,000 copies/mL
C. 45-year old HIV positive female with CD4 count of 250 cells/microliter and a viral load of 100,000 copies/mL
D. 50-year old HIV positive female with CD4 count of 150 cells/microliter and a viral load of < 50 copies/mL
E. 36-year old HIV positive male with CD4 count of 75 cells/microliter and an undetectable viral load

Explanation: ***30-year old HIV positive male with CD4 count of 20 cells/microliter and a viral load of < 50 copies/mL*** - Prophylaxis against **Mycobacterium avium complex (MAC)** is recommended for HIV-positive individuals with a **CD4 count below 50 cells/µL** to prevent disseminated MAC infection. - While an undetectable viral load suggests effective antiretroviral therapy (ART) in general, the extremely low CD4 count indicates severe immunosuppression, making prophylaxis crucial. *36-year old HIV positive male with CD4 count of 75 cells/microliter and an undetectable viral load* - The **CD4 count of 75 cells/µL** is above the threshold of 50 cells/µL for MAC prophylaxis, even though it's still low. - An **undetectable viral load** indicates successful ART, which generally helps improve immune function over time, albeit slowly in this CD4 range. *22-year old HIV positive female with CD4 count of 750 cells/microliter and a viral load of 500,000 copies/mL* - A **CD4 count of 750 cells/µL** is well above the threshold for MAC prophylaxis, indicating relatively preserved immune function. - Although the **viral load is very high**, suggesting uncontrolled HIV replication, the immune system is currently strong enough to ward off MAC. *45-year old HIV positive female with CD4 count of 250 cells/microliter and a viral load of 100,000 copies/mL* - A **CD4 count of 250 cells/µL** is above the threshold for MAC prophylaxis, which is 50 cells/µL. - While the **high viral load** implies an increased risk for opportunistic infections over time, other specific prophylaxes (e.g., PCP if <200) would be considered earlier. *50-year old HIV positive female with CD4 count of 150 cells/microliter and a viral load of < 50 copies/mL* - A **CD4 count of 150 cells/µL** is above the threshold for MAC prophylaxis (50 cells/µL). - An **undetectable viral load** is a positive sign of ART efficacy, but this patient would still require prophylaxis for **Pneumocystis jirovecii pneumonia (PCP)**, as her CD4 count is below 200 cells/µL.

Question 2: A 58-year-old woman with HIV infection is brought to the emergency department because of a 2-week history of headaches, blurred vision, and confusion. Her current medications include antiretroviral therapy and trimethoprim-sulfamethoxazole. Neurological examination shows ataxia and memory impairment. Her CD4+ T-lymphocyte count is 90/μL. Cerebrospinal fluid analysis shows lymphocytic predominant pleocytosis, and PCR is positive for Epstein-Barr virus DNA. An MRI of the brain with contrast shows a solitary, weakly ring-enhancing lesion with well-defined borders involving the corpus callosum. Which of the following is the most likely diagnosis?

A. Glioblastoma multiforme
B. Cerebral toxoplasmosis
C. Primary cerebral lymphoma (Correct Answer)
D. Progressive multifocal leukoencephalopathy
E. AIDS dementia

Explanation: ***Primary cerebral lymphoma*** - The combination of **HIV infection** with a very low **CD4 count (<100/μL)**, **weakly ring-enhancing solitary lesion** in the corpus callosum, Epstein-Barr virus (EBV) DNA in CSF, and typical neurological symptoms points strongly to **primary cerebral lymphoma (PCL)**. - PCL is a common **AIDS-defining illness** and is highly associated with **EBV infection** in immunocompromised individuals. *Glioblastoma multiforme* - While GBM is a primary brain tumor, it typically presents with a **strongly and irregularly enhancing lesion**, often with a **necrotic center**, rather than a solitary, weakly enhancing lesion. - GBM is not directly associated with **HIV infection** or **EBV DNA in CSF**, which are key features in this case. *Cerebral toxoplasmosis* - Cerebral toxoplasmosis typically presents with **multiple ring-enhancing lesions**, often in the **basal ganglia**, rather than a solitary lesion as described. - Diagnosis is usually confirmed by **serology for *Toxoplasma gondii*** and a positive response to empiric anti-toxoplasma therapy, not EBV DNA in CSF. *Progressive multifocal leukoencephalopathy* - PML is characterized by **non-enhancing white matter lesions** on MRI, rather than a ring-enhancing lesion. - It is caused by the **JC virus**, not EBV, and typically presents with **rapidly progressive neurological deficits** without mass effect. *AIDS dementia* - AIDS dementia complex (now HIV-associated neurocognitive disorder) presents as **diffuse cerebral atrophy** and **white matter changes** on MRI, without focal or ring-enhancing lesions. - It is a diagnosis of exclusion in HIV patients with cognitive decline, and the presence of a focal lesion with mass effect points to another etiology.

Question 3: A 44-year-old man is brought to the emergency department by his daughter for a 1-week history of right leg weakness, unsteady gait, and multiple falls. During the past 6 months, he has become more forgetful and has sometimes lost his way along familiar routes. He has been having difficulties operating simple kitchen appliances such as the dishwasher and the coffee maker. He has recently become increasingly paranoid, agitated, and restless. He has HIV, hypertension, and type 2 diabetes mellitus. His last visit to a physician was more than 2 years ago, and he has been noncompliant with his medications. His temperature is 37.2 °C (99.0 °F), blood pressure is 152/68 mm Hg, pulse is 98/min, and respirations are 14/min. He is somnolent and slightly confused. He is oriented to person, but not place or time. There is mild lymphadenopathy in the cervical, axillary, and inguinal areas. Neurological examination shows right lower extremity weakness with normal tone and no other focal deficits. Laboratory studies show: Hemoglobin 9.2 g/dL Leukocyte count 3600/mm3 Platelet count 140,000/mm3 CD4+ count 56/μL HIV viral load > 100,000 copies/mL Serum Cryptococcal antigen negative Toxoplasma gondii IgG positive An MRI of the brain shows disseminated, nonenhancing white matter lesions with no mass effect. Which of the following is the most likely diagnosis?

A. Vascular dementia
B. Primary CNS lymphoma
C. Neurocysticercosis
D. Cerebral toxoplasmosis
E. Progressive multifocal leukoencephalopathy (Correct Answer)

Explanation: ***Progressive multifocal leukoencephalopathy*** - The patient's severe **immunosuppression** (CD4 count 56/μL) and **non-enhancing white matter lesions** disseminated throughout the brain are highly characteristic of **PML**, caused by the **JC virus**. - **Progressive neurological deficits** including cognitive decline, motor weakness, and personality changes are typical presentations of PML in advanced HIV. *Vascular dementia* - While the patient has **hypertension** and a history of falls, the MRI findings of **disseminated non-enhancing white matter lesions** are not classic for vascular dementia, which typically shows lacunar infarcts or larger areas of ischemic damage. - The rapid progression of symptoms and severe immunosuppression also point away from typical vascular dementia as the primary cause. *Primary CNS lymphoma* - **Primary CNS lymphoma** in HIV patients usually presents as **solitary or multiple mass lesions** that are typically **ring-enhancing** on MRI, which contradicts the described non-enhancing lesions. - While it can cause neurological deficits, the MRI findings are a strong differentiating factor. *Neurocysticercosis* - **Neurocysticercosis** is caused by the parasite *Taenia solium* and is more common in endemic areas; MRI typically shows **cysts, calcifications, or enhancing lesions**, often with associated edema. - The patient's non-enhancing white matter lesions and high HIV viral load make this diagnosis less likely, despite the global prevalence of the infection. *Cerebral toxoplasmosis* - **Cerebral toxoplasmosis** is common in HIV patients with low CD4 counts and positive *Toxoplasma gondii* IgG, but it typically presents with **multiple ring-enhancing lesions** on MRI, often with **mass effect**. - The absence of enhancement and mass effect on MRI makes toxoplasmosis less probable despite the positive IgG serology.

Question 4: A 40-year-old man with AIDS comes to the physician because of a 3-week history of intermittent fever, abdominal pain, and diarrhea. He has also had a nonproductive cough and a 3.6-kg (8-lb) weight loss in this period. He was treated for pneumocystis pneumonia 2 years ago. He has had skin lesions on his chest for 6 months. Five weeks ago, he went on a week-long hiking trip in Oregon. Current medications include efavirenz, tenofovir, and emtricitabine. He says he has had trouble adhering to his medication. His temperature is 38.3°C (100.9°F), pulse is 96/min, and blood pressure is 110/70 mm Hg. Examination shows oral thrush on his palate and a white, non-scrapable plaque on the left side of the tongue. There is axillary and inguinal lymphadenopathy. There are multiple violaceous plaques on the chest. Crackles are heard on auscultation of the chest. Abdominal examination shows mild, diffuse tenderness throughout the lower quadrants. The liver is palpated 2 to 3 cm below the right costal margin, and the spleen is palpated 1 to 2 cm below the left costal margin. Laboratory studies show: Hemoglobin 12.2 g/dL Leukocyte count 4,800/mm3 CD4+ T-lymphocytes 44/mm3 (Normal ≥ 500 mm3) Platelet count 258,000/mm3 Serum Na+ 137 mEq/L Cl- 102 mEq/L K+ 4.9 mEq/L Alkaline phosphatase 202 U/L One set of blood culture grows acid-fast organisms. A PPD skin test shows 4 mm of induration. Which of the following is the most appropriate pharmacotherapy for this patient's condition?

A. Rifampin and isoniazid
B. Voriconazole
C. Erythromycin
D. Amphotericin B and itraconazole
E. Azithromycin and ethambutol (Correct Answer)

Explanation: ***Azithromycin and ethambutol*** - This patient presents with disseminated **Mycobacterium avium complex (MAC)** infection, evidenced by systemic symptoms (fever, weight loss, abdominal pain, diarrhea), **hepatosplenomegaly**, elevated alkaline phosphatase, and the isolation of **acid-fast organisms** from blood cultures in an HIV-positive patient with a **CD4 count of 44 cells/mm³**. Azithromycin (or clarithromycin) in combination with ethambutol is the recommended treatment for disseminated MAC. - The diagnosis is further supported by the patient's history of non-adherence to ART, leading to a severely immunocompromised state, and the fact that MAC is a common opportunistic infection in patients with **AIDS and CD4 counts below 50 cells/mm³**. *Rifampin and isoniazid* - This combination is part of the standard regimen for **Mycobacterium tuberculosis** infection. While the patient has acid-fast organisms, his low **CD4 count** and disseminated symptoms are more characteristic of MAC than typical pulmonary tuberculosis, especially given the rapid dissemination. - The PPD induration of 4mm is not diagnostic of active tuberculosis in an immunocompromised patient; a PPD response can be blunted in severe immunodeficiency. *Voriconazole* - **Voriconazole** is an antifungal medication primarily used to treat serious fungal infections, such as invasive aspergillosis, candidiasis, and scedosporiosis. - The patient's presentation with acid-fast organisms from blood culture indicates a bacterial infection, not a fungal infection, making voriconazole inappropriate. *Erythromycin* - **Erythromycin** is a macrolide antibiotic, but it is not the preferred or effective treatment for disseminated MAC. While macrolides like azithromycin and clarithromycin are used, erythromycin has generally fallen out of favor for mycobacterial infections due to its inferior efficacy and higher gastrointestinal side effects compared to newer macrolides. - It is typically used for common bacterial respiratory tract infections, skin infections, and sexually transmitted infections, but not for opportunistic mycobacterial infections in immunocompromised patients. *Amphotericin B and itraconazole* - **Amphotericin B** and **itraconazole** are antifungals used for systemic fungal infections (e.g., blastomycosis, histoplasmosis, cryptococcosis, aspergillosis). - The isolation of **acid-fast organisms** from blood culture confirms a mycobacterial infection, not a fungal one, hence these antifungals would not be effective.

Question 5: A 34-year-old man comes to the physician for a routine health maintenance examination. He was diagnosed with HIV 8 years ago. He is currently receiving triple antiretroviral therapy. He is sexually active and uses condoms consistently. He is planning a trip to Thailand with his partner to celebrate his 35th birthday in 6 weeks. His last tetanus and diphtheria booster was given 4 years ago. He received three vaccinations against hepatitis B 5 years ago. He had chickenpox as a child. Other immunization records are unknown. Vital signs are within normal limits. Cardiopulmonary examination shows no abnormalities. Leukocyte count shows 8,700/mm3, and CD4+ T-lymphocyte count is 480 cells/mm3 (Normal ≥ 500); anti-HBs is 150 mIU/mL. Which of the following recommendations is most appropriate at this time?

A. Yellow fever vaccine
B. Hepatitis B vaccine
C. Tetanus, diphtheria, pertussis vaccine (Tdap)
D. Measles, mumps, rubella vaccine
E. No vaccination (Correct Answer)

Explanation: ***Correct: No vaccination*** - Given the patient's current immunization status and clinical scenario, **none of the listed vaccines are indicated at this time**. - His CD4+ count of 480 cells/mm³ indicates relatively preserved immune function on effective antiretroviral therapy. - His **anti-HBs level of 150 mIU/mL** demonstrates **adequate hepatitis B immunity** (protective level ≥10 mIU/mL). - His **tetanus-diphtheria booster was given 4 years ago**, and routine boosters are recommended every **10 years**, so he is not due for another 6 years. *Incorrect: Yellow fever vaccine* - **Thailand is not a yellow fever endemic country**, so yellow fever vaccination is **not required or recommended** for travel there. - Yellow fever vaccine is a **live attenuated vaccine** that can be given to HIV-positive patients with **CD4+ counts ≥200 cells/mm³** when travel to endemic areas (parts of Africa and South America) is necessary. - Since the patient has a CD4+ count of 480 and Thailand doesn't require this vaccine, this is not applicable. *Incorrect: Hepatitis B vaccine* - The patient's **anti-HBs level of 150 mIU/mL** indicates **adequate protective immunity** against hepatitis B. - A level ≥10 mIU/mL is considered protective, so **no booster is needed**. *Incorrect: Tetanus, diphtheria, pertussis vaccine (Tdap)* - **Tetanus-diphtheria boosters are recommended every 10 years**. - The patient received his last booster **4 years ago**, so he is **not due** for another booster at this time. - There is no specific indication for **pertussis vaccination** (e.g., pregnancy, close contact with infants). *Incorrect: Measles, mumps, rubella vaccine* - **MMR is a live attenuated vaccine** that is **contraindicated** in HIV-positive individuals with **CD4+ counts <200 cells/mm³**. - While this patient's CD4+ count is 480, MMR should only be given to HIV patients if they lack immunity and have CD4 ≥200. - There is **no documented need** for MMR based on the clinical scenario provided, and his immunity status to these infections is unknown. - Without evidence of susceptibility or specific exposure risk, vaccination is not indicated.

Question 6: A 33-year-old man with HIV comes to the physician because of a nonproductive cough and shortness of breath for 3 weeks. He feels tired after walking up a flight of stairs and after long conversations on the phone. He appears chronically ill. His temperature is 38.5°C (101.3°F), and pulse is 110/min. Pulse oximetry on room air shows an oxygen saturation of 95%. Upon walking, his oxygen saturation decreases to 85%. Cardiopulmonary examination is normal. Laboratory studies show a CD4+ T-lymphocyte count of 176/mm3 (N > 500). Results of urine Legionella antigen testing are negative. A CT scan of the chest shows diffuse, bilateral ground-glass opacities. Microscopic examination of fluid obtained from bronchoalveolar lavage will most likely show which of the following findings?

A. Silver-staining, disc-shaped cysts (Correct Answer)
B. Silver-staining, gram-negative bacilli
C. Septate, acute-angle branching hyphae
D. Gram-positive, catalase-positive cocci
E. Intracellular, acid-fast bacteria

Explanation: **Silver-staining, disc-shaped cysts** - The patient's presentation with **nonproductive cough**, **shortness of breath**, fever, and **exertional hypoxemia** (desaturation upon walking) in the context of **HIV with a low CD4+ count (176/mm3)** is highly suggestive of **Pneumocystis pneumonia (PCP)**. - **Pneumocystis jirovecii** (formerly *Pneumocystis carinii*) is the causative agent and is characterized by **disc-shaped cysts that stain with silver stains** (e.g., GMS stain) in bronchoalveolar lavage (BAL) fluid. *Silver-staining, gram-negative bacilli* - This description is characteristic of **Legionella pneumophila**, which can cause pneumonia, but the **urine Legionella antigen test was negative**, making this diagnosis less likely. - While Legionella is a gram-negative bacillus and can be stained with silver, the overall clinical picture and negative antigen test point away from it. *Septate, acute-branching hyphae* - This morphology is characteristic of **Aspergillus species**, which can cause invasive aspergillosis, particularly in immunocompromised patients. - However, aspergillosis typically presents with different radiological findings (e.g., nodules, cavitations, halo sign, or air crescent sign), and the clinical picture in this case is more typical of PCP. *Gram-positive, catalase-positive cocci* - This description is typical for **Staphylococcus aureus**, which can cause bacterial pneumonia. - While *S. aureus* can cause pneumonia in immunocompromised patients, the diffuse **ground-glass opacities** and exertional hypoxemia, coupled with a low CD4 count, are not typical for staphylococcal pneumonia. *Intracellular, acid-fast bacteria* - This morphology is characteristic of **Mycobacterium species**, such as **Mycobacterium tuberculosis** or **Mycobacterium avium complex (MAC)**. - While TB and MAC infections are common in HIV patients with low CD4 counts, they usually present with different radiological patterns (e.g., cavitations, lymphadenopathy for TB; disseminated disease for MAC) and the sudden onset of profound exertional hypoxemia is less typical.

Question 7: An HIV-positive patient with a CD4+ count of 45 is receiving recommended first-line treatment for a case of cytomegalovirus retinitis. Coadministration with which of the following agents would be most likely to precipitate a deficiency of neutrophils in this patient?

A. Ritonavir
B. Raltegravir
C. Foscarnet
D. Efavirenz
E. Zidovudine (Correct Answer)

Explanation: ***Zidovudine*** - **Zidovudine (AZT)** is a nucleoside reverse transcriptase inhibitor (NRTI) that is well-known for causing **myelosuppression**, particularly **neutropenia** and **anemia**. - In an HIV-positive patient with a low **CD4+ count** and concurrent treatment for **CMV retinitis** (which often involves drugs like ganciclovir that can also cause myelosuppression), adding zidovudine significantly increases the risk of severe neutropenia. *Ritonavir* - **Ritonavir** is a protease inhibitor primarily known for its role as a **pharmacokinetic booster** in HIV therapy, enhancing the levels of other antiretrovirals. - While it can cause gastrointestinal side effects and hepatotoxicity, **myelosuppression** and specifically neutropenia are not its primary or common adverse effects. *Raltegravir* - **Raltegravir** is an integrase strand transfer inhibitor (INSTI) generally well-tolerated with a favorable side effect profile. - Common side effects include headache, nausea, and fatigue, but it is **not typically associated with significant myelosuppression** or neutropenia. *Foscarnet* - **Foscarnet** is an antiviral agent used for treating CMV retinitis, particularly in cases of ganciclovir resistance. - Its major dose-limiting toxicities include **nephrotoxicity** and **electrolyte disturbances** (e.g., hypocalcemia, hypomagnesemia), not primarily neutropenia. *Efavirenz* - **Efavirenz** is a non-nucleoside reverse transcriptase inhibitor (NNRTI) associated with central nervous system side effects such as dizziness, insomnia, and vivid dreams. - While skin rash and hepatotoxicity can occur, **bone marrow suppression** leading to neutropenia is not a characteristic or frequent adverse effect of efavirenz.

Question 8: A 33-year-old HIV-positive male is seen in clinic for follow-up care. When asked if he has been adhering to his HIV medications, the patient exclaims that he has been depressed, thus causing him to not take his medication for six months. His CD4+ count is now 33 cells/mm3. What medication(s) should he take in addition to his anti-retroviral therapy?

A. Azithromycin and fluconazole
B. Azithromycin, dapsone, and fluconazole
C. Dapsone
D. Fluconazole
E. Azithromycin and trimethoprim-sulfamethoxazole (Correct Answer)

Explanation: ***Azithromycin and trimethoprim-sulfamethoxazole*** - With a **CD4+ count of 33 cells/mm3**, this patient is at high risk for **Pneumocystis jirovecii pneumonia (PJP)** and **Toxoplasma gondii encephalitis**, for which **trimethoprim-sulfamethoxazole (TMP-SMX)** is the prophylaxis of choice. - He is also at very high risk for **Mycobacterium avium complex (MAC) infection**, for which **azithromycin** is the recommended preventative treatment when the CD4 count is below 50 cells/mm3. *Azithromycin and fluconazole* - While **azithromycin** is indicated for MAC prophylaxis, **fluconazole** is typically used for **cryptococcal meningitis** or **candidiasis**, which are not the primary, immediate prophylactic concerns at this specific CD4 count unless there's evidence of these infections. - The most critical opportunistic infections to prevent at a CD4 count of 33 cells/mm3 are PJP, Toxoplasmosis, and MAC. *Azithromycin, dapsone, and fluconazole* - **Dapsone** can be used as an alternative for **PJP prophylaxis** if TMP-SMX is contraindicated, but it is not the first-line choice and does not cover toxoplasmosis as effectively as TMP-SMX alone. - **Fluconazole** again is not a primary prophylactic agent at this CD4 count in the absence of specific indications. *Dapsone* - **Dapsone** is an alternative for **PJP prophylaxis** and can also prevent **Toxoplasma gondii encephalitis** when combined with pyrimethamine, but it is not the first-line recommendation. - It does not provide coverage against **MAC infection**, which is a significant risk at this CD4 count. *Fluconazole* - **Fluconazole** is primarily used for **fungal infections** like **candidiasis** or **cryptococcosis**. - It does not prevent **PJP, Toxoplasmosis, or MAC**, which are the most critical prophylactic concerns for a patient with a CD4 count of 33 cells/mm3.

Question 9: A 57-year-old woman with non-small cell lung cancer comes to the physician 4 weeks after her tumor was resected. She takes no medications. The physician starts her on a treatment regimen that includes vinblastine. This treatment puts the patient at highest risk for which of the following?

A. Pulmonary embolism
B. Invasive fungal infection (Correct Answer)
C. Progressive multifocal leukoencephalopathy
D. Pulmonary fibrosis
E. Heart failure

Explanation: ***Invasive fungal infection*** - Vinblastine is an **antimitotic chemotherapy agent** that, like other chemotherapeutic agents, can cause **myelosuppression**. - **Myelosuppression** (particularly **neutropenia**) severely compromises the immune system, making patients highly susceptible to **opportunistic infections**, including invasive fungal infections. *Pulmonary embolism* - While cancer itself is a risk factor for **venous thromboembolism**, including pulmonary embolism, vinblastine itself **does not directly increase the risk** more than other chemotherapy agents. - The highest risk with vinblastine specifically relates to its impact on bone marrow. *Progressive multifocal leukoencephalopathy* - This is a rare, severe opportunistic infection of the brain caused by the **JC virus**, primarily seen in patients with **severe immunosuppression**, such as those with HIV/AIDS or on chronic immunosuppressive therapy (e.g., natalizumab). - While chemotherapy can cause immunosuppression, PML is not the most common or highest specific risk directly associated with vinblastine or its immediate, acute side effects compared to myelosuppression and opportunistic infections. *Pulmonary fibrosis* - **Pulmonary fibrosis** is a known side effect of certain chemotherapeutic agents like **bleomycin** and **busulfan**, but it is **not a primary or common adverse effect of vinblastine**. - The side effect profile of vinblastine primarily involves myelosuppression, neurotoxicity, and gastrointestinal effects. *Heart failure* - **Cardiotoxicity leading to heart failure** is a significant concern with certain chemotherapy drugs, particularly **anthracyclines** (e.g., doxorubicin) and some tyrosine kinase inhibitors. - **Vinblastine is not typically associated with cardiotoxicity or heart failure** as a primary or high-risk adverse effect.

Question 10: A 37-year-old man presents to the emergency department for a persistent fever. The patient states he has felt unwell for the past week and has felt subjectively febrile. The patient has a past medical history of a suicide attempt and alcohol abuse. He is not currently taking any medications. The patient admits to using heroin and cocaine and drinking 5-8 alcoholic drinks per day. His temperature is 103°F (39.4°C), blood pressure is 92/59 mmHg, pulse is 110/min, respirations are 20/min, and oxygen saturation is 96% on room air. Cardiopulmonary exam is notable for a systolic murmur heard best along the left sternal border. Dermatologic exam reveals scarring in the antecubital fossa. Which of the following is the next best step in management?

A. CT scan
B. Ultrasound
C. Chest radiograph
D. Blood cultures (Correct Answer)
E. Vancomycin and gentamicin

Explanation: ***Blood cultures*** - The patient's history of **intravenous drug use (IVDU)**, persistent fever, and a **new systolic murmur** strongly suggest **infective endocarditis**. - **Blood cultures** are crucial for identifying the causative organism and guiding appropriate antibiotic therapy, serving as the cornerstone of diagnosis in suspected endocarditis. *CT scan* - While CT scans can be useful for identifying complications of endocarditis (e.g., septic emboli in the brain or lungs), they are **not the initial diagnostic step** for identifying the source of infection. - CT scans expose the patient to **radiation** and are more expensive, making them less suitable as a first step compared to blood cultures. *Ultrasound* - An **echocardiogram** (a type of ultrasound) is essential for visualizing vegetations on heart valves, but it is typically performed *after* blood cultures reveal bacteremia to confirm the diagnosis and assess severity. - A general ultrasound of other body areas would be non-specific and **unlikely to pinpoint the cause** of persistent fever in this clinical context. *Chest radiograph* - A chest radiograph can identify **pulmonary infiltrates** or **septic emboli in the lungs**, which are potential complications of right-sided endocarditis (common in IVDU). - However, a chest radiograph **does not identify the causative organism** or confirm the primary diagnosis of endocarditis, making it a secondary investigation. *Vancomycin and gentamicin* - This combination represents a broad-spectrum antibiotic regimen often used for **empiric treatment of infective endocarditis**, particularly in IVDU patients due to concerns for MRSA or resistant streptococcal species. - While ultimately necessary, administering antibiotics *before* obtaining **blood cultures** can significantly reduce the yield of cultures and hinder definitive diagnosis and tailored treatment.

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