A 79-year-old woman presents to the Emergency Department from a nursing home with severe diarrhea and dehydration. The symptoms started yesterday and are associated with fever and abdominal pain. She has had approximately 15 nonbloody, watery bowel movements since then and has been getting weaker. Upon further questioning of the nursing home staff, she had pneumonia 1 week ago and is finishing treatment. Her other medical problems include hypothyroidism, hypertension, and coronary artery disease. Her temperature is 39.8°C, blood pressure is 96/64 mmHg, heart rate is 92 beats per minute, and respiratory rate is 18 breaths per minute. Initial screening laboratory values show a leukocyte count of 22,300/mm3 , a hemoglobin of 13.8 g/dL, and a platelet count of 480,000/mm3 . Further diagnostic workup is pending.
What is the most appropriate next step in management?
Oral vancomycin and IV metronidazole. This patient has a severe infection due to Clostridium difficile, which colonizes the intestinal tract and releases toxin A/B that damages the colonic mucosa. It is a very common nosocomial pathogen, and infection frequently occurs after antibiotics due to alteration of the gut flora. The severity can range from mild (loose stools without dehydration) to severe (profuse watery diarrhea, severe colitis, and toxic megacolon). Diagnosis can be made by testing the stool for C. difficile toxins, or with endoscopy showing pseudomembranous colitis. If C. difficile is suspected, the causative antibiotic should be stopped immediately and appropriate contact measures implemented (e.g., washing hands with soap and water upon entering and exiting the patient’s room). In addition, antibiotics should be started, which are based on the severity of disease. Severe C. difficile infection (indicated by >12 bowel movements per day, high fever, serum leukocyte count >15,000/mm3 , acute kidney injury, sepsis, age >65 or 70, etc.) should be treated with oral vancomycin since the drug has poor oral bioavailability, making it through the gut to act locally in the infected colon. Other options include oral vancomycin with IV metronidazole, or per rectal vancomycin with IV metronidazole (especially if the patient has an ileus). (C) Oral metronidazole alone is appropriate for mild infections; however, this patient is severely ill. (D) Oral vancomycin is preferred to IV vancomycin given its direct contact to infected colon.
(A) Iatrogenic hyperthyroidism can cause diarrhea, but would have other signs (marked tachycardia, mental status changes, etc.) without such a marked leukocytosis, as is seen in this patient. (B) Surgical colectomy is an option for severe infections based on abdominal CT results (e.g., bowel perforation, toxic megacolon), but it is not the next step in management for this patient.
A 32-year-old man is brought into the Emergency Department after he had a seizure. He has no history of a seizure disorder and there was no preceding trauma, new medications, or illicit drugs. On examination, his temperature is 38.9°C, blood pressure is 118/70 mmHg, heart rate is 90 beats per minute, and respiratory rate is 12 breaths per minute. He is lethargic and has a horizontal gaze palsy affecting the left eye. Appropriate laboratory values are sent, and a lumbar puncture and MRI (Figure below) are performed. The CSF studies show a large number of RBCs in each tube.
Which of the following therapies is most likely to be active against this condition?
Acyclovir. The only medication on the list that has activity against herpes simplex virus type 1 (HSV-1) is acyclovir. HSV is the most common cause of sporadic encephalitis and has a very high morbidity and mortality. It presents acutely with fever, mental status changes, and focal neurologic deficits; affected patients may also have symptoms of meningitis. Whereas meningitis is caused by inflammation of the meninges surrounding the brain (infection of the subarachnoid space), encephalitis is caused by inflammation of the brain parenchyma. There is frequently overlap of the two conditions (meningoencephalitis).
Other findings in the above vignette that suggest this diagnosis are elevated RBCs in the CSF in each tube (as opposed to a traumatic spinal tap, in which the concentration of RBCs would diminish with each tube), and inflammation of the left temporal lobe seen on MRI. HSV should be highly suspected in any patient with encephalitis, and the above findings are virtually diagnostic of HSV; however, the diagnosis can be confirmed with PCR or viral culture of the CSF. If suspected, empiric acyclovir should be started immediately. One potential adverse reaction of acyclovir is acute renal failure, which can occur secondary to crystal formation in the tubules.
(A) Dexamethasone is a strong corticosteroid that can be used in cases of S. pneumoniae meningitis, which is not the likely diagnosis based on the MRI showing encephalitis. (B, E) Ceftriaxone and vancomycin are used for empiric antibiotic treatment of meningitis. Ceftriaxone is effective against S. pneumoniae, N. meningitidis, and H. influenzae, and vancomycin is effective against cephalosporin-resistant S. pneumoniae and S. aureus. (C) Amphotericin B is used for cryptococcal meningitis, which is the most common manifestation of Cryptococcus neoformans in HIV patients.
A 60-year-old man with a history of hypertension and chronic obstructive pulmonary disease (COPD) presents to the Emergency Department complaining of fever and a productive cough. The symptoms started yesterday and have been progressive. He now also has vomiting, diarrhea, headache, and muscle and joint pain. His current medications include inhaled albuterol and ipratropium, hydrochlorothiazide, and lisinopril. He has a 30 pack-year smoking history and drinks alcohol moderately. He recently returned from a business trip, where he stayed in several hotels and ate all of his meals within these hotels. On examination, his temperature is 39.2°C with a heart rate of 110 beats per minute and a respiratory rate of 26 breaths per minute. Pulmonary examination reveals dullness to percussion in the left lower lobe with rales and bronchial breath sounds on auscultation. His laboratory values are shown below.
A urine dipstick shows 1+ protein and 1+ blood.
Which of the following is the most likely causative organism?
Legionella pneumophila. This patient has CAP with features of Legionnaires’ disease caused by L. pneumophila, which is the most common Legionella species to cause disease in humans. It is a common cause of CAP and HAP. Although Legionnaires’ disease can occur in any age group, it is more common in older patients who have a history of smoking or underlying lung disease. This patient likely acquired this infection from recent travel; outbreaks typically involve a water source such as hotel drinking water. It presents as pneumonia with fever, productive cough, and dyspnea and may also have symptoms of headache, myalgias/arthralgias, nausea/vomiting, and diarrhea. Laboratory values frequently show hyponatremia, renal and/or hepatic dysfunction, and hematuria/proteinuria. Diagnosis can be made with a urinary antigen test and culture on buffered charcoal yeast extract agar. Treatment is with a macrolide or fluoroquinolone antibiotic. This is a high-yield question for the shelf examination; when an elderly patient presents with pneumonia, hyponatremia, and diarrhea, suspect Legionella. (Of note, Legionella can also cause a mild, self-limited pulmonary condition called Pontiac fever, though this is less common than Legionnaires’ disease.)
Almost all of the answer choices are reasonable choices for CAP; however, the constellation of findings argues for Legionella over the other organisms. It is helpful to know the organisms associated with unique clinical syndromes (e.g., Legionnaires’ disease) and with unique circumstances (e.g., Nocardia in an immunosuppressed patient). (A) S. pneumoniae is the most common cause of pneumonia worldwide. (C) Klebsiella is common in alcoholics and nursing home patients; look for the buzzwords “currant jelly sputum” and “mucoid colonies.” (D) Pseudomonas is a common water-loving nosocomial pathogen that is often multidrug resistant (MDR). It is also very common in cystic fibrosis patients. (E) Mycoplasma and other “atypical” pneumonias are common in young, healthy patients. H. influenzae and Moraxella catarrhalis are common causes of pneumonia in COPD patients; however, the constellation of findings in this patient argues for Legionella over H. influenzae. Stenotrophomonas maltophilia is an opportunistic MDR organism that can cause HAP and VAP. Peptostreptococcus anaerobius is an anaerobic organism that is often found in cases of aspiration pneumonia.
A 46-year-old HIV-positive man is doing poorly on his antiretroviral regimen. He undergoes HIV genotyping and begins a new treatment regimen. Several days later, he follows up for routine blood work and reports feeling well with no adverse reactions. Blood work reveals a creatinine of 1.6 mg/dL (baseline 1.0 mg/dL), and a urinalysis shows hematuria, pyuria, and crystalluria.
Which of the following medications is most likely responsible?
Indinavir. Crystal nephropathy is a potential adverse reaction of indinavir, a protease inhibitor used in the treatment of HIV. Other protease inhibitors can cause crystalluria, but indinavir has a high incidence of this complication. Additional medications that can cause crystal nephropathy include methotrexate, acyclovir, and ethylene glycol. (A) Tenofovir is a nucleoside reverse transcriptase inhibitor (NRTI) that can cause renal failure, but the mechanism is not by crystal formation within the tubules. (B) Abacavir is another NRTI that has a high incidence of life-threatening hypersensitivity reactions, especially in patients who are HLA-B*5701 positive. (D) Efavirenz is nonnucleoside reverse transcriptase inhibitor (NNRTI) that causes depression and other CNS effects. (E) Maraviroc antagonizes CCR5 and inhibits entry of HIV into host cells; it can cause hepatotoxicity. Didanosine is an NRTI, and like other NRTIs it may cause lipodystrophy and lactic acidosis.
A 48-year-old man presents to the Emergency Department with fevers, headache, fatigue, and yellowing of his skin and eyes. The constitutional symptoms began 3 days ago, and he thought it was the flu. This morning, his girlfriend noticed that his eyes appeared yellow. He has a history of hypertension and Graves disease, which are both stable. The patient lives in rural New York and is a nature photographer. He has no pets and does not smoke. Initial laboratory values are significant for a hemoglobin of 9.6 mg/dL, a serum leukocyte count of 14,500/mm3 , and a serum lactate dehydrogenase of 210 U/L. His peripheral blood smear is shown in Figure below.
Which of the following is the most likely diagnosis?
Babesia microti. Babesiosis is caused by the parasite Babesia microti, which is carried by Ixodes ticks. Patients often present with nonspecific flu-like symptoms and a hemolytic anemia, which is indicated by this patient’s low hemoglobin and high serum lactate dehydrogenase. The peripheral blood smear shows the parasites within RBCs, confirming the diagnosis. If merozoites are present within RBCs, a “Maltese cross” pattern is seen. Treatment is with azithromycin and atovaquone in mild cases, or quinine and clindamycin in severe cases.
(A) Plasmodium falciparum causes malaria and should be considered since it also infects RBCs and produces fever and hemolytic anemia. (B) Strongyloides is a nematode and one of the most common parasitic infections worldwide. Infection occurs within the small intestine and can cause intestinal obstruction requiring surgery. (C) Clonorchis sinensis is a liver fluke that resides in the biliary tract and can cause obstructive jaundice; however, it does not produce intraerythrocytic inclusions. (D) Echinococcus granulosus is a tapeworm that typically causes disease of the lung and liver. It can cause liver cysts, which should not be biopsied (if possible) given the risk of a subsequent anaphylactic reaction. Ehrlichiosis is also a tick-borne infection but is caused by gram-negative bacteria and does not cause RBC inclusions. Borrelia burgdorferi is a spirochete that causes Lyme disease, which manifests acutely with a flu-like illness and erythema migrans. Rickettsia rickettsii causes Rocky Mountain spotted fever, but this patient does not have a rash.
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