| The following vignette applies to the next 2 items. The items in the set must be answered in sequential order. Once you click Proceed to Next Item, you will not be able to add or change an answer. |
A 29-year-old woman is brought to the emergency department with new-onset generalized tonic-clonic seizures. She has a history of HIV and has not been taking her medications consistently. According to her family, she has been sleepy and weak for the past 2 weeks. She has not had much of an appetite and has recently spent most of her time in bed. MRI of the head demonstrates 2 ring-enhancing focal lesions with surrounding edema in the right frontal lobe.
Item 1 of 2
Which of the following would be effective against the pathogen most likely responsible for this patient's symptoms?
Toxoplasma gondii is an obligate intracellular protozoan with a worldwide distribution. The cat is the definitive host of this protozoan, with humans infected following ingestion of food or water contaminated with cat feces (containing oocysts) or undercooked meat (containing pseudocysts). Immunocompromised individuals exposed to T gondii can develop encephalitis with multiple necrotizing brain lesions, resulting in fever, headache, altered mental status, and focal neurologic findings. In this patient with HIV who has seizures and multiple ring-enhancing lesions with mass effect, cerebral toxoplasmosis is a likely diagnosis. First-line treatment (which can be given empirically, particularly if test results are unrevealing) includes a combination of pyrimethamine and sulfadiazine (or pyrimethamine and clindamycin in case of sulfa drug hypersensitivity) along with leucovorin (folinic acid).
(Choice A) Amphotericin (with flucytosine) is used to treat cryptococcal meningitis, a well-known cause of meningitis in AIDS patients that typically manifests with nausea, vomiting, nuchal rigidity, and altered mental status. Ring-enhancing lesions are not commonly seen on imaging as cryptococcomas are rare. Amphotericin can treat invasive aspergillosis; however, central nervous system aspergillosis more classically presents as an abscess (eg, single ring-enhancing lesion), is often accompanied by pulmonary (eg, cough, dyspnea) and orbital manifestations in patients with HIV, and is primarily treated with voriconazole rather than amphotericin.
(Choice B) Ampicillin is typically used to treat Listeria infection. L monocytogenes can cause meningitis in immunosuppressed patients but does not typically form ring-enhancing lesions.
(Choice C) Ganciclovir is used in the treatment of cytomegalovirus (CMV) infection. CMV primarily causes symptomatic disease (eg, retinitis, esophagitis, pneumonia) in the immunosuppressed. Characteristic manifestations of central nervous system involvement include polyneuropathy, transverse myelitis, and encephalitis.
(Choice D) In developing countries, mycobacterial infection causes brain tuberculomas (nodular granulomatous lesions), but this would be less likely in the United States. Tuberculoma treatment typically includes 5 antitubercular drugs rather than only isoniazid and rifampin.
The differential diagnosis for this patient also includes primary central nervous system lymphoma (second most common after cerebral toxoplasmosis), primary brain tumors (eg, glioblastoma multiforme), metastatic carcinoma, and fungal or bacterial abscesses.
Educational objective:
In patients with HIV, the presence of multiple ring-enhancing lesions with mass effect is most often indicative of toxoplasmosis, followed by primary central nervous system lymphoma.