A 34-year-old man presents to the emergency department with a dry cough, low-grade fevers, and difficulty breathing that becomes progressively worse with exertion. He says that he has had these symptoms for the past 2-3 weeks. He reports feeling increasingly fatigued and has had an unintentional we...
USMLE
A 34-year-old man presents to the emergency department with a dry cough, low-grade
fevers, and difficulty breathing that becomes progressively worse with exertion. He says
that he has had these symptoms for the past 2-3 weeks. He reports feeling increasingly
fatigued and has had an unintentional weight loss of 10 pounds (4.5 kilograms) in the
same time period. The patient denies any alcohol, tobacco, or illicit drug use but admits
to having had multiple sexual partners without using protection. The patient's
temperature is 38.1oC (100.6oF), blood pressure is 102/72 mm Hg, pulse is 96/min,
respiratory rate is 22/min, and SpO2 is 86% on room air. Physical examination shows
oral thrush, bilateral rales at the lung bases, and right axillary and left inguinal
lymphadenopathy. correct answers Inhibition of Folate Synthesis
This patient presents with fever, dyspnea on exertion, and unintentional weight loss,
which are suggestive of pneumonia. He also has a history of unprotected sex with
multiple partners, and presents with oral thrush and inguinal lymphadenopathy, which
are suggestive of HIV. Taken together, the patient's presentation and history raise
suspicion of an opportunistic infection, such as Pneumocystis jirovecii (PCP)
pneumonia. PCP pneumonia is an AIDS-defining illness and is typically seen in patients
with CD4 counts <200 cells/mm. P. jirovecii is an ascomycetous fungi that also causes
pneumonia in hematopoietic-cell and solid-organ transplant recipients, cancer patients,
and patients receiving glucocorticoids, chemotherapeutic agents, and other
immunosuppressive medications. The standard treatment for this illness is trimethoprim-
sulfamethoxazole (TMP-SMX), a combination antibiotic that synergistically inhibits folate
synthesis by inhibiting dihydrofolate reductase and dihydropteroate synthetase. If the
patient has a sulfa-drug allergy, the treatment of choice would be pentamidine.
A 38-year-old man presents to the emergency department due to seizures that started
earlier that day, as reported by his sister. He adds that his vision is also blurry. The
patient says he has never traveled outside of the United States. Physical examination
reveals several enlarged cervical lymph nodes as well as a right homonymous
hemianopia. Laboratory studies show a CD4 count of 78 cells/μL. The patient is sent for
an MRI with ring-enhancing lesion. correct answers Toxoplasma Gondii
Occurs in patients with HIV whose CD4 count is <100 cells/μL. It most commonly
manifests with encephalitis characterized by seizures and/or focal neurologic deficits.
The classic picture on a CT scan or an MRI of the head is a ring-enhancing lesion with
surrounding edema and mass effect (as shown in this MRI). The specific visual field
defect in this patient is due to the cerebral lesions causing a focal neurologic deficit.
New-onset seizures in an HIV-positive patient with a CD4 count <100 cells/µL is highly
suggestive of toxoplasmosis. Other manifestations are chorioretinitis, which is
characterized by eye pain and decreased visual acuity, as seen in this patient.
A 40-year-old woman presents to the physician with a 10-month history of progressive
hearing loss, dizziness, and impaired balance. Past medical history is unremarkable.
Neurologic exam reveals decreased hearing bilaterally. Dix-Hallpike maneuver does not
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