USMLE Step 1 Practice Questions
Study online at https://quizlet.com/_6wzdrr
1. A 38-year-old man Toxoplasma Gondii
presents to the emer- Occurs in patients with HIV whose CD4 count is <100 cells/μL. It most
gency department commonly manifests with encephalitis characterized by seizures and/or focal
due to seizures that neurologic deficits. The classic picture on a CT scan or an MRI of the head is a
started earlier that ring-enhancing lesion with surrounding edema and mass effect (as shown in
day, as reported by this MRI). The specific visual field defect in this patient is due to the cerebral
his sister. He adds lesions causing a focal neurologic deficit.
that his vision is New-onset seizures in an HIV-positive patient with a CD4 count <100 cells/µL
also blurry. The pa- is highly suggestive of toxoplasmosis. Other manifestations are chorioretini-
tient says he has nev- tis, which is characterized by eye pain and decreased visual acuity, as seen in
er traveled outside this patient.
of the United States.
Physical examination
reveals several en-
larged cervical lymph
nodes as well as
a right homonymous
hemianopia. Labora-
tory studies show a
CD4 count of 78
cells/μL. The patient
is sent for an MRI
with ring-enhancing
lesion.
2. A 34-year-old man Inhibition of Folate Synthesis
presents to the emer- This patient presents with fever, dyspnea on exertion, and unintentional
gency department weight loss, which are suggestive of pneumonia. He also has a history of
with a dry cough, unprotected sex with multiple partners, and presents with oral thrush and
low-grade fevers, and inguinal lymphadenopathy, which are suggestive of HIV. Taken together, the
difficulty breathing patient's presentation and history raise suspicion of an opportunistic infec-
that becomes pro- tion, such as Pneumocystis jirovecii (PCP) pneumonia. PCP pneumonia is an
1/5
, USMLE Step 1 Practice Questions
Study online at https://quizlet.com/_6wzdrr
gressively worse with AIDS-defining illness and is typically seen in patients with CD4 counts <200
exertion. He says that cells/mm. P. jirovecii is an ascomycetous fungi that also causes pneumonia
he has had these in hematopoietic-cell and solid-organ transplant recipients, cancer patients,
symptoms for the and patients receiving glucocorticoids, chemotherapeutic agents, and other
past 2-3 weeks. He re- immunosuppressive medications. The standard treatment for this illness is
ports feeling increas- trimethoprim-sulfamethoxazole (TMP-SMX), a combination antibiotic that
ingly fatigued and synergistically inhibits folate synthesis by inhibiting dihydrofolate reductase
has had an uninten- and dihydropteroate synthetase. If the patient has a sulfa-drug allergy, the
tional weight loss of treatment of choice would be pentamidine.
10 pounds (4.5 kilo-
grams) in the same
time period. The pa-
tient denies any alco-
hol, tobacco, or illicit
drug use but admits
to having had mul-
tiple sexual partners
without using pro-
tection. The patient's
temperature is 38.1oC
(100.6oF), blood pres-
sure is 102/72 mm Hg,
pulse is 96/min, respi-
ratory rate is 22/min,
and SpO2 is 86% on
room air. Physical ex-
amination shows oral
thrush, bilateral rales
at the lung bases,
and right axillary
and left inguinal lym-
phadenopathy.
2/5
Study online at https://quizlet.com/_6wzdrr
1. A 38-year-old man Toxoplasma Gondii
presents to the emer- Occurs in patients with HIV whose CD4 count is <100 cells/μL. It most
gency department commonly manifests with encephalitis characterized by seizures and/or focal
due to seizures that neurologic deficits. The classic picture on a CT scan or an MRI of the head is a
started earlier that ring-enhancing lesion with surrounding edema and mass effect (as shown in
day, as reported by this MRI). The specific visual field defect in this patient is due to the cerebral
his sister. He adds lesions causing a focal neurologic deficit.
that his vision is New-onset seizures in an HIV-positive patient with a CD4 count <100 cells/µL
also blurry. The pa- is highly suggestive of toxoplasmosis. Other manifestations are chorioretini-
tient says he has nev- tis, which is characterized by eye pain and decreased visual acuity, as seen in
er traveled outside this patient.
of the United States.
Physical examination
reveals several en-
larged cervical lymph
nodes as well as
a right homonymous
hemianopia. Labora-
tory studies show a
CD4 count of 78
cells/μL. The patient
is sent for an MRI
with ring-enhancing
lesion.
2. A 34-year-old man Inhibition of Folate Synthesis
presents to the emer- This patient presents with fever, dyspnea on exertion, and unintentional
gency department weight loss, which are suggestive of pneumonia. He also has a history of
with a dry cough, unprotected sex with multiple partners, and presents with oral thrush and
low-grade fevers, and inguinal lymphadenopathy, which are suggestive of HIV. Taken together, the
difficulty breathing patient's presentation and history raise suspicion of an opportunistic infec-
that becomes pro- tion, such as Pneumocystis jirovecii (PCP) pneumonia. PCP pneumonia is an
1/5
, USMLE Step 1 Practice Questions
Study online at https://quizlet.com/_6wzdrr
gressively worse with AIDS-defining illness and is typically seen in patients with CD4 counts <200
exertion. He says that cells/mm. P. jirovecii is an ascomycetous fungi that also causes pneumonia
he has had these in hematopoietic-cell and solid-organ transplant recipients, cancer patients,
symptoms for the and patients receiving glucocorticoids, chemotherapeutic agents, and other
past 2-3 weeks. He re- immunosuppressive medications. The standard treatment for this illness is
ports feeling increas- trimethoprim-sulfamethoxazole (TMP-SMX), a combination antibiotic that
ingly fatigued and synergistically inhibits folate synthesis by inhibiting dihydrofolate reductase
has had an uninten- and dihydropteroate synthetase. If the patient has a sulfa-drug allergy, the
tional weight loss of treatment of choice would be pentamidine.
10 pounds (4.5 kilo-
grams) in the same
time period. The pa-
tient denies any alco-
hol, tobacco, or illicit
drug use but admits
to having had mul-
tiple sexual partners
without using pro-
tection. The patient's
temperature is 38.1oC
(100.6oF), blood pres-
sure is 102/72 mm Hg,
pulse is 96/min, respi-
ratory rate is 22/min,
and SpO2 is 86% on
room air. Physical ex-
amination shows oral
thrush, bilateral rales
at the lung bases,
and right axillary
and left inguinal lym-
phadenopathy.
2/5
