STEP3 Exam Questions and Answers | Exam-Dumps (Page: 16)

QUESTION: 76

A30-year-old female presents to your office for the evaluation of a rash on her back. It has been present and growing for about a week. Along with this rash, she has had a fever, headache, myalgias, and fatigue. Her symptoms started about a week after returning from a camping trip to New England. She denies having any bites from ticks or other insects and exposure to poison ivy and has had no wounds to her skin. On examination, her temperature is 99.5°F and her v ital signs are otherwise normal. Her rash is shown in Figure. Her examination is otherwise unremarkable.

What is the most likely cause of her rash?

contact dermatitis secondary to plant exposure
infection transmitted by tick bite
infection transmitted by mosquito bite
group A Streptococcus suprainfection of small puncture wound
allergic reaction to ingested (i.e., food) allergen

Answer(s): B

Explanation:

Lyme disease is the most common vector-borne disease in the United States. It is caused by infection with B. burgdorferi, a spirochete that is transmitted to humans through the bite of ticks of the Ixodes family. These ticks are very small, so frequently the victim is unaware of having been bitten. After an incubation of 330 days, a red macule or papule develops at the site of the bite, which expands to form a large annular lesion with partial central clearing or several red rings within an outside ring. The lesion, erythema migrans, is often said to resemble a "bull's-eye" target. Within a few days or weeks of this, the patient often complains of flu-like symptoms fever, chills, myalgias, headache, fatigue caused by the hematogenous spread of the spirochete. Lyme disease has been found in most of the United States, but is most common in the New England states, where over 20% of Ixodes ticks are infected with the spirochete. Left untreated, patients may progress to develop multiple complications, including neurologic, musculoskeletal, or cardiac involvement. Lyme disease is usually diagnosed by recognition of the symptoms and signs, along with serologic testing. However, serologic tests may be negative for several weeks after infection. IgG and IgM should be tested in acute and convalescent samples. Only 2030% of exposures will have positive acute antibody responses, whereas 7080% will have positive convalescent titers. Samples that are positive by ELISA assay should be confirmed by Western blot testing. Empirical antibiotic therapy, preferably with doxycycline, is recommended for patients with a high probability of Lyme disease--such as those with erythema migrans. Doxycycline is the preferred antibiotic for treatment of early stage Lyme disease in adults because of its effectiveness against Lyme disease and other infections, such as human granulocytic ehrlichiosis, which is also transmitted by Ixodes ticks. Waiting to treat until convalescent titers become positive would not be recommended in this patient, who has a high likelihood of having Lyme disease, as it may result in more complications developing and the need for longer and more intensive treatment. For more advanced stages of disease, such as the presence of nervous system involvement or third-degree heart block, parenteral antibiotic treatment is necessary. Ceftriaxone is the treatment of choice in this setting.

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QUESTION: 77

A30-year-old female presents to your office for the evaluation of a rash on her back. It has been present and growing for about a week. Along with this rash, she has had a fever, headache, myalgias, and fatigue. Her symptoms started about a week after returning from a camping trip to New England. She denies having any bites from ticks or other insects and exposure to poison ivy and has had no wounds to her skin. On examination, her temperature is 99.5°F and her v ital signs are otherwise normal. Her rash is shown in Figure. Her examination is otherwise unremarkable.

You order IgM and IgG ELISA testing for Borrelia burgdorferi and the results return as negative. Which of the following management options would be most appropriate?

Treat the patient with a topical steroid for presumed contact dermatitis.
Treat the patient with oral steroids for a presumed systemic allergic reaction.
Treat the patient with oral cephalexin for streptococcal cellulitis.
Treat the patient with doxycycline for Lyme disease.
No medication at present, but have the patient return in 68 weeks for repeat serologic testing and treat for Lyme disease if positive at that time.

Answer(s): D

Explanation:

Lyme disease is the most common vector-borne disease in the United States. It is caused by infection with B. burgdorferi, a spirochete that is transmitted to humans through the bite of ticks of the Ixodes family. These ticks are very small, so frequently the victim is unaware of having been bitten. After an incubation of 330 days, a red macule or papule develops at the site of the bite, which expands to form a large annular lesion with partial central clearing or several red rings within an outside ring. The lesion, erythema migrans, is often said to resemble a "bull's-eye" target. Within a few days or weeks of this, the patient often complains of flu-like symptoms fever, chills, myalgias, headache, fatigue caused by the hematogenous spread of the spirochete. Lyme disease has been found in most of the United States, but is most common in the New England states, where over 20% of Ixodes ticks are infected with the spirochete. Left untreated, patients may progress to develop multiple complications, including neurologic, musculoskeletal, or cardiac involvement. Lyme disease is usually diagnosed by recognition of the symptoms and signs, along with serologic testing. However, serologic tests may be negative for several weeks after infection. IgG and IgM should be tested in acute and convalescent samples. Only 2030% of exposures will have positive acute antibody responses, whereas 7080% will have positive convalescent titers. Samples that are positive by ELISA assay should be confirmed by Western blot testing. Empirical antibiotic therapy, preferably with doxycycline, is recommended for patients with a high probability of Lyme disease--such as those with erythema migrans. Doxycycline is the preferred antibiotic for treatment of early stage Lyme disease in adults because of its effectiveness against Lyme disease and other infections, such as human granulocytic ehrlichiosis, which is also transmitted by Ixodes ticks. Waiting to treat until convalescent titers become positive would not be recommended in this patient, who has a high likelihood of having Lyme disease, as it may result in more complications developing and the need for longer and more intensive treatment. For more advanced stages of disease, such as the presence of nervous system involvement or third-degree heart block, parenteral antibiotic treatment is necessary. Ceftriaxone is the treatment of choice in this setting.

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QUESTION: 78

A 39-year-old HIV-positive male presents for routine follow-up. He is on highly active antiretroviral therapy. A CD4 count is 250/L. His vital signs are within normal limits and his examination is normal. Which of the following management options is most appropriate at this time?

Continue with current regiment without change.
Add azithromycin for Mycobacterium avium complex prophylaxis.
Add TMP-SMZ (Bactrim DS) for Pneumocystis carinii prophylaxis.
Test the patient for IgG antibody to Toxoplasma gondii if such a test has not yet been done.
Start ganciclovir for CMV prophylaxis.

Answer(s): D

Explanation:

Guidelines for the prevention of opportunistic infections in persons with HIV recommend institution of TMP- SMZ for P. carinii pneumonia prophylaxis when the CD4 count falls below 200 cells/L. Azithromycin or clarithromycin are recommended for M. avium complex when the CD4 count falls below 50 cells/L. All HIV- infected individuals should be tested for IgG antibody against T. gondii as soon as possible after being diagnosed with HIV infection. Counselling should also be provided regarding avoidance of exposure to sources of Toxoplasma. Ganciclovir would be recommended for CMV prophylaxis if there were a history of prior end-organ disease. In a patient with HIV, a PPD is considered positive if there is 5 mm of induration. In a patient with a normal CXR, no symptoms of active disease and no history of treatment for a prior positive PPD, the recommended treatment would be isoniazid for 9 months. In the absence of a suspicious appearing CXR or symptoms, AFB testing would be unnecessary. A booster test would also be unnecessary, as the initial test is already positive. Multidrug therapy would be indicated only for confirmed or suspected active tuberculosis.

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QUESTION: 79

A 39-year-old HIV-positive male presents for routine follow-up. He is on highly active antiretroviral therapy. A CD4 count is 250/L. His vital signs are within normal limits and his examination is normal. He has a PPD placed and follows up in 48 hours. At the site of the injection you find 6 mm of induration. A CXR is normal. He has never been treated for tuberculosis or a positive PPD before.
Which management option is most appropriate?

Collect sputum samples for 3 days to send for AFB (acid fast bacilli) staining.
Empirically start four-drug therapy for active tuberculosis.
Empirically start isoniazid daily for 9 months.
Have the patient return in 1 week for a second PPD to assess for the presence of a "booster" phenomenon; treat with isoniazid if 10 mm induration.
No intervention at this time but repeat the test in 6 months.

Answer(s): C

Explanation:

Guidelines for the prevention of opportunistic infections in persons with HIV recommend institution of TMP- SMZ for P. carinii pneumonia prophylaxis when the CD4 count falls below 200 cells/L. Azithromycin or clarithromycin are recommended for M. avium complex when the CD4 count falls below 50 cells/L. All HIV- infected individuals should be tested for IgG antibody against T. gondii as soon as possible after being diagnosed with HIV infection. Counselling should also be provided regarding avoidance of exposure to sources of Toxoplasma. Ganciclovir would be recommended for CMV prophylaxis if there were a history of prior end-organ disease. In a patient with HIV, a PPD is considered positive if there is 5 mm of induration. In a patient with a normal CXR, no symptoms of active disease and no history of treatment for a prior positive PPD, the recommended treatment would be isoniazid for 9 months. In the absence of a suspicious appearing CXR or symptoms, AFB testing would be unnecessary. A booster test would also be unnecessary, as the initial test is already positive. Multidrug therapy would be indicated only for confirmed or suspected active tuberculosis.

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QUESTION: 80

A 39-year-old HIV-positive male presents for routine follow-up. He is on highly active antiretroviral therapy. A CD4 count is 250/L. His vital signs are within normal limits and his examination is normal. One month later, a repeat measurement of the patient's CD4 count is 225/L. Which of the following interventions would be the most appropriate at this time?

Continue the current regimen without change.
Modify the patient's antiretroviral therapy to prevent development of resistance.
Discontinue any prophylactic medications that the patient is taking.
Begin azithromycin for M. avium complex prophylaxis.
Recheck CD4 count due to suspected laboratory error.

Answer(s): A

Explanation:

Guidelines for the prevention of opportunistic infections in persons with HIV recommend institution of TMP- SMZ for P. carinii pneumonia prophylaxis when the CD4 count falls below 200 cells/L. Azithromycin or clarithromycin are recommended for M. avium complex when the CD4 count falls below 50 cells/L. All HIV- infected individuals should be tested for IgG antibody against T. gondii as soon as possible after being diagnosed with HIV infection. Counselling should also be provided regarding avoidance of exposure to sources of Toxoplasma. Ganciclovir would be recommended for CMV prophylaxis if there were a history of prior end-organ disease. In a patient with HIV, a PPD is considered positive if there is 5 mm of induration. In a patient with a normal CXR, no symptoms of active disease and no history of treatment for a prior positive PPD, the recommended treatment would be isoniazid for 9 months. In the absence of a suspicious appearing CXR or symptoms, AFB testing would be unnecessary. A booster test would also be unnecessary, as the initial test is already positive. Multidrug therapy would be indicated only for confirmed or suspected active tuberculosis.

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USMLE STEP3 Exam (page: 16) USMLE Step3 Updated on: 15-Feb-2026

QUESTION: 76

Explanation:

QUESTION: 77

Explanation:

QUESTION: 78

Explanation:

QUESTION: 79

Explanation:

QUESTION: 80

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USMLE STEP3 Exam (page: 16)
USMLE Step3
Updated on: 15-Feb-2026