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USMLE STEP3 Exam
Step3 (Page 19 )

Updated On: 15-Feb-2026
Page 19 of 162
PDF with 804 Questions

A 23-year-old woman presents to your acute care clinic with a complaint of fever, sore throat, and malaise of sudden onset. Her prior medical history is significant for schizophrenia. Her vitals signs are:
BP 116/80, HR 112, RR 26, Temp 100.6 degrees Fahrenheit. On physical examination, her oral cavity features painful aphthous ulcers as well as swollen gums. Initial laboratory testing includes a CBC which returns with the following results:

· Leukocyte count 800/mm3
· Hgb 12.1 g/dL
· HCT 37.0%
· Platelet count 212 × 109/L
· Differential:
· Neutrophils, segmented 52%
· Neutrophils, bands 3%
· Lymphocytes 35%
· Monocytes 7%
· Eosinophils 3%
· Basophils 0%

Which of the following best describes the expected course of the patient's condition?

  1. The condition is usually self-limiting and requires no intervention.
  2. Use of G-CSF has been shown to speed recovery.
  3. Dose reduction of the offending agent often leads to resolution of symptoms.
  4. If discovered earlier, discontinuation of the offending agent would have prevented progression of the condition to its current severity.
  5. Tardive dyskinesia usually develops as a late finding.

Answer(s): B

Explanation:

This patient's presentation is consistent with agranulocytosis, which is defined by an absolute neutrophil count (ANC) of fewer than 500/mm3. ANC is defined as the percentage of the WBC count that is accounted for by segmented neutrophils and bands. In the case of this patient, the ANC is 55% of the WBC count or 440/mm3. Individuals with agranulocytosis commonly experience a sudden onset of malaise, fever, chills, and pharyngitis. They may also develop painful aphthous ulcers affecting the oropharyngeal mucosa. Suppression of the bone marrow, including agranulocytosis, is associated with the use of clozapine. The incidence approaches 1% within several months of treatment, independent of dose. Patients on clozapine should be monitored closely with weekly measurement of the CBC. Mild leukocytosis and other blood dyscrasias occur much less frequently with other antipsychotic drugs.Usually, there is a prodrome of several weeks duration in which the WBC count gradually declines. Decreasing the dose or discontinuing the offending agent does not always prevent progression to full blown agranulocytosis. Patients with druginduced neutropenia recover more quickly with the assistance of granulocyte colonystimulating factor (G-CSF). Additionally, individuals suffering from agranulocytosis frequently develop infections which require the use of antibiotic therapy. In these cases, further supportive and symptomatic care may be necessary depending on the severity of infection. Delaying or withholding intervention is inappropriate. Tardive dyskinesia is an adverse effect related to use of antipsychotic medications; it is not inherently related to agranulocytosis.



A62-year-old female with a history of a recent pulmonary embolus presents to your office for follow- up on anticoagulation treatment. She takes warfarin on a daily basis. She reports that for the last week she has noticed mild rectal bleeding and multiple bruises over the extremities with minimal trauma. She is comfortable appearing with normal vital signs and is not orthostatic. You ordered a stat CBC and PT/INR which revealed a mildly decreased Hgb at 11 g/dL and an elevated INR of 7. Which of the following would be the most appropriate intervention?

  1. subcutaneous injections of heparin
  2. oral allopurinol
  3. intravenous protamine sulfate
  4. oral vitamin E
  5. oral vitamin K

Answer(s): E

Explanation:

Warfarin acts as a vitamin K antagonist by blocking the regeneration of the reduced form of the vitamin. The result is a decrease in clotting factors II, VII, IX, and X leading to an increase in bleeding time. Warfarin toxicity can be alleviated by increasing the availability of vitamin K.



A 42 year old male admitted for pulmonary embolus was placed on heparin, dosed by a weight based protocol. However, later in the day, you receive a call from the floor nurse stating that the patient had spontaneous epistaxis and a very high aPTT. Use of which of the following would be best at this time?

  1. cimetidine
  2. heparinase
  3. clofibrate
  4. protamine sulfate
  5. vitamin K

Answer(s): D

Explanation:

Protamine sulfate is a strongly basic molecule that is thought to inhibit acidic heparin electrostatically. It may not, however, affect heparin-induced platelet aggregation. Cimetidine is an H2-antagonist that increases the anticoagulant response by an as yet unknown mechanism. Clofibrate is an agent used to reduce plasma lipid levels. Vitamin K is used to reverse the effect of warfarin. Heparinase is not used clinically.



A 64 year old woman presents with bilateral symmetric arthralgias and morning stiffness for several years. She says that she has been worked up for RA in the past. On review of her records as well as the examination you note subcutaneous nodules, positive rheumatoid factor, and radiographs of the hands that revealed joint erosions. Which of her findings has the highest positive likelihood ratio (LR) for the diagnosis of RA?

  1. morning stiffness
  2. rheumatoid nodules on examination
  3. symmetric arthralgias
  4. joint erosions of the hand on xray
  5. positive rheumatoid factor.

Answer(s): D

Explanation:

RA is primarily a clinical diagnosis. The history and physical examination are crucial to confirming the diagnosis and ruling out differential diagnosis. No one laboratory analysis can make the diagnosis, however using laboratory analysis in conjunction with a detailed history and examination can help to confirm the clinical suspicion. Some findings that may suggest RA include: morning stiffness (LR 1.9), symmetric arthralgias (LR 1.2), rheumatoid nodules (LR 3.0), positive serum rheumatoid factor (LR 8.4), and radiographic changes of hands/wrists that demonstrate erosions or hypodensity adjacent to the joints (LR
11). Rheumatoid factor is present in about 70% of patients with the diagnosis at some point in the course, however in less than 30% of patients with early RA. ANAmay be positive in 2040% of RA patients but may also be positive in many other disease states. Anti-CCP antibodies have been reported to have a sensitivity of 4070% and specificity of 95%. The presence of both RF and anti-CCP is very highly specific for the diagnosis of RA



A 58-year-old woman is concerned about her risk for osteoporosis and is seen by her general internist. Her mother was diagnosed with osteoporosis and had a hip fracture at age 84. She has no personal or family history of kidney stones or ulcer disease, and she has never had a fracture. She had a hysterectomy at age 48 and took estradiol for 2 years, but discontinued because of a fear of adverse effects. She does not have any vasomotor symptoms. She takes 1500 mg of calcium carbonate and 400 IU vitamin D daily. She is not on any other medications. On examination, she appears well developed and there is no evidence of kyphosis. ABMD test is performed that demonstrates a T score in the spine of 3.5 and in the hip of 2.8. CXR and mammogram are normal. Further evaluation demonstrates the following:



Which of the following is the most likely diagnosis?

  1. milk-alkali syndrome
  2. primary hyperparathyroidism
  3. sarcoidosis
  4. secondary hyperparathyroidism
  5. osteomalacia

Answer(s): B

Explanation:

Primary hyperparathyroidism is common in postmenopausal women and more than 80% present without any symptoms. The most common findings are bone loss, usually in association with estrogen deficiency. The elevated calcium, decreased phosphate, and increased urinary calcium are typical of this disorder. Milk-alkali syndrome is primarily historical disease occurring in patients receiving large quantities of calcium and alkali, and presenting with renal insufficiency, elevated phosphate, and alkalosis. Her normal renal function and relatively low dose of calcium exclude this entity. Familial hypocalciuric hypercalcemia is autosomal dominant and is diagnosed by a low urinary calcium clearance. The lack of renal insufficiency excludes secondary hyperparathyroidism. The normal CXR and Hgb make sarcoidosis and multiple myeloma unlikely. Postmenopausal osteoporosis and osteomalacia are excluded by the elevated calcium level.






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