USMLE USMLE-STEP-3 Online Practice Questions and Exam Preparation

USMLE USMLE-STEP-3 Online Questions & Answers

• Question 411:

  A severely traumatized patient who has been receiving prolonged parenteral alimentation develops diarrhea, mental status changes, alopecia, and perioral and periorbital dermatitis. Administration of which of the following trace element is most likely to reverse these complications?

  A. iodine
  B. zinc
  C. selenium
  D. silicon
  E. tin
  B. zinc

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  Explanation

  Symptoms of zinc deficiency include diarrhea, mental status changes, alopecia, and periorbital, perinasal, and perioral dermatitis. Persons who have cirrhosis, who are receiving steroids, who have excessive loss of GI secretions, or who are severely traumatized are at risk for zinc deficiency. Deficiency states resulting from inadequate ingestion of selenium, silicon, and tin have not been described. Deficiency of iodine produces hypothyroidism.

• Question 412:

  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 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?

  A. Treat the patient with a topical steroid for presumed contact dermatitis.
  B. Treat the patient with oral steroids for a presumed systemic allergic reaction.
  C. Treat the patient with oral cephalexin for streptococcal cellulitis.
  D. Treat the patient with doxycycline for Lyme disease.
  E. 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.
  D. Treat the patient with doxycycline for Lyme disease.

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  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.

• Question 413:

  A 31/2-year-old female presented with a left upper quadrant abdominal mass. The child had no previous history of medical illnesses. An ultrasound examination revealed a markedly deformed left kidney with 12 cm nonhomogenous soft tissue mass arising from the upper pole. Medial displacement of the bowel loops was also noted.

  What would be the most likely diagnosis in this case?

  A. hydronephrotic kidney
  B. Wilms tumor
  C. tuberculosis
  D. congenital malformation
  E. papillary transitional cell carcinoma of the renal pelvis
  B. Wilms tumor

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  Explanation

  Wilms tumor is the most common primary renal tumor in childhood, usually diagnosed between the ages of 2 and 5. The risk of Wilms tumor is increased in association with at least three recognizable groups of congenital malformations exhibiting alteration in at least two distinct chromosomal loci. A few familial cases of Wilms tumor not associated with identifiable lesions or mutations involving either the WT-1 or the WT-2 gene suggest that there may be another locus that plays a role in some tumors, but that still remains unknown. Wilms tumor presents as a large solitary mass and in 10% of cases may be bilateral. Microscopically, the Wilms tumor is characterized by recognizable attempts to recapitulate different stages of nephrogenesis. The classic triphasic combination of blastemic, stromal, and epithelial cell types is observed in the majority of the lesions. Occasional skeletal muscle differentiation can be seen, as well as squamous, mucinous epithelium, cartilage, or bone. The combined therapy of chemo, radiation, and surgery has dramatically improved the results of long-term survival in these patients, up to 90%

• Question 414:

  A 40-year-old male is returning to the office for a follow-up visit. He is told about his blood work results, which are consistent with leukemia. He is informed that he should receive a bone marrow biopsy for further clarification. While being presented with this information, he remains silent, peering, and staring intensely. When finished, he comments, "Doctors think they are so smart!" He then explains that he has been mistreated by physicians in the past and, in fact, has several malpractice suits pending. He feels that the biopsy was recommended only "because you want to use me in order to publish and further your career."

  When interacting with this patient, which of the following approaches would be most effective?

  A. defend the recommendation by citing professional credentials
  B. encourage him to speak with a psychiatrist to provide added support
  C. interpret his anger as a defense against his fears of having leukemia
  D. provide detailed information regarding his differential diagnosis
  E. refer him to a colleague to avoid litigation
  D. provide detailed information regarding his differential diagnosis

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  Explanation

  This patient clearly presents with a paranoid stance, although he is not overtly psychotic. Individuals with antisocial personality disorder are usually more dishonest, aggressive, and exploitative in their attitudes. Narcissistic patients may become easily offended by interactions when not feeling as though they are being treated as "special," but they do not display as much overt mistrust. Patients with schizoid and schizotypal personality disorders appear indifferent or odd, usually with a detached attitude.

  Patients with paranoid personality disorder display a pervasive suspiciousness toward others, continuously feeling slighted and bearing grudges, not unusually in the form of litigiousness

• Question 415:

  A 30-year-old male is brought to the ED after being hit in the head by a baseball. He is making incomprehensible sounds, but no words. He opens his eyes and withdraws to painful stimuli. His Glasgow Coma Scale score is:

  A. 10
  B. 9
  C. 8
  D. 7
  E. 6
  C. 8

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  Explanation

  The Glasgow Coma Scale is used to quantify a neurologic examination in patients with a head injury. It is based on three elements: eye opening, motor response, and verbal response. The total score ranges from 3 (worst) to 15 (best) with a score of 8 or lower indicating a coma. The scale is shown below. This patient has a score of 2E. + 4(M) + 2(V) = 8. This patient has evidence of a severe head injury. The initial step should be to protect his airway and prevent hypoxia, which could adversely affect his head injury. Thus, the initial step should be endotracheal intubation. Neurosurgical expertise, imaging to define the injury, and screens to rule out drugs or alcohol as contributions are all important, but should be performed after airway, breathing, and circulation are addressed. Mannitol is indicated in patients with evidence of herniation, such as those with pupillary dilatation.

  

• Question 416:

  In your role as a physician in a community health center, you agree to perform sports preparticipation examinations on students from the local high school. You have several scheduled for today. Your first appointment is with a 16-year-old male who is planning to run on the cross-country team in the Fall and play baseball in the Spring. He reports that one time he "blacked out" while running, but he has never had chest pain while exercising and he is one of the top runners on the team. He has no known medical history, denies alcohol, tobacco, recreational drug, or performance-enhancing drug use. He has a cousin who died at the age of 21 of "some kind of heart disease," although your patient is not sure of any details. On examination, he is healthy appearing and has normal vital signs, with a pulse rate of 72 and a blood pressure of 100/65. Auscultation of his heart reveals no cardiac murmur while he is lying down, a soft systolic murmur when he stands which increases on having the patient perform a Valsalva maneuver. The remainder of his examination is normal.

  At this point, what is your most appropriate management option?

  A. allow unrestricted participation in sports
  B. allow participation in noncontact sports
  C. allow him to play baseball but not run cross-country
  D. restrict him from all athletic participation until he is evaluated by a cardiologist
  E. restrict him from competitive athletics but allow him to participate in gym class
  D. restrict him from all athletic participation until he is evaluated by a cardiologist

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  Explanation

  Explanations:

  Primary care physicians are frequently called on to perform preparticipation examinations on young athletes. These types of encounters can be used to serve a number of purposes, including attempting to identify conditions that may adversely affect the athlete during participation, identify conditions that may predispose the athlete to injury, provide anticipatory guidance on high-risk behaviors common to the age group being addressed, and fulfill legal conditions of the institution involved. Fortunately, the rate of sudden death in young athletes is low.

  In those under the age of 35, the most common cause of sudden death is congenital cardiac anomalies. Hypertrophic cardiomyopathy (HCM) is responsible for about onethird of these deaths. Unfortunately, sudden death may be the presenting symptom of HCM. Apersonal or family history of congenital heart disease, symptoms of chest pain or tightness, palpitations, dyspnea, syncope or near-syncope are important. A family history of HCM or unexplained sudden death in someone under the age of 50 is significant as well. The murmur of HCM may not be present in all persons with this disorder.

  To identify the murmur, dynamic auscultation is often necessary. The heart should be auscultated while the patient is lying and then standing. As this murmur is accentuated by maneuvers which reduce cardiac preload, the murmur will get louder when the patient stands or performs a Valsalva maneuver and will diminish as the patient lies or squats. As the patient has the concerning historical point of exertional syncope and a family history of an unexplained, early death along with a characteristic murmur on examination, further evaluation is warranted. In the 26th Bethesda Conference report, the American College of Cardiology recommends that persons with HCM should be restricted from all, except possibly for the least strenuous, athletic activity. In this case, restriction of all athletic activity until the patient can be further evaluated by a cardiologist--preferably one with experience in dealing with the evaluation of athletes--would be the most appropriate option of the choices given.

  Marfan syndrome is a connective tissue disorder that typically affects the eyes, skeletal system, and cardiovascular system. Persons with Marfan syndrome are typically tall and have arm spans that are greater than their height. Signs include long, slender digits, high-arched palates, and pectus deformities of the chest. Lens dislocations in the eye are common. Detecting Marfan syndrome during a preparticipation examination is important because of the occurrence of aortic\ root dilation and the risk of sudden death caused by aortic rupture. The patient has multiple signs of Marfan syndrome and further evaluation would be indicated. Of the options given, an echocardiogram to evaluate the aortic root and to look for other valvular abnormalities would be indicated. These persons usually require referral to an ophthalmologist as well for a dilated eye examination to evaluate for lens dislocations. Turner syndrome is a syndrome of gonadal dysgenesis, associated with a 45, X karyotype (or another defect of the X chromosome). This syndrome is typically associated with a short stature and multiple anomalies including a webbed neck and "shield" chest. The female athlete triad is a syndrome of disordered eating, amenorrhea, and osteoporosis. It is seen most often in participants in activities that emphasize low body weights, such as gymnastics or ballet. The presence of regular menstrual cycles makes this diagnosis unlikely. Atlantoaxial instability can be associated with Down syndrome.

  Physicians performing preparticipation examinations on someone with Down syndrome must consider performing lateral cervical spine x-rays with flexion and extension views. This patient does not have any of the classic findings of Down syndrome. Similarly, she does not exhibit any of the classic symptoms of type 1 diabetes polydipsia, polyphagia, and polyuria. Performing serum glucose testing would therefore not be indicated. The patient is the most typical type of patient who presents for a preparticipation examination-- the healthy adolescent. This may be the only encounter that a physician will have with an adolescent, especially an adolescent male. It is in this population where a physician can use this encounter to address other age appropriate health maintenance issues. As the patient had a Td booster 3 years ago, another one at this point would not be indicated (although consideration could be given to providing a Tdap). Other vaccinations to consider would be hepatitis B and MMR, if he has not previously been adequately immunized. As he has had two MMR vaccines, he has completed the recommended series. There is no history given regarding hepatitis B vaccination and this would be something to address clinically. A nonjudgmental discussion of sexual behaviors, drug use, alcohol use, and other high-risk behaviors would also be appropriate. Screening athletes who have neither concerning symptoms nor signs with ECGs is not recommended because of the poor predictive values and significant costs involved with mass screening. ECGs should be performed without hesitation in any athlete who has a history, examination finding, or preexisting diagnosis of a potentially high-risk condition. Although some localities may require a urinalysis as part of a preparticipation examination, there is no evidence to recommend universal screening.

• Question 417:

  A 30-year-old (G2P0101) female presents to the clinic for a new obstetric visit. She has an unknown LMP. She reports that she discovered she was pregnant when she took a urine pregnancy test at home a month ago. She vaguely recalls having a period about 2 months ago, but is not sure exactly when that occurred. She reports that she is generally healthy. She had a previous delivery at 36 weeks EGA, though she reports her doctor was not really sure about her due date in that pregnancy. She reports that she had a normal spontaneous vaginal delivery in her previous pregnancy, and the child is healthy. Her postpartum course was complicated by depression, which has since resolved and not recurred. She denies history of sexually transmitted diseases or abnormal pap smears. She has no surgical history. She does not smoke, drink alcohol, or use illicit drugs. She does not have any family history of hypertension, diabetes, twins, or congenital anomalies. She does report that her mother has a history of depression

  Given the patient's history of postpartum depression as well as her family history of depression, her risk of postpartum depression after this pregnancy is approximately what percentage?

  A. 50% or greater
  B. 5%
  C. 10%
  D. 20%
  E. less than 1%
  A. 50% or greater

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  Explanation

  The pelvic ultrasound is the most reliable measurement of fetal gestational age in the absence of accurate dating by LMP. A first trimester sonogram is thought to be reliable ? days. Given the patient's history, she is likely at least 2 months pregnant. hCG level at this gestation can be variable and is not a useful method of pregnancy dating. A pelvic examination is useful to help confirm likely dating, but is not a reliable means of determining EDD. FSH and LH levels have no role in determining pregnancy dating.

  The risk of postpartum major depression is estimated at 820% in all postpartum patients. In those with a previous history of postpartum depression, the risk is thought to be 50100%. In patients who have had previous depression not associated with pregnancy, the risk of postpartum depression is 2030%. Maternity blues is a milder psychological reaction that can occur in the early postpartum period and is thought to occur in 70+ % of all postpartum patients. Patients with a history of bipolar disease have a igher risk of recurrence in the postpartum period, and these patients often present with postpartum psychosis symptoms.

• Question 418:

  A 72-year-old diabetic is transferred to your hospital for fever and altered mental status in the late summer. Symptoms started in this patient 1 week prior to admission. On physical examination, the patient was disoriented. There were no focal neurologic findings. There was a fine rash on the patient's trunk. On oral examination, there were tongue fasciculations. A lumbar puncture was performed which showed a glucose of 71 and a protein of 94; microscopy of the cerebrospinal fluid (CSF) revealed 9 RBC and 14 WBC (21 P, 68 L, 11 H). The creatinine phosphokinase was 506. An electroencephalogram and MRI of the brain were normal. What is the best interpretation of these findings?

  A. The patient may have cryptococcal meningitis.
  B. The patient may have disseminated candidiasis.
  C. The patient may have West Nile virus.
  D. The patient may have Coccidioides immitis infection.
  E. The patient may have rhinocerebral mucormycosis.
  C. The patient may have West Nile virus.

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  Explanation

  This is a clinical presentation of West Nile virus infection. The tongue fasciculations go along with an inflammation at the base of the brain. The patient is at the right age for West Nile virus infection and he is immunocompromised due to diabetes. The diagnosis can be made by performing a West Nile virus IgM titer on the CSF. Diabetics can have cryptococcal meningitis. Lumbar puncture in this setting is usually normal with increased opening pressure, and rhabdomyolysis is not a feature of this disease.

  Diabetics are more at risk for candidiasis. However, the patient has no history of instrumentation, IV catheters, or other situations that would lead to disseminated candidiasis. Diabetics are at increased risk for C. immitis infection, but we have no history of the patient living in an area endemic for this organism. Diabetics are at increased risk for rhinocerebral mucormycosis. An MRI of the head might have shown involvement of the sinus. However, this patient's presentation is not consistent with rhinocerebral mucormycosis.

• Question 419:

  A 67-year-old female was admitted to the hospital because of chronic fatigue and low back pain. An x- ray of the vertebral column showed diffuse osteoporosis and compression fractures of L1 and L2 vertebral bodies. The complete blood count (CBC) was within normal limits. The peripheral blood smear showed rouleaux formation. The immunoelectrophoresis showed a monoclonal spike of more than 3 g. A bone marrow biopsy was performed and showed an increase of more than 20% in plasma cells see Figure below

  

  Radiographs of the bone and skeletal system in multiple myeloma will more characteristically show which of the following?

  A. fractures
  B. osteoblastic lesions
  C. destructive bone lesions throughout the skeletal system
  D. the skeletal system will remain intact
  E. changes that resemble Paget disease
  C. destructive bone lesions throughout the skeletal system

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  Explanation

  Multiple myeloma is a plasma cell dyscrasia that is characterized by involvement of the skeleton in multiple sites. The characteristic x-ray shows punched-out bone lesions that are very easily seen in the calvarium. Extension of the disease to lymph nodes and extranodal sites, such as skin, can be seen. The bone marrow biopsy and smears reveal an increased number of plasma cells, which usually constitute greater than 20% of all of the cells. The cells either diffusely infiltrate and replace the marrow elements or can be seen scattered throughout the hematopoietic elements. The neoplastic plasma cells have a perinuclear hof and an eccentrically placed nucleus which allows the recognition. In 99% of patients with multiple myeloma, electrophoretic analysis reveals increased levels of IgG in the blood, light chains (Bence-Jones proteins) in the urine, or both. The monoclonal IgG produces a high spike when seen in the serum or in the urine, subject to electrophoresis. In general, the quantitative analysis of the monoclonal IgG is more than 3 g. The clinicopathologic diagnosis of multiple myeloma rests on radiographic and laboratory findings. Marrow examination may reveal increased plasma cells or sheet- like aggregates that may completely replace the normal elements. The prognosis for this condition is variable, but generally poor.

• Question 420:

  A 40-year-old woman presents with nausea, vomiting, and weakness. She has been amenorrheic since the birth of her last child 1 year ago and has not felt well since that time. On examination, she appears chronically ill, her thyroid is not palpable, and there is no galactorrhea. Laboratory studies on admission include:

  

  The most appropriate next step is to start treatment with which of the following?

  A. hydrocortisone
  B. fluid restriction
  C. desmopressin
  D. glucagon
  E. fludrocortisone
  A. hydrocortisone

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  Explanation

  The patient has Sheehan syndrome, necrosis of the pituitary associated with childbirth. She has panhypopituitarism, but the most urgent hormone to replace is hydrocortisone. Thyroid hormone should not be replaced until after glucocorticoids are administered. The hyponatremia will correct with glucocorticoids and saline. The patient is not deficient in mineralocorticoids, as she does not have primary adrenal insufficiency; therefore, fludrocortisone is not indicated.