USMLE USMLE Certifications USMLE-STEP-3 Questions & Answers

• Question 451:

  On a Monday morning you see a 12-year-old otherwise healthy boy in the emergency department. The parents brought the boy in because they noticed that he started to have an abnormal gait in the past few days. He seems to be shuffling his feet. The boy complains that his legs feel heavy and are tingling. He relates that his arms feel fine. His past history is significant for attention deficit/hyperactivity disorder (ADHD) for which he is taking methylphenidate. He denies trauma or taking any other medicines or drugs. On examination, he is afebrile with normal vital signs. His entire physical examination is normal with the exception of the examination of is lower extremities. He has 3/5 strength throughout both of his lower extremities with a normal muscle mass. His all joints have a full range of motion, without any pain or swelling. His reflexes are absent and he describes some paresthesias of his feet and ankles.

  What is the most likely diagnosis?

  A. methylphenidate toxicity

  B. acute inflammatory demyelinating polyneuropathy (Guillain-Barré syndrome)

  C. acute poliomyelitis

  D. malingering (school avoidance)

  E. polymyositis

  Correct Answer: B Section: (none)

  Explanation:

  Acute inflammatory demyelinating polyneuropathy, commonly called Guillain-Barré syndrome, is an ascending paralysis with a hallmark of absent reflexes. There may also be some nominal sensory deficits as well, but they are not as striking as the paresis. Methylphenidate toxicity usually results in seizures and tachycardia. In children with malingering, reflexes are usually present, as they are not under cognitive control. Reflexes are also present in children with polymyositis. Children with polymyositis will usually have fever and muscle pain with weakness, as well. With the use of the polio vaccines (OPV or IPV), poliomyelitis is no longer present in wild type in the United States. Guillain-Barré is usually a self-limited disease. The most common complication is respiratory failure. The paresis usually advances for 4872 hours and then will slowly recede. The use of corticosteroids is not recommended. Plasmaphoresis is used in the following situations: progressive paresis, nonambulatory patients, or bulbar or respiratory involvement. As this child's disease has plateaued at the time of evaluation, plasmaphoresis would be of little benefit.

• Question 452:

  An 8-year-old male presents to your office complaining of a 1-week history of painful knee and elbow joints. On examination, you find a painful, hot, and swollen knee. He also has multiple erythematous macules with pale centers on his trunk and extremities. The laboratory work you order reveals elevated antistreptococcal antibodies.

  Which of the following information is required to make this diagnosis?

  A. The child must currently have a fever.

  B. The child must have arthritis.

  C. The presence of a group A streptococcal (GAS) infection must be documented.

  D. The child may have chorea alone.

  E. Aspiration of fluid from the swollen knee is required to confirm the diagnosis.

  Correct Answer: D Section: (none)

  Explanation:

  ARF is clinically diagnosed by using the Jones criteria. The Jones criteria are separated into major and minor findings. The major criteria are arthritis (not simply arthralgia), carditis, Sydenham chorea, erythema marginatum, and subcutaneous nodules. The minor criteria include the presence of a fever, arthralgias, documentation of a GAS infection (either currently or in the past), or laboratory evidence of inflammation (increased ESR). Two major criteria, or one major and two minors, are required for the diagnosis of ARF. The only exception to this rule is that the presence of Sydenham chorea alone will make the diagnosis. While the documentation of a prior, or current, GAS infection is compelling, it is not a requirement for the diagnosis of ARF. Children with rheumatic fever are not considered contagious.

• Question 453:

  An 8-year-old male presents to your office complaining of a 1-week history of painful knee and elbow joints.

  On examination, you find a painful, hot, and swollen knee. He also has multiple erythematous macules with

  pale centers on his trunk and extremities. The laboratory work you order reveals elevated antistreptococcal

  antibodies.

  What is the most likely diagnosis?

  A. JRA

  B. septic arthritis

  C. acute rheumatic fever (ARF)

  D. child abuse

  E. SLE

  Correct Answer: C Section: (none)

  Explanation:

  ARF is clinically diagnosed by using the Jones criteria. The Jones criteria are separated into major and minor findings. The major criteria are arthritis (not simply arthralgia), carditis, Sydenham chorea, erythema marginatum, and subcutaneous nodules. The minor criteria include the presence of a fever, arthralgias, documentation of a GAS infection (either currently or in the past), or laboratory evidence of inflammation (increased ESR). Two major criteria, or one major and two minors, are required for the diagnosis of ARF. The only exception to this rule is that the presence of Sydenham chorea alone will make the diagnosis. While the documentation of a prior, or current, GAS infection is compelling, it is not a requirement for the diagnosis of ARF. Children with rheumatic fever are not considered contagious.

• Question 454:

  You see a 2-month-old infant in the emergency department for vomiting. The mother says that the baby has been spitting up more over the past few days and has become more irritable. She denies any fever, diarrhea, or change in formula. The mother tells you that there is a family history of "heartburn" and that her other children have all spit up. The infant has some emesis in the emergency department that seems to be formula mixed with some bile. The infant is intermittently irritable and sleepy.

  Which of the following would be the most appropriate initial test?

  A. abdominal computed tomography (CT)

  B. barium enema

  C. abdominal ultrasound

  D. UGI series with small bowel follow through

  E. radionuclide scan

  Correct Answer: D Section: (none)

  Explanation:

  Bilious emesis in an infant is malrotation until proven otherwise. Malrotation can lead to a midgut volvulus. The volvulus can result in bowel ischemia and necrosis. This makes bilious emesis in a newborn a concerning finding. Pyloric stenosis would cause nonbilious emesis. Imperforate anus would present with the failure of stool passage. Diaphragmatic hernia will present with poor feeding, drooling, and respiratory embarrassment The best radiographic test in the diagnosis of malrotation is an UGI contrast study with small bowel follow through. This will identify the duodenum and its location relative to the ligament of Treitz. The characteristic finding in a midgut volvulus is the "corkscrew" sign, which is seen as contrast media traverses the kinked intestine. An abdominal CT may show malrotation but is less specific for it. Barium enema and radionuclide scans have no role in the diagnosis of malrotation

• Question 455:

  You see a 2-month-old infant in the emergency department for vomiting. The mother says that the baby has been spitting up more over the past few days and has become more irritable. She denies any fever, diarrhea, or change in formula. The mother tells you that there is a family history of "heartburn" and that her other children have all spit up. The infant has some emesis in the emergency department that seems to be formula mixed with some bile. The infant is intermittently irritable and sleepy.

  What is the most concerning diagnosis that this could be?

  A. biliary atresia

  B. malrotation

  C. pyloric stenosis

  D. imperforate anus

  E. diaphragmatic hernia

  Correct Answer: B Section: (none)

  Explanation:

  Bilious emesis in an infant is malrotation until proven otherwise. Malrotation can lead to a midgut volvulus. The volvulus can result in bowel ischemia and necrosis. This makes bilious emesis in a newborn a concerning finding. Pyloric stenosis would cause nonbilious emesis. Imperforate anus would present with the failure of stool passage. Diaphragmatic hernia will present with poor feeding, drooling, and respiratory embarrassment The best radiographic test in the diagnosis of malrotation is an UGI contrast study with small bowel follow through. This will identify the duodenum and its location relative to the ligament of Treitz. The characteristic finding in a midgut volvulus is the "corkscrew" sign, which is seen as contrast media traverses the kinked intestine. An abdominal CT may show malrotation but is less specific for it. Barium enema and radionuclide scans have no role in the diagnosis of malrotation.

• Question 456:

  While in the emergency department you see a 3-week-old infant. The mother says that the child felt warm earlier in the day and has not been eating very well. The infant has a temperature of 100.9°F and has mildly decreased tone. What is the most appropriate initial management?

  A. Give acetaminophen and reassess in a few hours.

  B. Draw a blood culture, recommend increased fluid intake, and follow-up for re-examination in 24 hours in the primary pediatrician's office.

  C. Admit to the hospital and perform a full "sepsis workup."

  D. Draw a blood culture, give a shot of ceftriaxone (Rocephin) to cover for any infections and follow-up in 2448 hours.

  E. Get a urine culture and begin trimethoprim/sulfamethoxazole (Septra).

  Correct Answer: C Section: (none)

  Explanation:

  A fever in the first 46 weeks of life needs to be treated very aggressively. There are no reliable clinical or laboratory findings currently available that can discriminate between a nominal viral illness and a serious bacterial infection. In the newborn period, fever may be the only indicator of bacteremia or meningitis. Any rectal temperature greater than 100.5°F should trig ger a full sepsis workup. This should include cultures of the blood, urine, and spinal fluid. In this age range, empiric antimicrobials should be initiated that should cover for GBS, E. coli, and Listeria monocytogenes. A commonly used regimen is ampicillin and gentamicin. Many would also include empiric acyclovir in this age range. In infants, the routine use of antipyretics should be discouraged. A blood culture alone is not an adequate screening tool for meningitis. While a urinary tract infection (UTI) is a common cause of infection in infants, a more complete evaluation would be warranted.

• Question 457:

  A 5-year-old male is admitted to the hospital following a 3-week history of spiking fevers and fatigue. Your examination reveals pale mucous membranes and skin. You also find splenomegaly.

  The best course of care for this young man would be which of the following?

  A. initiate high-dose aspirin therapy (100 mg/kg/day)

  B. initiate "renal sparing" course of oral prednisone

  C. a repeat bone marrow evaluation with AFB (acid fast bacilli) staining and mycobacterial cultures

  D. obtain serum for Lyme enzyme immunoassay(EIA) testing and begin an empiric course of doxycycline

  E. obtain EBV serologies (IgM and IgG) and treat symptomatically with comfort measures

  Correct Answer: E Section: (none)

  Explanation:

  The most common malignancy in childhood is leukemia/lymphoma. The most common solid tumors of childhood are CNS tumors, followed by neuroblastoma and Wilms tumors. The mildly elevated WBC with lymphocyte predominance with the presence of "atypical" lymphocytes would indicate that his child most likely has acute EBV infection (infectious mononucleosis). This acute EBV infection is usually subclinical in younger children, but can be manifested by acute hemolytic anemia and splenomegaly. Testing for the diagnosis of EBV includes EBV DNA PCR and heterophile antibody response testing (monospot test). Diagnosis usually is made based upon serology testing for anti-EBV IgG and IgM levels. There is no specific therapy indicated for the acute EBV infections. Acute Lyme disease is very uncommon in children. The early stage of acute Lyme disease is characterized by a distinctive rash (erythema migrans). This is then followed by a multiple annular rash of disseminated Lyme disease. Often seen in this stage is cranial nerve palsies, specifically facial nerve (CN VII) palsy. Late Lyme disease is characterized by recurrent arthritis and arthralgia. Serologic testing is only recommended if there is a very high clinical index of suspicion, unlike this child. Acute systemic-onset JRA (Still disease) can present in a child of this age in a nonspecific manner (i.e., fever of unknown origin). Children with Still disease will typically have dramatic elevations in acute-phase reactants (i.e., ESR). This child's ESR being 5 would go against JRA.

• Question 458:

  A 5-year-old male is admitted to the hospital following a 3-week history of spiking fevers and fatigue. Your examination reveals pale mucous membranes and skin. You also find splenomegaly.

  This child has an extensive evaluation by the Hematology-Oncology consultants. Their evaluation excludes the presence of a malignancy. The extensive evaluation did reveal that the child has a WBC count of 22,000 with 41% monocytes and 12% "atypical" lymphocytes. His hematocrit is 28% and erythrocyte sedimentation rate (ESR) is 5.

  This child likely has which of the following diseases?

  A. Lyme disease

  B. acute Epstein-Barr virus (EBV) infection

  C. systemic lupus erythematosus (SLE)

  D. juvenile rheumatoid arthritis (JRA) E. acute hematogenous tuberculosis (TB)

  Correct Answer: B Section: (none)

  Explanation:

  The most common malignancy in childhood is leukemia/lymphoma. The most common solid tumors of childhood are CNS tumors, followed by neuroblastoma and Wilms tumors. The mildly elevated WBC with lymphocyte predominance with the presence of "atypical" lymphocytes would indicate that his child most likely has acute EBV infection (infectious mononucleosis). This acute EBV infection is usually subclinical in younger children, but can be manifested by acute hemolytic anemia and splenomegaly. Testing for the diagnosis of EBV includes EBV DNA PCR and heterophile antibody response testing (monospot test). Diagnosis usually is made based upon serology testing for anti-EBV IgG and IgM levels. There is no specific therapy indicated for the acute EBV infections. Acute Lyme disease is very uncommon in children. The early stage of acute Lyme disease is characterized by a distinctive rash (erythema migrans). This is then followed by a multiple annular rash of disseminated Lyme disease. Often seen in this stage is cranial nerve palsies, specifically facial nerve (CN VII) palsy. Late Lyme disease is characterized by recurrent arthritis and arthralgia. Serologic testing is only recommended if there is a very high clinical index of suspicion, unlike this child. Acute systemic-onset JRA (Still disease) can present in a child of this age in a nonspecific manner (i.e., fever of unknown origin). Children with Still disease will typically have dramatic elevations in acute-phase reactants (i.e., ESR). This child's ESR being 5 would go against JRA.

• Question 459:

  A 5-year-old male is admitted to the hospital following a 3-week history of spiking fevers and fatigue. Your examination reveals pale mucous membranes and skin. You also find splenomegaly.

  You are concerned about a possible malignancy. What is the most common malignancy of childhood?

  A. medulloblastoma

  B. Wilms' tumor

  C. leukemia

  D. neuroblastoma

  E. rhabdomyosarcoma

  Correct Answer: C Section: (none)

  Explanation:

  The most common malignancy in childhood is leukemia/lymphoma. The most common solid tumors of childhood are CNS tumors, followed by neuroblastoma and Wilms tumors. The mildly elevated WBC with lymphocyte predominance with the presence of "atypical" lymphocytes would indicate that his child most likely has acute EBV infection (infectious mononucleosis). This acute EBV infection is usually subclinical in younger children, but can be manifested by acute hemolytic anemia and splenomegaly. Testing for the diagnosis of EBV includes EBV DNA PCR and heterophile antibody response testing (monospot test). Diagnosis usually is made based upon serology testing for anti-EBV IgG and IgM levels. There is no specific therapy indicated for the acute EBV infections. Acute Lyme disease is very uncommon in children. The early stage of acute Lyme disease is characterized by a distinctive rash (erythema migrans). This is then followed by a multiple annular rash of disseminated Lyme disease. Often seen in this stage is cranial nerve palsies, specifically facial nerve (CN VII) palsy. Late Lyme disease is characterized by recurrent arthritis and arthralgia. Serologic testing is only recommended if there is a very high clinical index of suspicion, unlike this child. Acute systemic-onset JRA (Still disease) can present in a child of this age in a nonspecific manner (i.e., fever of unknown origin). Children with Still disease will typically have dramatic elevations in acute-phase reactants (i.e., ESR). This child's ESR being 5 would go against JRA.

• Question 460:

  Afather and son come to your office because of persistent diarrhea. They relate the presence of watery diarrhea for over 2 weeks. They noted that the diarrhea began after returning from a Boy Scout camping trip in the Rocky Mountains. The diarrhea has waxed and waned for 2 weeks. It is nonbloody and foul smelling. They have had increased flatulence and mild abdominal cramping.

  What would be the most appropriate treatment?

  A. oral ciprofloxacin

  B. oral metronidazole

  C. bismuth subsalicylate (Pepto-Bismol)

  D. an antidiarrheal agent only; no antimicrobials necessary

  E. oral rehydration only

  Correct Answer: B Section: (none)

  Explanation:

  G. lamblia is a common protozoan which can be acquired by ingesting unfiltered water. It is seen frequently in people who drink fresh stream water. It is a cause of chronic, nonbloody diarrhea. There is typically a large amount of gas and cramping associated with Giardia infections. RMSF does not typically cause a gastroenteritis. Children with RMSF will commonly have fevers, headaches, and a petechial rash. Rotavirus and Norwalk viruses typically cause acute, self-limited gastroenteritis. The diarrhea is nonbloody, nonmucousy, and typically lasts a few days. The most appropriate treatment for giardiasis is oral metronidazole. Oral rehydration is an important mainstay in the treatment of diarrhea of any cause but is not a specific treatment for giardiasis. Ciprofloxacin is commonly used for traveler's diarrhea caused by E. coli.