USMLE USMLE Certifications USMLE-STEP-2 Questions & Answers

• Question 41:

  A10-year-old boy presents with a 1-day history of fever, cough, and chest pain. He has not been eating and has been listless. He does not have any previous history of health problems. On physical examination, his temperature is 40°C, and he is tachypneic. He looks ill. He has rales on his left posterior lower lung fields. You order a chest x-ray. Which of the following organisms is most likely responsible for his pneumonia?

  

  

  A. Haemophilus influenzae

  B. Mycoplasma pneumoniae

  C. Pneumocystis carinii

  D. Staphylococcus aureus

  E. Streptococcus pneumoniae

  Correct Answer: E

  This is a "round pneumonia," most commonly caused by S. pneumoniae. Onset of this disease is relatively acute. H. influenzae type B is an uncommon cause of systemic infections because of routine immunization. Mycoplasma is the most common cause of communityacquired pneumonia in this age group. Patients typically have a more gradual onset of symptoms. Pneumocystis does not cause pneumonia in otherwise healthy children. S. aureus can cause pneumonia in healthy children, but it is not as common as S. pneumoniae or Mycoplasma.

• Question 42:

  Your next patient is a 4-month-old infant who is returning to have her ear checked. You diagnosed her with otitis media 2 weeks ago, and she has taken 10 days of amoxicillin. She is feeling well, and her mother's only concern is that she has developed a diaper rash over the last 3 days. The mother has been using emollient creams on it which have not helped. On physical examination, there are no abnormal findings except for the rash. Which of the following is the most likely diagnosis?

  A. allergic dermatitis

  B. bullous impetigo

  C. Candida dermatitis

  D. irritant dermatitis

  E. seborrheic dermatitis

  Correct Answer: C

  Diaper dermatitis is a very common problem in infants. The infant's rash is due to Candida. Candida dermatitis is red, without bullae, and has satellite lesions at the margins. It is common in infants, especially when they have been on antibiotics. In bullous impetigo, the skin is initially erythematous and then bullae develop. Allergic dermatitis and irritant dermatitis are the most prominent on the convex areas and are intensely red. In seborrheic dermatitis, children tend to have the rash on the scalp, neck, and face also. It is scaly and more prominent in the intertriginous areas.

• Question 43:

  An 8-year-old girl presents for a checkup. She is new to your practice. The mother states that she has always been small for her age; otherwise, she has been well. She is short and has a height age of 4 years, 4 months. You note some abnormalities in her general appearance as shown in the figure.

  

  As you continue your physical examination, you remember that congenital heart disease is common in this particular syndrome. Which of the following is the most likely congenital heart defect in patients with this syndrome?

  A. supravalvular aortic stenosis

  B. atrioventricular (AV) canal defects

  C. coarctation of the aorta

  D. pulmonary valvular stenosis

  E. mitral valve prolapse

  Correct Answer: C

  Turner syndrome is associated with coarctation of the aorta and aortic stenosis.Williams syndrome is associated specifically with supravalvular aortic stenosis. In Noonan syndrome, the cardiac defect most often is pulmonary valvular stenosis or an atrial septal defect. Marfan syndrome is associated with mitral valve prolapse and aortic root dilatation. Septal defects, primarily endocardial cushion defects, are the most common heart defects among children with Down syndrome.

• Question 44:

  A 3-month-old infant is brought to your office in the winter with a history of 1 day of vomiting, followed by 3 days of diarrhea. She has had six to eight stools per day, which are loose and foul smelling. On examination, she looks well. Which of the following viruses is the most likely cause of her illness?

  A. adenovirus

  B. enterovirus

  C. human herpesvirus, type 6

  D. respiratory syncytial virus

  E. rotavirus

  Correct Answer: E

  Because many childhood viral illnesses have seasonal presentations, the etiologic agent may be suspected on the basis of clinical and seasonal presentation. Yearly winter outbreaks of bronchiolitis and pneumonia are associated with respiratory syncytial virus. Summer outbreaks of gastroenteritis are associated with enterovirus, while winter outbreaks are associated with rotavirus. Although adenovirus can cause diarrhea, it more commonly causes respiratory symptoms. Human herpes virus type 6 is the etiologic agent in roseola infantum.

• Question 45:

  An 11-month-old girl presents to your office with a fever of 39°C she has had for 2 days. She has also vomited frequently and had decreased fluid intake. She looked tired and ill but on examination, had no apparent source of infection. She appeared to be 510% dehydrated. Her urinalysis shows a urine specific gravity of 1.030, trace blood, and protein. Nitrite and leukocyte esterase are both positive. Microscopic examination of unspun urine shows >100 white blood cells (WBCs) and 05 red blood cells (RBCs) per high-power field, as well as many bacteria. Aurine culture is sent. Which of the following is the most appropriate management plan?

  A. Treat only if the culture is positive.

  B. Admit for intravenous (IV) hydration and IV antibiotics.

  C. Treat with intramuscular ceftriaxone and have her follow-up in the office the following day.

  D. Treat with trimethoprimsulfamethoxazole, and have her followup in the office the following day.

  E. Prescribe amoxicillin and start oral hydration.

  Correct Answer: B

  Urine for urinalysis and culture must be properly obtained. Catheterization is the most reliable method of the choices offered. Suprapubic tap is considered the "gold-standard" but is not always technically feasible, especially in an outpatient office setting. Amidstream, clean catch specimen would be acceptable in an older, toilet-trained child. "Bagged" specimens are not recommended because of possible skin or fecal contamination of the specimen. Similarly, obtaining a sample from a diaper or potty would be unacceptable. Urinalysis includes dipstick method and microscopic examination. Leukocyte esterase (an enzyme in WBC) and nitrites suggest probable infection. Microscopic analysis of unspun urine for WBC (>10/ highpower field) or bacteria is also predictive of infection. RBCs are often present in a UTI. The patient is vomiting and dehydrated; this may indicate possible pyelonephritis. The most appropriate course would be IV hydration and empiric treatment with antibiotics (ceftriaxone) while awaiting cultures. Children with pyelonephritis are at increased risk of renal scarring, especially younger children, and should be treated early. E. coli is the most common organism cultured; others include Proteus, Klebsiella, S saprophyticus, and Enterococcus. The occurrence of a UTI in a girl under age 35 years and in a boy of any age may be a marker for an underlying congenital anatomic abnormality, in particular, vesicourethral reflux. Radiologic investigation with renal ultrasound and VCUG is recommended

• Question 46:

  A woman at 31 weeks' gestation complains of feeling dizzy and lightheaded when she lies on her back. She is Rh negative but denies vaginal bleeding, abdominal trauma, or abdominal pain. The diagnosis is

  probably the supine hypotensive syndrome.

  During this woman's labor, the nurse describes the presenting part as engaged when the woman is 6 cm

  dilated. Which of the following is the most accurate definition of engagement in a woman with a vertex

  presentation?

  A. The vertex has passed through the pelvic inlet.

  B. The vertex reaches the pelvic floor.

  C. The biparietal diameter has passed through the pelvic inlet.

  D. The biparietal diameter has reached the pelvic floor.

  E. The vertex is at plus 1 station.

  Correct Answer: C

  The strict definition of the cardinal movement of labor, called engagement, is given as choice C. Among other things, this means that the presenting part is fixed in the true pelvis and a prolapsed umbilical cord is unlikely to occur. Often, the fetal head is considered to be engaged when the vertex is at 0 station, the level of the ischial spines. Although engagement is conclusive evidence of an adequate pelvic inlet, its absence is not always indicative of pelvic contraction. Nevertheless, the incidence of pelvic contraction is higher in primigravid women whose presenting part is not engaged.

• Question 47:

  Which feature of fibrocystic disease of the breast is associated with the greatest risk of developing breast cancer?

  A. number of nodules

  B. serous nipple discharge

  C. size of the dominant mass

  D. presence of epithelial hyperplasia

  E. presence of a palpable axillary node

  Correct Answer: D

  Fibrocystic disease includes a variety of histologic findings. Typical is proliferation and hyperplasia of the lobular, ductal, and acinar epithelium. Histologic variants include variable- sized cysts, adenosis, fibrosis, duct ectasia, apocrine metaplasia, and others. Ductal epithelial hyperplasia and apocrine metaplasia with atypia are the findings associated with the greatest risk of subsequent breast cancer. The presence of histologic atypia increases the woman's chance of breast cancer fivefold.

• Question 48:

  A pediatrician asks you to see a 13-year-old girl who has not begun to menstruate and has a 6-month history of pelvic and lower abdominal pain at approximately 1-month interval. She has Tanner stage 3 pubic hair and breast development. Her growth spurt occurred about 1 year ago and her current height is 65 in. (165 cm). She has never had sexual intercourse. On examination of her external genitalia the presence of Tanner stage 3 pubic hair is confirmed. The labia are normal. There is no obvious vaginal opening and there is bulging between the labia minora.

  Which one of the following laboratory tests is found in women with the androgen insensitivity syndrome?

  A. normal adult female testosterone concentrations

  B. normal adult male testosterone concentrations

  C. low LH concentrations

  D. elevated prolactin concentrations

  E. low TSH (thyroid-stimulating hormone) concentrations

  Correct Answer: B

  The androgen insensitivity syndrome is the result of abnormal testosterone receptors in genetic males with functioning testes. The testes secrete normal amounts of testosterone after puberty and adult male concentrations are found. Serum LH concentrations are normal or even elevated, presumably because of the testosterone receptor defect in the hypothalamus and pituitary gland. As a result, secretion of LH is often increased. Serum prolactin and TSH concentrations are normal because absent testosterone receptors have no effect on pituitary secretion of these hormones.

• Question 49:

  A 24-year-old woman has a MSAFP of 0.5 MOM (multiples of the median) at 17 weeks' gestation. Which of the following fetal abnormalities is most likely to occur with this MSAFP?

  A. spina bifida

  B. omphalocele

  C. gastroschisis

  D. bladder exstrophy

  E. trisomy 21

  Correct Answer: E

  Production of AFP begins in the yolk sac and then moves to the fetal liver and, to a lesser extent, the fetal gastrointestinal tract. Choices A. through D. result in an increased maternal serum AFP (MOM greater than 2.0) because all are open defects of the fetus that result in an increase in amniotic fluid concentrations and then maternal serum concentrations of AFP. Trisomy 21 (Down syndrome) is associated with a decreased MSAFP. In clinical practice, measurement of MSAFP is combined with serum chorionic gonadotropin (hCG) and unconjugated estriol (E3). These three tests are commonly called a triple screen or triple marker screen and together improve the sensitivity over each test alone. Approximately 60% of trisomy 21 fetuses in women under age 35 years, and more than 75% in women over 35 will be detected using a multiple marker screening test. Screening for these defects is most sensitive between 16 and 18 gestational weeks, but the test should be offered to all pregnant women between 15 and 22 gestational weeks.

• Question 50:

  With reference to the above patient, you tell her that her expected delivery date (EDD) is which of the following?

  A. May 18

  B. August 18

  C. May 11

  D. August 11

  E. May 25

  F. June 1

  Correct Answer: E

  Calculation of the EDD is by using Naegele's rule. Seven days are added to the first day of the LMP, then 3 months are subtracted. Application of Naegele's rule is accurate only for women who have regular menstrual cycle intervals of 2830 days.