USMLE USMLE-STEP-2 Online Practice Questions and Exam Preparation

USMLE USMLE-STEP-2 Online Questions & Answers

• Question 181:

  A 49-year-old woman with a history of migraine headaches reports 6 days of persistent headache, nausea, and recurrent vomiting. On examination, the patient is orthostatic. Electrolytes show a bicarbonate of 42 and a blood gas is obtained revealing a pH of 7.53, carbon dioxide of 53, and PO2 of 85. What is the underlying acid-base abnormality?

  A. metabolic acidosis
  B. metabolic alkalosis
  C. respiratory acidosis
  D. respiratory alkalosis
  E. respiratory alkalosis and metabolic acidosis
  B. metabolic alkalosis

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  Explanation

  The pH of 7.53 indicates alkalosis as the primary disorder (normal pH is 7.40). A high bicarbonate is consistent with a metabolic cause of the alkalosis. The high carbon dioxide of 53 (normal is 40) is compensating for the primary disorder (alkalosis) in an attempt to bring the pH closer to normal. Metabolic alkalosis results from renal bicarbonate reabsorption. Processes which maintain persistent high reclamation of bicarbonate include dehydration, hypokalemia, hypercapnea, and mineralocorticoid excess.

• Question 182:

  A study finds that the incidence of asthma in your community is higher than expected, and that 40% of the homes in your community are heated with forced air. Which of the following best describes this study design?

  A. ecological study
  B. cross-sectional study
  C. cohort study
  D. case-control study
  E. prospective study
  A. ecological study

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  Explanation

  Ecological studies compare groups not individuals. The unit of observation in the above study was a community not individuals. A cross-sectional study design would have looked at the incidence of asthma in those who also owned the particular home heating system at a particular point in time. A cohort study would have taken disease-free individuals in the community who also owned the home heating system and followed them over time to see who developed disease. A case-control approach would have taken individuals with and without asthma and identified how many from each group also had the particular home heating system

• Question 183:

  A 6-year-old Caucasian female has breast enlargement (Tanner stage II) and coarse curly pubic hair. She is not yet menstruating. She is otherwise healthy and has normal growth parameters. There are no signs of virilization and her abdominal examination reveals no masses. Examination of the vaginal area shows signs of estrogenization.

  Which of the following is the most likely preliminary working diagnosis?

  A. precocious puberty
  B. premature thelarche
  C. premature pubarche
  D. normal development
  E. precocious menarche
  A. precocious puberty

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  Explanation

  Precocious puberty has been redefined for girls as the presence of either pubic hair or breast development before age 6 for African Americans and age 7 for Caucasians. Premature thelarche is the isolated development of breasts, with no other secondary sexual development. Premature pubarche is the isolated development of pubic or axillary hair (sexual hair). Precocious menarche is a rare form of incomplete precocious puberty with cyclic menstruation but no other secondary sexual characteristics.

• Question 184:

  A 60-year-old man disappears from his home and travels 100 miles to a small town, where he opens a small grocery store using a different name. Six weeks later, he awakens in some agitation, uses his original name, and asks to know where he is. He wishes to return to his home. Which of the following is the most likely diagnosis?

  A. dissociative amnesia
  B. dissociative fugue
  C. dissociative identity disorder
  D. depersonalization disorder
  E. dissociative disorder not otherwise specified
  B. dissociative fugue

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  Explanation

  Dissociative fugue is classically typified by a person's suddenly and unexpectedly traveling away from his or her home, assuming a new identity, and eventually recovering from the fugue or flight, unable to recall the events that took place during the episode. Dissociative amnesia is a more generalized term given to an inability to recall significant personal information. Dissociative identity disorder is the current diagnostic term for what was classically called multiple personality disorder. Depersonalization disorder is an alteration of experience in which an individual feels like an outside observer of his or her body or mental processes. Dissociative disorder not otherwise specified is a name given to other dissociative illnesses not specifically listed in DSM-IV-TR, such as dissociative states occurring in individuals subjected to brainwashing or indoctrination while held captive by terrorists.

• Question 185:

  An athletic 12-year-old boy complains of left knee pain when he runs and plays sports. The pain resolves when he rests. He has otherwise been well. His physical examination is normal, except for swelling and increased prominence over the left tibial tubercle. Aradiograph of the left knee is normal.

  Which of the following is the most likely diagnosis?

  A. Legg-Calv?Perthes disease
  B. Osgood-Schlatter disease
  C. patellar subluxation
  D. popliteal cyst
  E. slipped capital femoral epiphysis
  B. Osgood-Schlatter disease

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  Explanation

  Osgood-Schlatter results from microfractures and inflammation of the tibial tubercle where the patellar tendon inserts. It is most commonly seen in young adolescents who are involved in athletics. Legg- Calv? Perthes disease is idiopathic avascular necrosis of the capital femoral epiphysis and presents between the ages of 2 and 12 with a painless limp. Patellar subluxation is usually due to a congenital deficiency within the patellofemoral joint. On examination, these patients have tenderness over the inferior surface of the patella and terminal subluxation of the patella when the knee is fully extended. Popliteal cysts are usually asymptomatic and present with a fluidfilled mass in the popliteal fossa. The symptoms of slipped capital femoral epiphysis are variable but typically involve hip pain and limp. On examination, patients have limitation of motion in the hip. It is most common in obese adolescents

• Question 186:

  A 28-year-old man with a past history of bilateral orchiopexy for cryptorchidism presents with a painless, unilateral right scrotal enlargement. On examination, there is a palpable right testicular mass and enlarged inguinal nodes. Scrotal ultrasonography demonstrates heterogeneity of the testis, with an associated hydrocele. A CT scan of the abdomen and pelvis demonstrated right-sided retroperitoneal adenopathy. CT scan of the chest is normal.

  Which of the following would help confirm the diagnosis?

  A. transscrotal needle biopsy
  B. transscrotal aspiration of the hydrocele for cytology
  C. radical orchiectomy through an inguinal incision
  D. transscrotal exploration and orchiectomy
  E. laparotomy with pelvic and retroperitoneal node dissection
  C. radical orchiectomy through an inguinal incision

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  Explanation

  Cryptorchidism increases the risk of developing a testicular malignancy. This patient has a solid testicular mass which should be presumed to be secondary to a testicular malignancy. Optimal surgical management is inguinal exploration, control of the spermatic cord, biopsy of the mass, and radical orchiectomy with high ligation of the cord, if tumor is confirmed. Transscrotal aspiration, exploration, or needle biopsy is contraindicated because of risk of tumor spillage, and risk of altering the lymphatic drainage of the scrotum. Laparotomy and retroperitoneal node dissection is not indicated until after confirmation of the diagnosis and excision of the primary tumor. This patient has seminoma with disease spread to ipsilateral regional lymph nodes.

• Question 187:

  Select the ONE best lettered option that is most closely associated with the question below. A40-year- old male with purulent, bloody sinus drainage, hemoptysis, and rising creatinine

  A. rheumatoid arthritis
  B. SLE
  C. Wegener's granulomatosus
  D. polyarteritis nodosa
  E. Goodpasture syndrome
  F. fibromyalgia
  G. osteoarthritis (OA)
  H. giant cell arteritis
  I. sarcoidosis
  C. Wegener's granulomatosus

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  Explanation

  Wegener granulomatosis affects males and females equally, can occur at any age, and is extremely rare in African Americans. Patients typically present with severe upper respiratory tract symptoms. Nasal perforation and saddle nose deformity may occur. Pulmonary involvement (cough, hemoptysis, or dyspnea are common presenting symptoms/signs) is present in 8590% of patients, renal disease in 7080% of patients, eye involvement in 5055%, and skin lesions in 4050%. Antineutrophil cytoplasmic antibodies (C- ANCA) is positive in 90% of patients. ESR typically is high.

• Question 188:

  A10-year-old boy presents with a 3- to 4-day history of left ear pain. He is afebrile; he has had no symptoms of cold or cough. He has been swimming daily. On physical examination, there is pain on moving the pinna and the tragus. There is erythema and swelling of the ear canal; the tympanic membrane is obscured by thick white discharge.

  Which of the following is the most likely diagnosis?

  A. otitis externa
  B. furunculosis
  C. otitis media with effusion
  D. mastoiditis
  E. foreign body in the ear
  A. otitis externa

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  Explanation

  Otitis externa is an infection of the external ear canal. Predisposing factors include excessive wetness (swimming), dryness (lack of protective cerumen), trauma (foreign body), and other skin pathology (eczema). It is characterized by pain, accentuated by moving the pinna and especially the tragus; edema and inflammation of the canal; and discharge. Furuncles usually cause a localized swelling or papule in the hairbearing part of the canal. If the tympanic membrane is not visualized, otitis media is hard to differentiate from otitis externa. Otitis media does not cause pain with movement of the pinna. In severe otitis externa, the periauricular edema may push the pinna forward; this may be confused with mastoiditis. In mastoiditis, however, the postauricular fold is usually obliterated. There is often a history of otitis media and hearing loss and tenderness over the mastoid antrum.

• Question 189:

  A 35-year-old man with no previous psychiatric history is referred by his family physician for psychiatric evaluation. The family physician has been following the man for mild hyperlipidemia, which is currently being successfully treated with dietary changes alone. The man reports that he has been happily married for 10 years and has two children. He has been working as an accountant and has generally enjoyed his job. About 2 months ago, with no obvious precipitating event, he says, the man began to feel very blue, with a drop in his desire to play with his children and to compete in his usual volleyball league games. He reports that he has lost most of his libido and is having difficulty sleeping, with earlymorning wakening. He reports that his appetite has become very poor over the past 2 months, and he estimates that he has lost 10 lbs over that time.

  Which of the following is the most likely diagnosis?

  A. Alzheimer's disease
  B. schizophrenia
  C. major depressive disorder
  D. metastatic cancer to the brain
  E. systemic lupus erythematosus
  C. major depressive disorder

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  Explanation

  The essential feature of a major depressive disorder is the development of a major depressive episode without a history of mania or hypomania. The hallmarks of a major depressive episode are a subjective sense of dysphoria and a loss of interest in previously enjoyed activities, also called anhedonia. Depressed patients often report decreased libido, sleep disturbance, and appetite disturbance. It would be important to rule out organic causes for this man's disorder, such as hypothyroidism or the relatively rare phenomenon of metastatic cancer to the brain in a 35-year-old. Given the patient's age and recent onset of symptoms, Alzheimer's disease is unlikely. Schizophrenia generally has a gradual onset and is accompanied by psychotic symptoms such as hallucinations and delusions

• Question 190:

  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 is the most likely diagnosis?

  A. androgen insensitivity syndrome
  B. mittelschmerz (ovulation pain)
  C. Müllerian and vaginal agenesis
  D. gonadal dysgenesis
  E. imperforate hymen
  E. imperforate hymen

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  Explanation

  The presence of pubertal events except external menstruation and the bulging of the hymen causing retrograde menstruation as a cause of her cyclic pain establish the diagnosis of imperforate hymen. Strictly, these women have cryptomenorrhea, not amenorrhea. Women with mittelschmerz (ovulation pain) menstruate cyclically. While pubertal events except menstruation occur normally in women with Müllerian/ vaginal agenesis, cyclic pain is absent because the uterus is hypoplastic or absent and there is no endometrium to shed. Women with gonadal dysgenesis do not develop breasts or pubic hair and have primary amenorrhea. The most common form of gonadal dysgenesis is 45,X Turner syndrome and affected females are less than 62 in. tall.