USMLE USMLE Certifications USMLE-STEP-2 Questions & Answers

• Question 491:

  A 6-month-old infant is diagnosed with her first episode of otitis media. She does not have any allergies to medications. Which of the following medications would be the recommended initial therapy for this infant?

  A. amoxicillin

  B. amoxicillin-clavulanic acid

  C. cephalexin

  D. ceftriaxone

  E. erythromycin

  Correct Answer: A

  H. influenzae, S. pneumoniae, and Moraxella catarrhalis are the most common bacterial pathogens in otitis media of children. Amoxicillin is still the initial drug to use in uncomplicated otitis media because of its good coverage, except for beta-lactamase-positive organisms, and its excellent safety profile. The other drugs (except for erythromycin) are acceptable second-line medications

• Question 492:

  Among the conditions that cause edema of the eyelids is orbital cellulitis. This is a serious infection that must be recognized early and treated aggressively if complications are to be avoided. Which of the following features is useful in differentiating orbital cellulitis from periorbital (preseptal) cellulitis?

  A. proptosis

  B. elevated WBC count

  C. fever

  D. lid swelling

  E. conjunctival inflammation

  Correct Answer: A

  Proptosis and limitation of extraocular motility distinguish orbital cellulitis from periorbital cellulitis. Fever, lid swelling, redness of the eye, and leukocytosis generally are present in either condition. Orbital cellulitis (infection within the orbit) may follow directly from a wound near the orbit or may result from bacteremia, but the most common source involves extension from the paranasal sinuses. The organisms most frequently implicated as pathogens are H. influenzae, S. aureus, group A beta- hemolytic Streptococci, and S. pneumoniae. The risk of complication is great, with extension resulting in cavernous sinus thrombosis, meningitis, or brain abscess. Prompt hospitalization and parenteral antibiotic therapy are indicated

• Question 493:

  Otitis media occurring during the first 8 weeks of life deserves special consideration, because the bacteria responsible for infections during this time may be different from those that affect older infants and children. Which of the following organisms is the most likely to cause otitis media in these infants?

  A. Chlamydia trachomatis

  B. E. coli

  C. Neisseria gonorrhoeae

  D. Treponema pallidum

  E. Toxoplasma gondii

  Correct Answer: B

  C. trachomatis is considered an unusual cause of otitis media at any age. N. gonorrhoeae causes conjunctivitis in the newborn. Syphilis and toxoplasmosis cause congenital infections. E. coli is one of the neonatal pathogens that also cause otitis media in neonates. The symptoms of otitis media in newborns are often similar to those of sepsis; they are subtle and nonspecific and may include poor feeding, lethargy, vomiting, or diarrhea. Once the diagnosis is established, the initial therapy should be similar to that for neonatal sepsis, such as parenteral ampicillin and cefotaxime. Under ideal circumstances, the results of cultures obtained by tympanocentesis may then allow further treatment with a more specific antibiotic of low toxicity. Older infants may respond well to oral therapy but require frequent observation.

• Question 494:

  A14-year-old boy presents with sudden onset of pain and swelling of his right testicle. There was no history of trauma, he is not sexually active, and denies any history of penile discharge. On examination, the scrotum is swollen and tender. The cremasteric reflex is absent. A testicular flow scan shows a "cold spot" or absent flow to the affected side. Which of the following is the most likely cause?

  A. inguinal hernia

  B. hydrocele

  C. epididymitis

  D. testicular torsion

  E. torsion of the appendix testis

  Correct Answer: D

  Testicular torsion is the most common cause of testicular pain in boys 12 years and older and is uncommon in those under 10 years. It may be sometimes related to trauma or injury but may occur spontaneously. If not diagnosed early, loss of blood flow to the testicle may result in permanent loss of testicular function. Torsion of the testicular appendix usually occurs between the ages of 2 and 11 years. The testicular appendix is a vestigial stalk at the upper pole of the testis. Torsion results in pain and swelling of the scrotum, but the onset of pain is more gradual. There is a 3- to 5-mm indurated, tender mass at the upper pole of the testis. It may sometimes be visible as a "blue-dot." Testicular scan may be helpful when this cannot be clinically differentiated from testicular torsion. A hydrocele is a painless collection of fluid in the tunica vaginalis. Transillumination confirms that the mass is filled with fluid. Hydroceles are present in 12% of male newborns and usually resolve by age 1 year. In older boys, a communicating hydrocele may be associated with an inguinal hernia. Inguinal hernias usually appear as a bulge in the inguinal area extending into the scrotum. Hernias are painless, and are more noticeable during crying or straining. They are painful only when strangulated or incarcerated. Epididymitis is an acute inflammation of the epididymis, and is more common in sexually active adolescents. Urinalysis shows pyuria and the etiology may be gonococcus or chlamydia but is often undetermined.

• Question 495:

  A 1-year-old African American infant is in for well-child care. He is primarily breast-fed. His parents do not give him much solid food because he has no teeth. He receives no medications or supplements. His parents are concerned about his bowed legs. On examination, you note some other bony abnormalities including frontal bossing, enlargement of the costochondral junctions, a protuberant sternum (pigeon chest), and severe bowing of the legs. You obtain x-rays to confirm your clinical diagnosis and also note a healing fracture of the left femur. Which of the following is the most likely diagnosis?

  A. osteogenesis imperfecta

  B. scurvy

  C. congenital syphilis

  D. rickets

  E. chondrodystrophy

  Correct Answer: D

  Babies who are exclusively breast-fed for prolonged periods of time are at risk for developing rickets. Dark-skinned infants are at high risk, especially during winter months when they receive inadequate sunlight. Supplementation with vitamin D is recommended in children who are at high risk, as well as pregnant and lactating mothers. Clinical features include craniotabes, a thinning of the outer table of the skull. This may also occur in osteogenesis imperfecta. Enlargement of the costochondral junctions rachitic rosary) may be seen in rickets, scurvy, and chondrodystrophy. Other features may include delayed primary teeth, enamel defects, and caries. There may be thickening of the wrists and ankles; bending of the femur, tibia, and fibula result in bowlegs or knock-knees. Greenstick fractures of long bones may occur without symptoms. Diagnosis is based on history of inadequate vitamin D intake and clinical features. Diagnosis may be confirmed by x-rays and chemistry; serum calcium is low or normal, serum phosphorus is low, serum alkaline phosphatase is elevated, and serum 25- hydroxycholecalciferol is decreased. Breast milk contains adequate vitamin C as long as the mother is not deficient.

• Question 496:

  A 5-year-old febrile child presents with swelling of the right eyelid. Proptosis and limitation of ocular movements is noted. Which of the following is the most likely diagnosis?

  A. retinoblastoma

  B. orbital cellulitis

  C. periorbital cellulitis

  D. neuroblastoma

  E. hyphema

  Correct Answer: B

  Orbital (also referred to as postseptal) cellulites is a medical emergency. It is a bacterial infection of the orbit. It must be distinguished from periorbital (also referred to as preseptal) cellulitis by the presence of proptosis or limitations of extraocular movements. When orbital cellulitis is suspected, cultures of blood and CSF should be obtained, appropriate antibiotics should be administered intravenously, an ophthalmologist should be consulted, and CT films should be obtained to delineate the extent of the infectious process. Both retinoblastoma and battered child syndrome may present with lid edema. Typically, these children are afebrile and nontoxic in appearance. Hyphema is hemorrhage into the anterior chamber of the eye and is caused by trauma. Twenty percent of patients with neuroblastoma present with eye symptoms from metastasis. Proptosis is one of the possible presentations and can be of relatively acute onset. In general, other systemic symptoms are present and have developed more gradually.

• Question 497:

  A 3-year-old boy has had fever for 4 days. On physical examination he has bilateral cervical lymphadenopathy, injected pharynx, and dry cracked lips. A throat swab is done and the rapid strep test is negative. The child is sent home and advised to follow-up if symptoms worsen. The child is brought back 2 days later with all previous findings including a maculopapular rash, swollen hands, and conjunctivitis.

  Which of the following is the most likely diagnosis?

  A. Scarlett fever

  B. Kawasaki disease

  C. toxic shock syndrome

  D. infectious mononucleosis

  E. erythema infectiosum

  Correct Answer: B

  Centers for Disease Control and Prevention (CDC) criteria require fever of at least 5 days' duration for a clinical diagnosis of Kawasaki disease. According to these criteria, patients also must have at least four of five other findings, including bilateral conjunctival infection, one or more changes of the oral mucous membranes (e.g., pharyngeal erythema; dry, fissured, and erythematous lips; and strawberry tongue), one or more changes of the extremities (e.g., erythema, edema, and desquamation), rash, and cervical lymphadenopathy. Kawasaki disease occurs most commonly during the first 2 years of life. Thrombocytosis, rather than thrombocytopenia, is an almost invariable feature late in the course of illness. The most common serious complication of Kawasaki disease is coronary artery aneurysm formation which can result in thrombosis, aneurismal rupture, or other cardiac effects.

• Question 498:

  A 6-year-old girl has a low-grade fever, headache, and nasal congestion. She has a flushed face and has developed a lacy reticular rash on the trunk and extensor surface of her arms and legs. Palms and soles are spared. Her mother has been ill with a low-grade fever and some joint stiffness and pain. Which of the following is the most likely diagnosis?

  A. rubella

  B. measles

  C. scarlet fever

  D. roseola infantum

  E. erythema infectiosum (fifth disease)

  Correct Answer: E

  Erythema infectiosum is a common childhood viral exanthem caused by parvovirus B19. It was the fifth in a classification system of childhood exanthems; the others were rubella, measles, scarlet fever, atypical scarlet fever, and roseola infantum. The rash classically presents early with flushed cheeks or a "slapped cheek" appearance. It is followed by development of a macular erythematous rash on trunk and extremities, which then shows central clearing, developing a lacy, reticulated appearance. The infection is often not clinically apparent. Adult and older adolescents, especially females, may develop arthropathy. The symptoms are usually self-limited. Parvovirus B19 is clinically significant in people with hemolytic anemias because it may induce a transient aplastic crisis. Immunocompromised individuals are also at risk for chronic infections accompanied by anemia, neutropenia, and thrombocytopenia. It may also induce fetal demise in case of primary infection of pregnant women.

• Question 499:

  A10-year-old boy comes to the office with fever and chills for 5 days and myalgia. He has recently returned from a 2-week vacation to New England with his family. On physical examination he has mild splenomegaly. Which of the following is the most likely cause of his symptoms?

  A. Kawasaki disease

  B. pneumococcus

  C. babesiosis

  D. leptospirosis

  E. psittacosis

  Correct Answer: C

  Kawasaki disease is an acute vasculitis of unknown etiology. Humans contract brucellosis by direct contact with infected animals or by drinking unpasteurized milk. Babesiosis is transmitted by ticks. Leptospirosis is obtained from exposure to the urine of infected animals. Psittacosis is obtained from exposure to bird feces.

• Question 500:

  A 4-year-old child presents to your office in July with a history of a low-grade fever (38.1°C) and "s ores" in

  his mouth for 2 days. He has been refusing to eat but has been drinking an adequate amount of liquids.

  On examination, he is afebrile and seems well hydrated. He has ulcers on his tongue and posterior

  pharynx, which are 4 mm in diameter. You also note a few vesicles on his hands and feet, which are 34

  mm in size and mildly tender.

  Which of the following is the most likely diagnosis?

  A. herpes simplex virus (HSV)

  B. coxsackie virus

  C. aphthous ulcers

  D. Behcet syndrome

  E. traumatic ulcers

  Correct Answer: B

  Coxsackie A16 is the major cause of hand, foot, and mouth disease. This is a summer enteroviral illness presenting with classic lesions of the hand, feet, and mouth. Herpetic gingivostomatitis is the most common cause of stomatitis in children aged 13 years. There is often a high fever, fetor oris, refusal to eat, and irritability. The lesions are initially vesicular, and soon form ulcers ranging from 2 to 10 mm in diameter. The tongue, cheek, and gums are usually involved, and there may be submaxillary lymphadenitis. Aphthous ulcerations (canker sores) are painful ulcerations, which present as erythematous, indurated papules that erode to form circumscribed necrotic ulcers with gray fibrinous exudates and erythematous halo. They are 210 mm in diameter, heal spontaneously, and often recur. Behcet syndrome is a multisystem disorder characterized by recurrent oral and genital ulceration, iritis or uveitis, as well as other cutaneous, arthritic, neurologic, vascular, and gastrointestinal (GI) manifestations. It is rare in children. Traumatic oral ulcers may be seen in chronic cheek biters but do not involve extremities.