USMLE USMLE Certifications USMLE-STEP-1 Questions & Answers

• Question 271:

  During a routine physical examination, a 16-year-old boy is found to have only minimal secondary sexual development, gynecomastia, and a tall, eunuchoid habitus. Achromosomal determination on this individual would most likely reveal which of the following?

  A. 45, XO

  B. 45, YO

  C. 46, XX

  D. 46, XY

  E. 47, XXY

  F. 47, XYY

  Correct Answer: E

  Section: Pathology and Path physiology The physical description of this boy is that of Kleinfelter syndrome. This condition is not usually diagnosed until after puberty when the secondary sexual characteristics do not develop normally. Most of these individuals are 47, XXY but some may have additional X or Y chromosomes. 45, XO (choice A) is characteristic of a female with Turner syndrome which is usually diagnosed early in life. 45, YO (choice B) is not compatible with life and is not seen. 46, XX (choice C) is the chromosome number of a normal female and 46, XY (choice D) is that of a normal male. Males with 47, XYY (choice F) are above average in height and have an increased incidence of developing severe acne. IQ is normal but there may be mild learning disabilities.

• Question 272:

  A 66-year-old man presents with a 3-month history of intermittent dysphagia that has now become constant and is accompanied by pain and some weight loss. X-rays of the esophagus with barium swallow show structural and filling defects, and reduced peristalsis. Abiopsy is taken and is shown in below figure. The best diagnosis is which of the following?

  

  A. adenocarcinoma of the esophagus

  B. Barrett esophagus

  C. Candida esophagitis

  D. fibrous stricture of the esophagus

  E. squamous cell carcinoma of the esophagus

  Correct Answer: E

  Section: Pathology and Path physiology The cells in figure are pleomorphic and invasive indicating their malignant character. Additionally, there are many intercellular bridges ("prickles") joining the cells indicating their squamous origin. Therefore, this is a squamous cell carcinoma. The presentation described is fairly typical for squamous cell carcinoma of the esophagus. Its development is closely associated with the risk factors of smoking and alcoholism. Adenocarcinoma of the esophagus (choice A) arises in the lower esophagus in a background of Barrett esophagus and is, of course, composed of malignant glandular cells, not the squamous cells seen here. Barrett esophagus (choice B) demonstrates metaplastic glandular epithelium. Candida esophagitis (choice C) is recognized by the presence of yeast and pseudohyphae. Fibrous stricture (choice D) can be caused, for example, by severe chronic reflux from ingestion of corrosives and produces fibrosis. Lye ingestion is associated with a 1000-fold increase in risk for squamous cell carcinoma.

• Question 273:

  On otoscopic examination, a patient is found to have a 2-cm mass protruding from a retraction pocket in his right tympanic membrane. The lesion is removed and determined to be a cystic mass lined by squamous epithelium containing desquamated cellular debris and a mononuclear infiltrate. Which of the following is the most likely cause of this lesion?

  A. barotraumas

  B. chronic otitis media

  C. exostosis formation in the external auditory canal

  D. squamous cell carcinoma of the external auditory canal

  E. tympanosclerosis

  Correct Answer: B

  Section: Pathology and Path physiology A cholesteatoma is a cystic lesion lined by squamous epithelium and containing keratinaceous material. It is most probably formed by the protrusion of squamous epithelium from the middle ear canal through a perforation in the eardrum that was itself the result of chronic otitis media. Barotrauma (choice A) to the ear can be produced by sudden changes in atmospheric pressure compared to the relatively low middle ear pressure. This results in inflammation of the mucous membrane of the middle ear (serous otitis media). Exostosis formation in the external auditory canal (choice C) refers to the growth of a bony swelling that may occur with chronic exposure to cold water. Squamous cell carcinomas of the external auditory canal (choice D) are unusual and have a histological appearance similar to other squamous cell carcinomas (polygonal cells with prickles and pearls), which is quite different from the description given. Tympanosclerosis (choice E) of the tympanic membrane results from resolved acute otitis media producing acellular hyaline and calcific deposits in the tympanic membrane.

• Question 274:

  A2-month-old girl with a history of persistent physiologic jaundice following birth is now reported by her parents to sleep excessively and display little activity. Physical examination reveals abnormal deep tendon reflexes, hypothermia, and muscular hypotonia. Based on this information, which of the following would be the best therapy for her condition?

  A. antibiotics

  B. growth hormone

  C. thiamine

  D. thyroxine

  E. vitamin D

  Correct Answer: D

  Section: Pathology and Path physiology This infant has cretinism, a condition caused by a neonatal lack of thyroxine. Thyroid agenesis, iodine deficiency, ingestion of goitrogens, and hereditary enzymatic deficiencies may all result in a relative lack of biologically active thyroxine. Affected children may display lethargy, jaundice, hypothermia, muscular hypotonia, and mental retardation. Medicinal replacement of thyroxine is therapeutic. The mental retardation may not be reversible, however, unless treated early. Antibiotics (choice A) have no effect in treating cretinism. Growth hormone (choice B) is an effective treatment for pituitary dwarfism but it has no benefit in cretinism. Treatment with thiamine (choice C) is the appropriate therapy for beriberi, not cretinism. A lack of vitamin D (choice E) causes rickets, not cretinism.

• Question 275:

  A 28-year-old woman has an ultrasound examination during the second trimester of her third pregnancy. She is found to have greatly decreased amniotic fluid but the fetus appears to be the appropriate size for the gestational age. Her two previous pregnancies produced normal-term infants. The family history is otherwise unremarkable. Which of the following conditions most likely explains these findings?

  A. bilateral cystic renal dysplasia

  B. bronchopulmonary dysplasia

  C. hypoplasia of the lungs

  D. Klinefelter syndrome

  E. placenta previa

  Correct Answer: A

  Section: Pathology and Path physiology Most of the amniotic fluid is derived from the urine of the fetus. In a fetus with bilateral cystic renal dysplasia, little or no urine is being produced, which leads to the oligohydramnios seen in this case. Bronchopulmonary dysplasia (choice B) may be seen in babies who have respiratory distress syndrome and are given oxygen therapy. Hypoplasia of the lungs (choice C) is a consequence of oligohydramnios because inhalation of amniotic fluid by the fetus is necessary for normal lung development. Klinefelter syndrome (choice D) occurs in males with XXY karyotype and does not explain the findings in this case. Placenta previa (choice E) occurs when there is abnormally low implantation of the fertilized ovum in the uterus such that it overlies the internal os.

• Question 276:

  A 73-year-old man with a history of an MI 2 years ago has been experiencing gradually increasing shortness of breath over the past 4 weeks. Physical examination reveals bilateral crackles on pulmonary auscultation and 2+ pitting edema of the lower legs bilaterally. Which of the following most likely occurred in this patient to produce these changes?

  A. interventricular septal wall thickening

  B. lobar pneumonia

  C. new MI

  D. spontaneous idiopathic pneumothorax

  E. ventricular aneurysm rupture

  Correct Answer: C

  Section: Pathology and Path physiology Bilateral crackles on lung auscultation and 2+ pitting edema of the bilateral lower extremities are signs of left-sided and right-sided congestive heart failure, respectively. The only logical choice that could lead to both in this patient is an MI, where left ventricular failure subsequently leads to right ventricular failure. Interventricular septal wall thickening (choice A) is a particular characteristic of idiopathic hypertrophic cardiomyopathy, and frequently causes outflow tract obstruction during systole. It is an autosomaldominant genetic disease leading to serious progressive cardiac abnormalities typically beginning in young adulthood, and is a common cause of sudden, otherwise unexplainable, death in young athletes. While lobar pneumonia (choice B) is common in older patients, and could lead to shortness of breath, it would not be associated with right heart failure and bilateral lower extremity edema. Similarly, a spontaneous idiopathic pneumothorax (choice D) may also result in shortness of breath, but does not cause right heart failure; this phenomenon is most commonly encountered in young individuals, not an older population. Ventricular aneurysms (choice E) occur as a possible complication of extensive transmural anteroseptal MIs in which a large area of thin scar tissue produces external bulging; they are not associated with rupture.

• Question 277:

  A 34-year-old woman has a history of menorrhagia. Within the wall of her uterus are several solid nodules of various sizes. The histological appearance of one of the nodules is depicted in below figure. These nodules represent which of the following?

  

  A. adenomyosis

  B. Krukenberg tumors

  C. leiomyomas

  D. metastatic malignancy

  E. Ovarian ectopias

  Correct Answer: C

  Section: Pathology and Path physiology Figure displays interweaving bundles of smooth muscle cells, which, as a discrete myometrial nodule, define a leiomyoma. These are common tumors that may be asymptomatic or produce menorrhagia. Gross appearance is that of a solid white nodule. Adenomyosis (choice A) may clinically and grossly mimic leiomyomas. Adenomyosis, however, has a triphasic microscopic appearance consisting of benign endometrial glands, benign endometrial stroma, and smooth muscle hypertrophy. AKrukenberg tumor (choice B) is replacement of the ovary by metastatic GI adenocarcinoma. The diagnosis of metastatic malignancy (choice D) is not supported by the photomicrograph of a benign process. Ovarian ectopia (choice E) is exceedingly rare and is incompatible with the histology of the photomicrograph.

• Question 278:

  A 36-year-old man is now in his third year of steroid therapy since being diagnosed with a systemic vasculitis. Prior to initiating treatment in the acute phase of the disorder, he underwent a biopsy of a medium-sized artery. This biopsy specimen displayed fibrinoid necrosis of the media accompanied by a transmural acute inflammatory infiltrate. Significant negative clinical findings included a normal aortic arch, absence of giant cells in the artery biopsy, normal upper airway examination, and no history of tobacco use. Which of the following disorders best correlates with these findings?

  A. Kawasaki disease

  B. polyarteritis nodosa

  C. Takayasu disease

  D. temporal arteritis

  E. thromboangiitis obliterans

  Correct Answer: B

  Section: Pathology and Path physiology Polyarteritis nodosa is a systemic vasculitis primarily seen in young adult males. Fibrinoid necrosis and acute inflammation are seen microscopically in the acute phase. Mucocutaneous lymph node syndrome (Kawasaki disease) (choice A) is a childhood disorder with coronary vasculitis, cervical lymphadenopathy, and acute onset. Takayasu disease (choice C) is characterized by fibrosis of the upper aorta. The classic patient is a Japanese woman with HLA-DR4. Temporal or giant cell arteritis (choice D) is a granulomatous arterial inflammation seen in the elderly. The superficial temporal and intercranial arteries are preferentially involved. Thromboangiitis obliterans (choice E) is an occlusive disease of small arteries strongly related to cigarette smoking

• Question 279:

  A 45-year-old man is bitten by a poisonous snake the venom of which triggers the release of thromboplastin in his circulation. Which of the following would you most expect to see as a consequence of this event?

  A. abnormal neutrophilic degranulation resulting in small vessel vasculitis and subsequent hemorrhage or thrombosis

  B. deposition of antigen-antibody complexes in various tissue beds, causing vasculitis with thrombosis, glomerulonephritis, and arthritis

  C. formation of multiple, migratory peripheral venous thromboses without evidence of tissue ischemia or hemorrhage

  D. immediate mast cell degranulation of vasoactive amines followed by progressive vascular leakage and subsequent tissue ischemia

  E. widespread development of thrombi in the microvasculature followed by hemorrhage

  Correct Answer: E

  Section: Pathology and Path physiology Thromboplastin-like substances (or tissue factor) released into the circulation can initiate disseminated intravascular coagulation (DIC). In this situation, thromboplastin activates the coagulation cascade, leading to the formation of multiple thrombi distributed throughout the microvasculature. As this process progresses, platelets and coagulation factors are consumed and hemorrhage can occur; bleeding is exacerbated by activation of the fibrinolytic system. Abnormal neutrophilic degranulation resulting in small vessel vasculitis and subsequent hemorrhage or thrombosis (choice A) is an example of a type II hypersensitivity reaction associated with circulating antineutrophil cytoplasmic antibodies (ANCA); examples of ANCA-associated vasculitides include Wegener granulomatosis and Churg-Strauss syndrome. Deposition of antigen-antibody complexes in various tissue beds, causing vasculitis with thrombosis, glomerulonephritis, and arthritis (choice B) describes a nonspecific systemic type III hypersensitivity response (which takes several days to develop). Formation of multiple, migratory peripheral venous thromboses without evidence of tissue ischemia or hemorrhage (choice C) refers to igratory thrombophlebitis, a condition associated with certain types of cancers, particularly adenocarcinomas in which hypercoagulability occurs as a paraneoplastic syndrome; this is referred to as Trousseau syndrome. These and other tumors are also independently capable of initiating DIC. Immediate mast cell degranulation of vasoactive amines followed by progressive vascular leakage and subsequent tissue ischemia (choice D) describes anaphylaxis, a type I hypersensitivity reaction.

• Question 280:

  A 35-year-old lifeguard requests a consultation for a lesion on his upper back that his girlfriend first noticed about a year ago. He states that he is more concerned since it has increased in size. Your examination reveals a 15 ?16 mm raised nodule with irregular borders and variable areas of dark and light pigmentation. This most likely represents which of the following?

  A. actinic keratosis

  B. compound nevus

  C. Lentigo simplex

  D. malignant melanoma

  E. seborrheic keratosis

  Correct Answer: D

  Section: Pathology and Path physiology Askin lesion that is >10 mm, increasing in size, has variable pigmentation, and irregular borders elicits extreme concern and is most probably a malignant melanoma. Actinic keratoses (choice A) are potentially premalignant skin lesions that, as the name suggests, are the result of chronic sun exposure; they are typically <1 cm in diameter. The accumulation of keratin on the surface imparts a rough or scaly texture to the skin. Compound nevi (choice B) (moles) develop when nests of nevi cells (modified melanocytes) extend from the dermoepidermal junction (junction nevus) into the underlying dermis; they are typically brown or flesh-colored, raised, dome-shaped lesions that are symmetrical and uniform. Lentigo simplex (choice C) refers to a benign focal hyperplasia of melanocytes; lesions typically appear as small (<1 cm) brown, sharply defined, oval macules. They have no predisposition to neoplastic change. Seborrheic keratoses (choice E) are benign pigmented skin tumors that are usually found on older individuals; lesions are flat, round waxy plaques that may seem to be glued on to the skin. Close inspection reveals pore-like structures with keratin plugs which helps to differentiate them from melanomas. These lesions have no malignant potential, but the sudden appearance of multiple lesions could be a paraneoplastic syndrome indicating a visceral malignancy (sign of Leser-Tr閘at).