Repro USMLE step 1 9-7(13)

Question 1

This asymptomatic woman who is engaging in unprotected sex has a partner who is experiencing pain on urination and a purulent discharge from his urethra. Judging from this woman’s negative Chlamydia trachomatis swab, in conjunction with her partner’s symptoms, the partner is likely infected with Neisseria gonorrhoeae (N. gonorrhoeae). Nucleic acid amplification is now the first-line test for gonorrhea diagnosis.Culture on Thayer-Martin agar has long been considered the gold standard and is still used to evaluate antibiotic-resistant infections.

Thayer-Martin agar is a chocolate agar plate suffused with?

Answer 1

vancomycin, trimethoprim, colistin, and nystatin (VTCN)—all antibiotics that suppress the growth of endogenous flora while supporting the growth of N. gonorrhoeae . Vancomycin is an inhibitor of cell wall peptidoglycan synthesis that binds to the D-ala-D-ala part of cell wall precursors. Its purpose in the Thayer-Martin agar is to prevent the growth of gram-positive organisms such as Staphylococcus aureus.

Question 2

The majority of people (up to 60% of men and 70% of women) infected with N. gonorrhoeae are asymptomatic. However, women with asymptomatic infections are at the same risk for pelvic inflammatory disease and other complications as symptomatic women. As a result, this patient, who likely has an?

Answer 2

asymptomatic infection since she has engaged in unprotected sexual activity with her symptomatic partner, should be treated. Chlamydia often co-infects with gonorrhea, so antibiotic therapy should include coverage for both organisms. Preferred treatment includes a one-time dose of intramuscular ceftriaxone for gonorrhea and a one-time dose of oral azithromycin for Chlamydia.

Question 3

None of the other drugs named are found in Thayar-Martin agar. Doxycycline, which prevents bacterial protein synthesis from binding to the 30S ribosomal subunit, is used to treat pneumonia and other respiratory tract infections, as well as certain skin, genital (including chlamydia), intestine, and urinary system infections. Azithromycin, a macrolide antibiotic, acts by binding to the 50S ribosomal subunit; among the indications for this drug are acute bacterial exacerbations of chronic obstructive pulmonary disease, bacterial sinusitis, and otitis media, as well as other respiratory and skin infections. Penicillin prevents?

Answer 3

bacterial cell wall synthesis by binding transpeptidases, which cross-links peptidoglycan in the cell wall. It is indicated for the treatment of a range of infections; however, owing to the development of penicillin resistance in many common pathogens, including N. gonorrhoeae, its efficacy has become more limited. Among other indications, the CDC recommends use of ceftriaxone in combination with a second antibiotic as treatment for N. gonorrhoeae. Ceftriaxone is a 3rd-generation cephalosporin antibiotic that prevents bacterial cell wall synthesis by binding transpeptidases, which cross-links peptidoglycan in the cell wall.

Question 4

Men with urethritis due to Neisseria gonorrhoeae often present with dysuria and purulent urethral discharge; women with the same type of infection are usually asymptomatic. Thayer-Martin agar, which contains ?

Answer 4

vancomycin, trimethoprim, colistin, and nystatin, is the most appropriate medium for culture and diagnosis of N. gonorrhoeae infection.

Question 5

This patient presents with abnormal uterine bleeding, breast tenderness, and a painless abdominal mass. Histologic examination reveals granulosa cells arranged in a seemingly random pattern around eosinophilic fluid resembling primordial follicles, also known as Call-Exner bodies. This is a key histologic finding in the identification of granulosa cell tumors. Estrogen, which is often produced by these tumors, can cause abnormal uterine bleeding, breast tenderness, and growth of breast tissue. Androgens in the ovary are produced by theca cells, which are primarily stimulated by luteinizing hormone (LH). The androgens diffuse to the granulosa cells, which are stimulated by?

Answer 5

follicle-stimulating hormone (FSH) to convert the androgens to estrogens.

Question 6

Estrogen is a product, not a stimulant, of granulosa cells. Gonadotropin-releasing hormone stimulates ?

Answer 6

LH/FSH release from the anterior pituitary, but it does not have an effect on granulosa cells. LH stimulates theca cells, not granulosa cells. Prolactin is a pituitary hormone that stimulates milk production but does not have an effect on granulosa cells.

Question 7

Granulosa cell tumors can be diagnosed by the histologic finding of Call-Exner bodies. These tumors often produce estrogen, which is stimulated by ?

Answer 7

the production of FSH.

Question 8

Advanced maternal age is a risk factor for genetic fetal abnormalities. In this 37-year-old patient, prenatal maternal serum screening reveals a constellation of low serum AFP, low unconjugated estriol, low β-HCG, and normal inhibin A, indicative of a fetus with?

Answer 8

trisomy 18, otherwise known as Edwards syndrome. Clinically, Edwards syndrome presents with prominent occiput, rocker-bottom feet, intellectual disability, clenched fists, low-set ears, micrognathia, and congenital heart disease. Mortality within the first year of life is common. Trisomies are usually the result of nondisjunction of chromosomes during meiosis; in Edwards syndrome, it is the nondisjunction of chromosome 18. Nondisjunction describes unequal division during meiosis I, resulting in one cell receiving three sets of the same chromosome and one cell receiving only one set of that chromosome. The diagnosis of trisomy 18 can be confirmed by means of amniocentesis along with a fetal karyotype.

Question 9

The other abnormalities are inconsistent with the laboratory profile obtained for this patient. Three of these abnormalities are not diagnosed by maternal serum markers: a 22q11 microdeletion, which results in DiGeorge syndrome; a 5p deletion, which results in cri-du-chat syndrome (requires amniocentesis or clinical diagnosis in infancy); and maternal and paternal uniparental disomy of?

Answer 9

chromosome 15, which cause Prader-Willi and Angelman syndromes, respectively.
Two cytogenetic abnormalities can be identified on prenatal screening. However, findings that are specific to these conditions differ from those associated with nondisjunction of chromosome 18, as summarized in the table. These include nondisjunction of chromosome 13, which results in Patau syndrome and involves normal levels of AFP and estriol, and nondisjunction of chromosome 21, resulting in trisomy 21 (Down syndrome), which is associated with elevated levels of β-hCG and inhibin A.

Question 10

Advanced maternal age is a risk factor for genetic fetal abnormalities, in particular trisomies, which can be screened for by determining levels of AFP, unconjugated estriol, β-hCG, and inhibin A. Low levels of AFP, unconjugated estriol, and β-hCG with a normal inhibin level suggest the possibility of ?

Answer 10

trisomy 18 (Edwards syndrome).

Question 11

This patient is experiencing dyschezia (painful defecation), dyspareunia (pain during sexual intercourse), and dysmenorrhea (painful menstruation). As the physician has noted, the physical exam findings of nodularity along the uterosacral ligament, in association with her symptoms, point to a diagnosis of endometriosis. This condition is characterized by the presence of endometrium-like glands and stroma outside the uterus. Endometriosis is most commonly found in the ovaries, followed by ?

Answer 11

the anterior and posterior cul-de-sac (also known as the rectouterine pouch), broad ligaments, uterosacral ligaments, uterus, fallopian tubes, sigmoid colon, appendix, and round ligaments. These sites are highlighted in the illustration. This patient’s difficulty on defecation suggests that the ectopic tissue is present in the posterior cul-de-sac, as this site is closest to the colon.

Question 12

Complications of endometriosis consist of bowel and ureteral obstruction resulting from pelvic adhesions. Ectopic endometrial glandular tissue is influenced by ovarian hormones and undergoes cyclic bleeding. The earliest visible manifestations of endometriosis are whitish peritoneal plaques. Endometriosis can be observed laparoscopically as small subserosal nodules with a brown appearance. Over time the repeated hemorrhaging can produce extensive fibrosis surrounding the endometrial tissue, which can result in adhesions to adnexal structures or to bowel and can obliterate the posterior pelvic cul-de-sac (pouch of Douglas).
The cervix is not commonly involved in ?

Answer 12

endometriosis and is seen in fewer than 1% of cases. Ectopic tissue in the fallopian tubes would not cause dyschezia, as this is not the closest site to the colon. The ovaries are the most common sites for ectopic tissue in endometriosis, but this patient’s presentation points more towards the posterior cul-de-sac. The uterus is the normal location of the endometrium and is not considered to have ectopic endometrial tissue.

Question 13

Although the ovaries are the most common site of ectopic tissue in endometriosis, ectopic tissue can be found in other sites such as?

Answer 13

the posterior cul-de-sac, where it may cause dyschezia, along with dysmenorrhea and dyspareunia.

Question 14

This woman, who presents with severe lower abdominal pain, fever, and tachycardia during labor, has been diagnosed with endometritis, an inflammation due to infection of the uterine lining. Endometritis infection is usually polymicrobial and anaerobic. Although endometritis can be associated with sexually transmitted infections, in this case, the condition is the result of prolonged rupture of the membranes. The patient’s acutely increased creatinine level after antibiotic treatment suggests that a nephrotoxic drug was used. The antimicrobial management of endometritis includes?

Answer 14

gentamicin and clindamycin with or without ampicillin.

Gentamicin is an aminoglycoside that is used to treat severe gram-negative rod infections. Toxicities include nephrotoxicity, ototoxicity, and teratogenicity. Aminoglycosides are bactericidal and act by inhibiting the formation of the initiation complex by binding to the 30S ribosomal unit and causing misreading of messenger RNA. Because they require oxygen for uptake, aminoglycosides are ineffective against anaerobes.

Question 15

Vancomycin is associated with nephrotoxicity; however, it is not commonly used in the management of endometritis.
Aztreonam is usually not associated with serious adverse effects, although it can cause rash, phlebitis, and gastrointestinal upset.
Fluconazole is an antifungal agent that causes headache, nausea, and abdominal pain.
Tetracycline binds?

Answer 15

calcium and other metallic ions, causing discoloration of teeth and inhibition of bone growth, as well as photosensitivity.

Question 16

Gentamicin, an aminoglycoside, is known to be potentially nephrotoxic, ototoxic, and teratogenic. In the treatment of endometritis, gentamicin may be used in combination with?

Answer 16

clindamycin with or without ampicillin.

Question 17

This patient presents with severe abdominal cramping, menorrhagia, and lower back pain correlating with her menstrual cycle. Her symptoms, which have not responded to treatment with oral contraceptives, are classic for endometriosis. Diagnosis would be confirmed by biopsy of the ovarian lesions showing ectopic endometrium.

Ectopic endometrium is estrogen-dependent. Sex hormones are generally produced in response to follicle-stimulating hormone (FSH) and luteinizing hormone (LH), which are controlled by physiologic pulsatile secretion of gonadotropin-releasing hormone (GnRH). Treatment with GnRH agonists like leuprolide or goserelin removes this physiologic pulsation and actually decreases LH/FSH secretion after a short stimulatory period, thereby inhibiting growth of endometrial tissue.
Major adverse effects of GnRH-induced sex hormone depletion include?

Answer 17

osteoporosis and pseudo-menopause (night sweats, hot flashes, etc). Although GnRH agonists are more commonly used, danazol, a synthetic androgen, can also be used to treat endometriosis, Of note, when the ovaries are involved in endometriosis, disease is seen bilaterally in approximately one third of cases.

Question 18

Heart failure can be an adverse effect of trastuzumab, a monoclonal antibody used to treat HER2-positive breast cancer. Hyperkalemic metabolic acidosis may occur in patients taking spironolactone, a diuretic that is used to treat high blood pressure, heart failure, and edema. (This drug may also be used off-label to treat hirsutism in women with polycystic ovarian syndrome.) Increased uterine cancer risk is seen with estrogen-only supplementation, which may be taken to?

Answer 18

alleviate menopause-related symptoms. Stevens-Johnson syndrome is one adverse effect of aromatase inhibitors, used in the treatment of breast cancer in postmenopausal women.

Question 19

GnRH agonists such as leuprolide or goserelin can be used for treatment of endometriosis-related pelvic pain. They act by decreasing LH/FSH secretion after a short stimulatory period. Adverse effects of sex hormone depletion include osteoporosis and pseudo-menopause. Danazol can also be used to treat ?

Answer 19

endometriosis, but GnRH agonists are more commonly used.

Question 20

This patient’s absence of erections during periods of rapid eye movement (REM) and morning tumescence, indicates that his symptoms are pathologic, not psychological, and that he requires pharmacologic treatment for erectile dysfunction. Sildenafil is a first-line treatment for this condition. The drug acts by?

Answer 20

inhibiting cGMP phosphodiesterase, which increases cGMP levels via direct release of nitric oxide (NO), thus leading to smooth muscle relaxation in the corpus cavernosum. Smooth muscle relaxation allows increased blood flow to the corpus vascularity.

Some of sildenafil’s adverse effects include headache, flushing, and disturbances in color vision. Sildenafil is contraindicated in patients taking nitroglycerin or other nitrates because it enhances their effect.

Question 21

Activation of cGMP phosphodiesterase breaks down nitric oxide, resulting in reduced blood flow to the corpus cavernosum and subsequent loss of erection. Androgen supplementation is rarely effective in the setting of erectile dysfunction, because most patients with this condition have normal testosterone levels; moreover, adverse effects include decreased spermatogenesis, gynecomastia, and possible impotence. Alprostadil is an intraurethral prostaglandin pellet that increases?

Answer 21

arterial inflow and decreases venous outflow, thereby increasing erection by binding G proteins and stimulating adenylyl cyclase. However, this would not be the first-line oral agent for this condition. Sildenafil does not directly increase NO levels, but, instead, prolongs response to NO.

Question 22

The first-line treatments for erectile dysfunction are phosphodiesterase-5 inhibitors such as sildenafil, which increases cGMP levels by?

Answer 22

inhibiting the degradation of cGMP to GMP by phosphodiesterase, prolonging cGMP action.

Question 23

A woman with a 2-year-old son comes to her physician because she has been unable to conceive a second child for more than a year. The woman is currently breastfeeding her son.
Which of the following best explains the physiologic mechanism currently preventing her from getting pregnant?

Answer 23

Prolactin directly inhibits the secretion of GnRH from the hypothalamus, which results in a decrease in LH and FSH secretion and thus prevents ovulation.

Question 24

This patient is a 52-year-old woman who presents with amenorrhea (last menstrual period was 12 months ago) and hot flashes (heat with sweating and rapid heartbeat). Examination reveals decreased vaginal rugae and dryness. These are classic symptoms of menopause, which in the United States commonly occurs around age 51. Menopause is the cessation of estrogen production secondary to the age-linked decline in the number of ovarian follicles. Complications of menopause include hot flashes, vaginal atrophy, and osteoporosis (all due to decreasing levels of estrogen), as well as an increased risk of coronary artery disease. HRT increases bone mineral density and decreases the risk of?

Answer 24

osteoporotic fractures; the mechanism of decreased bone loss is estrogen’s inhibition of osteoclastic bone resorption. However, it should be noted that HRT has serious adverse effects.

Question 25

A boy is born with ambiguous external genitalia. Physical examination reveals a bifid scrotum and hypospadias. The attending explains to the concerned parents that their child may be suffering from a hormonal deficiency that leads to defective development of the genital tubercle.

Which of the following is the adult male counterpart of the genital tubercle in the embryo?

Answer 25

With normal development in the male, under the influence of dihydrotestosterone, the genital tubercle develops into the glans penis. The glans penis is the head of the penis and contains the external urethral orifice. In the female, the genital tubercle develops into the clitoris.

In males, the urogenital sinus develops into the prostate and bulbourethral glands. The ventral shaft of the penis is formed from urogenital fold fusion. The scrotum develops from the labioscrotal swellings.

Question 26

The woman presents during the first trimester of her fifth pregnancy; each of her previous pregnancies ended in miscarriage during the first trimester. The accompanying pathologic specimen demonstrates a uterus with indented fundus and separation of uterine horns, which is pathognomonic for a bicornuate uterus.

Although male and female fetuses are genetically different from the moment of conception, sex differentiation does not begin until around the eighth week of development, when the gonads secrete hormones that influence?

Answer 26

the development of either the paramesonephric ducts in the female or the mesonephric ducts in the male. In the absence of the testis-determining factor located on the Y chromosome, the mesonephric ducts begin to degenerate and form a matrix for the developing paramesonephric ducts. The paramesonephric ducts fuse at their inferior margin, forming the single lumen of the uterovaginal canal. Failure of fusion of the paramesonephric ducts can result in a bicornuate uterus, as shown in the image. This anatomic variation is associated with recurrent pregnancy loss.

Question 27

This man, who has a history of benign prostatic hyperplasia, is found to have an elevated PSA level of 11.2 ng/mL (up from 6.4 ng/mL at his last annual examination). Although using levels of PSA to help diagnose malignancy of the prostate is controversial, it is generally thought that a rapid increase in PSA over the course of a year warrants further consideration.

As seen in the image below, the prostate gland is divided into several anatomic zones. In about 75% of cases, prostate cancer is present in?

Answer 27

the peripheral zone, usually arising near the rectum. This explains why a digital rectal examination is a useful screening test. The peripheral zone has a different embryologic derivation from the transition zone, which is the most common site of benign prostatic hyperplasia.

The central zone, which surrounds the ejaculatory duct, is an uncommon location for prostate cancer. The periurethral zone and the transitional zone are synonymous and are the most common sites of benign prostatic hyperplasia but are uncommon sites for cancer.
Finally, the seminal vesicles, while located adjacent to the prostate, are not made of prostatic tissue and therefore are not a site of origin for prostate cancer.

Question 28

NSAID use, as seen in this patient, can cause gastric ulcers through inhibition of prostaglandin production in the gastrointestinal (GI) tract, where prostaglandins help promote bicarbonate secretion and production and secretion of the mucous barrier, while reducing acid secretion. Misoprostol is a prostaglandin E1 analog that restores the action of prostaglandins in the GI tract, resulting in reduced secretion of gastric acid and increased production and secretion of the gastric mucous barrier. This characteristic makes the drug useful in decreasing the incidence of NSAID-induced peptic ulcers in patients with concomitant long-term use of NSAIDs. As a prostaglandin, misoprostol causes uterine cramps and is contraindicated in women of childbearing potential because of its abortifacient properties. In fact, misoprostol is frequently used for medical termination of pregnancy (in conjunction with mifepristone). Misoprostol has also been used off-label to induce?

Answer 28

cervical effacement (ripening) and labor. Other common adverse effects of misoprostol are diarrhea, nausea, and vomiting.

There is no current evidence that prostaglandins, such as misoprostol, can cause intrauterine growth restriction, neural tube defects, polyhydramnios, or closure of the of ductus arteriosus (In fact, prostaglandins are used to keep the ductus arteriosus patent in many patients with cardiovascular anomalies.) Although misoprostol can cause diarrhea after prolonged use, this is not a reason that it would be contraindicated for a pregnant woman.

Question 29

This child is beginning to babble but cannot yet talk. He is able to pull himself up but still needs assistance to walk, and he displays a pincer grasp. He also shows stranger anxiety. This child is most likely <15 months old because he cannot walk unassisted. Stranger anxiety usually begins at 7–9 months, with sound imitation beginning at this stage or later. The pincer grasp (grasping an object with index finger and thumb) also usually develops by 10 months of age. His ability to stand and walk with assistance (gross motor skills) suggest?

Answer 29

that he is at least 10 months old but likely no older than 12 months. An upward moving great toe with fanning of the other toes when the bottom of the foot is stroked describes the Babinski sign, which is seen in children before 12 months of age. The Babinski sign is a normal finding in an infant and indicates that the corticospinal pathways are not fully myelinated. In adults, this is a pathologic finding, indicative of an upper motor neuron lesion.

Question 30

By the age of 4 months, an infant will orient only to voice, not to name and gesture. Rolling and sitting, but not crawling, are characteristic of an infant at around 6 months of age. Stacking 6 cubes is characteristic of a child at around?

Answer 30

2 years of age. A child of around 3 years of age can ride a tricycle. Self-feeding with a fork and spoon is characteristic of a child at around 20 months of age.

By the age of 4 months, an infant will orient only to voice, not to name and gesture. Rolling and sitting, but not crawling, are characteristic of an infant at around 6 months of age. Stacking 6 cubes is characteristic of a child at around 2 years of age. A child of around 3 years of age can ride a tricycle. Self-feeding with a fork and spoon is characteristic of a child at around 20 months of age.