Repro USMLE step 1 9-6 (11

Question 1

In the case of globozoospermia (sperm with round heads), the Golgi apparatus is not transformed into the acrosome, resulting in male infertility. Correction of the transformation of the Golgi apparatus into the acrosome allows spermatids to complete spermiogenesis, which is the series of postmeiotic morphologic changes that marks the final maturation of the sperm. Spermatids are ?

Answer 1

the 23 (1N, 1C) cells that are formed from secondary spermatocytes after meiosis II is completed. They undergo morphologic changes to become mature sperm that include acrosome, head, neck, and tail.

Question 2

At no point during male gametogenesis is there a haploid cell with 46 chromosomes.
Both primordial germ cells in the testes, which are dormant until puberty, and type A spermatogonia, which develop at puberty, are ?

Answer 2

46 (2N, 2C) cell types. A type A spermatogonium perpetuates itself to provide a constant supply of sperm cells; it also differentiates into type B spermatogonia.
Primary spermatocytes are 46 (2N, 4C) cells that result from the DNA replication of type B spermatogonia.

Question 3

Secondary spermatocytes are?

Answer 3

23 (1N, 2C) cells that result from primary spermatocytes completing meiosis I. Each primary spermatocyte forms two secondary spermatocytes, each going on to form two spermatids.

Question 4

Spermiogenesis is the period following the completion of meiosis where the cells undergo morphologic changes and final maturation. During this stage, the cells each have?

Answer 4

23 chromosomes, and they are haploid (1N).

Question 5

This patient is manifesting signs of secondary syphilis (eg, fever, diffuse rash, genital lesions consistent with the condyloma lata), which typically occurs approximately 6 weeks after the painless chancre of primary syphilis has healed. This stage is characterized by widespread rash, generalized lymphadenopathy, fever, and multiorgan involvement. The “small, wart-like lesions” on the patient’s scrotum are called condylomata lata; such lesions often appear moist, flat-topped, and white. Although dark-field microscopy of a specimen from an active lesion may yield the suspected diagnosis of?

Answer 5

syphilis, the fluorescent treponemal antibody absorption (FTA-ABS) test is the most specific serologic test to confirm the diagnosis of syphilis caused by Treponema pallidum.

Question 6

Most patients, however, will typically undergo venereal disease research laboratory (VDRL), toluidine red unheated serum test (TRUST), or rapid plasma reagin (RPR) testing initially. If test results are positive, diagnosis will be confirmed by ?

Answer 6

the FTA-ABS test, because it is the most specific test. Compared with the VDRL test, the FTA-ABS test results also turn positive earlier in the disease course and remain positive longer.
The TRUST, RPR, and VDRL tests are each used to screen for syphilis because they have high sensitivity but are relatively nonspecific. The Weil-Felix reaction test screens for Rickettsia infections, not for Treponema pallidum.

Question 7

The most specific test used to diagnose syphilis is ?

Answer 7

the FTA-ABS test. The TRUST, RPR, and VDRL tests each yield higher rates of false-positive test results.

Question 8

Krukenberg tumors are cancer metastases to the ovaries that are described as mucin-secreting “signet-ring” cells. In most of the cases (up to 70%), the primary site of Krukenberg tumors occurs in the stomach. Examples of other less common primary sites of Krukenberg tumors are the colon, appendix, and breast. Stomach cancer is often an adenocarcinoma that can spread aggressively to lymph nodes and the liver. A classic sign of metastatic stomach cancer is ?

Answer 8

involvement of the left supraclavicular lymph node, called Virchow node. Involvement is on the left side because the thoracic duct drains all structures on the left in the thoracic cavity and all structures below the diaphragm on both sides.

Question 9

Hematochezia is bright red, bloody stool and is often an early sign of colorectal carcinoma. Risk factors for colorectal carcinoma include villous adenomatous polyps, inflammatory bowel disease, low-fiber diet, familial adenomatous polyposis, hereditary nonpolyposis colorectal cancer, and a positive family history. Hematochezia is not associated with ?

Answer 9

stomach or ovarian cancers. Colorectal carcinomas usually metastasize to the liver.

Question 10

Galactorrhea is leakage from the breasts that is not associated with normal lactation but is associated with elevated prolactin levels secondary to prolactinomas in the anterior pituitary. Prolactin stimulates breast development and milk production while also inhibiting ovulation and spermatogenesis by inhibiting the release of gonadotropin-releasing hormone and subsequently suppressing luteinizing and follicle-stimulating hormones. Galactorrhea is not associated with stomach or ovarian cancers. Prolactinomas rarely metastasize.
A palpable, nontender gallbladder (Courvoisier sign) is associated with distal common bile duct obstruction secondary to pancreatic adenocarcinoma. Other signs and symptoms of pancreatic cancer include?

Answer 10

abdominal pain radiating to the subscapular area, weight loss, anorexia, and migratory thrombophlebitis (Trousseau syndrome). A palpable gallbladder is not associated with stomach or ovarian cancers.

Question 11

Basal cell carcinoma (BCC) often presents as “pearly papules” on sun-exposed areas, such as the face and arms. Papules are not associated with stomach or ovarian cancers. BCC is locally invasive but almost never metastasizes.
Bilateral, mucin-secreting “signet ring” cells in the ovaries is suggestive of stomach adenocarcinoma metastasis. An early sign of gastrointestinal carcinoma in some patients is?

Answer 11

Virchow node, an enlarged left supraclavicular node.

Question 12

This patient presents with a month-long history of sore throat, fatigue, low-grade fever, and malaise. In the setting of nonpruritic, red, discrete macules that progress to papular lesions, secondary syphilis is the most likely diagnosis. These lesions are classically found on the soles and palms; other signs of secondary syphilis include condylomata lata (present in only 10% of patients), and silver-gray genital lesions with surrounding erythema. It is the presentation and location of these skin lesions that make syphilis the most likely cause of the patient’s current symptoms.

Primary syphilis typically presents as?

Answer 12

a painless, single papule (known as a chancre) that can often go unnoticed by women because the primary site is on the labia or cervix. Left untreated, secondary syphilis can enter the latent phase; approximately 33% of patients will progress from the latent phase to tertiary syphilis. In tertiary syphilis, the presentation includes gummatous syphilis, cardiovascular syphilis, or neurosyphilis.

Question 13

Cardiovascular syphilis can occur in 10% of untreated patients, and characteristically results in an aortic arch or ascending aortic aneurysm, caused by destruction of the vasa vasorum and subsequent necrosis of the media layer of the aorta. Aortic aneurysms that include the aortic root can cause aortic insufficiency due to dilation of the aortic valve ring that often results in aortic infarction.
AIDS is the the most advanced stage of HIV infection and is diagnosed with a?

Answer 13

CD4+ count <200. Patients with AIDS often present with increased susceptibility to minor infections. This patient shows no signs of a compromised immune system.
Cervical carcinoma is secondary to HPV infection and is localized to the cervix without any major generalized lymphadenopathy or malaise, as seen in this patient. This patient’s genital lesions and those seen on her palms, are typical of a rash, not of verrucae (warts).

Question 14

Perihepatitis, also called Fitz-Hugh-Curtis syndrome, is a complication of pelvic inflammatory disease, and usually presents with right upper quadrant pain. In women, it is closely associated with pelvic inflammatory disease caused by chlamydia or gonorrhea. A rash is not typically associated with this condition.
Pelvic inflammatory disease is a complication of ?

Answer 14

uncontrolled gonorrhea, chlamydia, or vaginosis. It presents with severe adnexal tenderness. Cutaneous lesions on the extremities are not pathognomonic for this disease, but are associated with secondary syphilis.

Question 15

Secondary syphilis can present with widely distributed nonpruritic, red, discrete, macules that are classically seen on the palms and soles, but may also appear on the trunk or proximal extremities. Other common symptoms and signs include?

Answer 15

low-grade fever, sore throat, generalized lymphadenopathy, malaise, condylomata lata, and silver-gray mucosal lesions. Syphilis can cause skin, bone, liver, testes, neurological, and cardiovascular complications–including aortic infarctions.

Question 16

This infant has multiple irregularities including abnormalities of the skull and facial features, growth deficiency, underdeveloped nails of the fingers and toes, cleft lip, and microcephaly. The infant’s features are consistent with fetal hydantoin syndrome due to maternal use of antiepileptic drugs, such as?

Answer 16

phenytoin, during pregnancy.

Other findings sometimes seen with fetal hydantoin syndrome include developmental delays and brain malformations. Women with epilepsy who take antiepileptic drugs during pregnancy have about a 5% chance (twice the risk of the general population) of having children with malformations. Phenytoin is also known to be associated with horizontal nystagmus on lateral gaze at therapeutic levels.

Question 17

The other answer choices would have affected the fetus in different ways. Fetal alcohol syndrome is characterized by specific craniofacial, skeletal, and neurobehavioral symptoms. Lithium is linked to Ebstein anomaly of the heart in which the leaflets of the tricuspid valve are displaced toward the apex of the right ventricle, leading to “atrialization” of the right ventricle. Retinoic acid leads to high rates of spontaneous abortion, as well as major defects including?

Answer 17

micrognathia, cleft palate, thymic defects, and central nervous system malformations. Methimazole use during pregnancy is associated with aplasia cutis congenita, a disorder in which there is an absence of skin in infants.

Question 18

The use of phenytoin during pregnancy is associated with fetal hydantoin syndrome. The characteristic features include?

Answer 18

small body size, microcephaly, low nasal bridge, cleft lip, hypoplasia of distal phalanges, nail hypoplasia, and hirsutism.

Question 19

This patient presents with weight loss, heart palpitations, jitteriness, and sweating. Her mother recently had a thyroidectomy after having similar symptoms. In addition, the patient reports a “pulling” sensation in her groin, and a nontender 9-cm mass is found on pelvic examination. Her thyroid-stimulating hormone level is 0.3 µU/mL (normal range, 0.5–5.0 µU/mL), her thyroxine level is 22 µg/dL (normal range, 5–12 µg/dL), and her thyroid is found to be normal on palpitation.
The pelvic mass and the concurrent symptoms of hyperthyroidism are consistent with ?

Answer 19

struma ovarii, a thyroid hormone–secreting ovarian teratoma. The benign findings from the thyroid examination make this unlikely to be a thyroid disease, and other ovarian neoplasms are unlikely to cause overt thyroid symptoms. These tumors manifest as unilateral, cystic, pelvic masses with concomitant hyperthyroid symptoms. A biopsy specimen of the pelvic mass will reveal thyroid-type tissue containing follicles that produce thyroid hormone, as seen in the histologic sample in the image.

Question 20

No serum ß-human chorionic gonadotropin is detected in this patient, ruling out an ectopic pregnancy. Furthermore, an ectopic pregnancy would not present with signs of hyperthyroidism. Although Graves disease may account for most of the patient’s symptoms of hyperthyroidism, it does not commonly manifest with ovarian masses; ocular involvement is more common. Hashimoto thyroiditis is a cause of hypothyroidism, but this patient presents with signs of ?

Answer 20

hyperthyroidism. A serous cystadenoma would manifest with an adnexal mass and would be unlikely to cause hyperthyroidism.

Question 21

Struma ovarii is an ovarian tumor that consists of thyroid tissue. It is a cystic ovarian mass that may present with?

Answer 21

signs of excessive thyroid hormone (tachycardia, weight loss, heat intolerance) and mass effect in the pelvis.

Question 22

A 28-year-old HIV-positive woman presents for prenatal care. She states that she is 17 weeks’ pregnant, according to the date of her last menstrual period. She has not yet had any prenatal care. She is otherwise in good health.
Which of the following drugs reduces the risk of transmission of HIV to the newborn?

Answer 22

Zidovudine is a nucleoside analog that inhibits HIV reverse transcriptase, preventing the incorporation of the viral genome into host DNA. A 1994 randomized, double-blind, placebo-controlled trial involving HIV-infected women at 14-34 weeks’ gestation who had CD4+ counts >200/mm3, had no or minimal symptoms, and had not received antiretroviral treatment during their pregnancy demonstrated that of the 425 mothers who completed the trial, the treatment group had their vertical HIV transmission rate reduced by 70%.

Question 23

Efavirenz is a non-nucleoside HIV reverse transcriptase inhibitor that prevents the incorporation of the viral genome into host DNA. It has not been shown to decrease vertical transmission rates and in fact is generally not given to pregnant women because of its serious side effect profile. Efavirenz is never used alone (it can be given as part of HAART) and is usually given as part of a chronic treatment rather than as prophylaxis.
Indinavir is a viral protease inhibitor that inhibits?

Answer 23

the assembly of new virus particles.
Marviroc is an entry inhibitor that is a CCR5 receptor antagonist. This prevents the HIV virus from entering host cells.

Zidovudine is a nucleoside analog that inhibits HIV reverse transcriptase, preventing the incorporation of the viral genome into host DNA. It is frequently used for general prophylaxis and during pregnancy to reduce the risk of fetal transmission of HIV.

Question 24

The patient presents with sudden vaginal bleeding and painful abdominal cramps at 32 weeks’ gestation without trauma. She has low blood pressure and rapid heart rate indicating a bleed. The fetus is in distress within a hypertonic uterus. The patient’s history of smoking and cocaine use also point to a diagnosis of abruptio placentae, or placental abruption.
Placental abruption is the partial or complete premature separation of placenta from the uterine wall. Risk factors include smoking and cocaine use as seen in this patient, as well as trauma, hypertension, and preeclampsia. Patients present with sudden painful bleeding in the third trimester, as seen in the vignette. Complications are life threatening and include ?

Answer 24

DIC from tissue factor entering maternal circulation, maternal shock, and fetal distress or death.

Question 25

Postpartum hemorrhage and Sheehan syndrome are associated with placenta accreta/increta/percreta, where the maternal portion of the placenta, the desidua basalis, has abnormal attachment and separation after delivery. This condition would be visible on ultrasound, unlike what is seen in this patient. Preeclampsia is?

Answer 25

a condition of new-onset hypertension with either proteinuria or end-organ dysfunction after the 20th week of gestation. Abruptio placentae can be a complication of preeclampsia, but not a cause. This patient’s condition also does not include infertility as a complication.

Question 26

Bleeding in the third trimester that is bright or dark red and associated with painful abdominal cramps suggests placental abruption. Placental abruption is the partial or complete premature separation of?

Answer 26

placenta form the uterine wall. Risk factors include smoking, cocaine use, trauma, hypertension, and preeclampsia. Complications include DIC, maternal shock, and fetal distress.

Question 27

This patient’s niece has a genetic disease that causes respiratory infections and pancreatic failure, which describes ?

Answer 27

cystic fibrosis. The patient wants to assess her chances of having a child with the disease. Cystic fibrosis is caused by a mutation in the CFTR gene. Polymerase chain reaction (PCR) and sequencing can be used to determine if this woman and/or her husband is a carrier of the cystic fibrosis gene. It’s the most common single gene mutation in the white population.

Question 28

PCR is used to amplify the region of interest (see image below). First, DNA is denatured at 95 degrees Celsius to separate the DNA strands. In the next step, a primer (a short sequence of DNA) is added to the mixture and anneals to?

Answer 28

its complementary sequence on the patient’s DNA strand. The annealing process is carried out at about 55°C. Finally, nucleotide triphosphates are added and heat stable polymerase replicates the DNA sequence following each primer at 72°C.

Question 29

Through DNA amplification, PCR increases the amount of DNA encoding a specific gene of interest. Following amplification, this DNA can be sequenced. Comparison of the patient’s DNA sequence to the normal sequence and known mutations can determine?

Answer 29

If the cystic fibrosis mutation is present.

Enzyme-linked immunosorbent assay (ELISA) involves the use of antibodies to identify the presence of a particular antigen or antibody.
Gel electrophoresis involves use of an electric field to separate molecules by size, but would not be able to detect DNA mutations.
Northern blot is a test to identify specific fragments of RNA and gives information about gene transcription.

Question 30

A Southwestern blot involves a biochemical technique to identify specific DNA-binding proteins, but would not be helpful in DNA identification.
A karyotype analysis is helpful in identifying many genetic diseases caused by?

Answer 30

large chromosomal abnormalities, but a change in a few nucleotides (as is the case with CF) would not be detected.

A helpful mnemonic for the blot studies is SNoW DRoP for Southern = DNA. Northern = RNA. Western = Protein.

Question 31

Polymerase chain reaction is a method in which a small quantity of DNA is amplified using primers that are complementary to the segment of interest. After amplifying DNA, sequencing can be performed to?

Answer 31

evaluate for genetic mutations.