@marimphil wrote:
<1>A 72-year-old male is noted as having a 9-pound weight loss over the past
few weeks. His past medical history is significant for oat cell carcinoma of
the lung, without known metastases, for which he is currently undergoing
treatment. The patient states that even though his wife is preparing his
Answer
<2>A 45-year-old homeless man has a chronic cough, a cavitary lesion of the
lung, and is sputum positive for acid-fast bacilli. Which of the following
is the principle form of defense by which the patient's body fights this
infection?
Answer
<3>A researcher is examining the distribution of an ion channel protein in
the kidney. She incubates slices of kidney tissue in a dilute solution of
a specific antibody directed against the protein, then uses the
immunoperoxidase method to localize the ion channel proteins.
She notes the presence of brown pigment in a population of epithelial
Answer
<4>A 38-year-old pregnant woman with a past medical history significant for
chronic hypertension presents with a blood pressure of 158/105 mm Hg. Which
of the following antihypertensive agents would be most suitable for initial therapy in this patient?
Answer
<5>A 3 year-old boy is brought to a physician because the mother notices tha
t the child is engaging in less active play and tires easily. During physical
examination, the pediatrician notices that the child's thighs are larger
than normal for age and that the child cannot stand up without using his
arms to help. Further studies demonstrate a defective dystrophin gene in
the boy. Which of the following people in the child's family is most
likely to also have this disease?
Answer
<6> The leukocyte pictured above stains intensely with acidic dyes such
as eosin. Which of the following substances is contained in the crystalline
core of the granule at the arrow?
Answer
<7>A 7-year-old boy is brought to a physician because of a nearly confluent,
fine, erythematous, macular rash that is most pronounced on his trunk. He
has had a mild fever for 36 hours, but does not appear very sick, and is
happily playing when the pediatrician enters the examining room. Physical
examination demonstrates a reddened throat with tonsillar exudates,
enlarged cervical nodes including the occipital node, and questionable
Answer
<8>A child who has had abnormal development of the membranous bones has a
broad skull with associated facial and dental anomalies. Which other bones
are most likely to also be affected?
Answer
<9>A 33-year-old woman presents with fever, vomiting, severe irritative
voiding symptoms, and pronounced costovertebral angle tenderness.
Laboratory evaluation reveals leukocytosis with a left shift; blood
cultures indicate bacteremia. Urinalysis shows pyuria, mild hematuria,
Answer
<10>A surgical pathology specimen from a 24-year-old woman seen at a
reproductive medicine clinic demonstrates a ciliated columnar epithelium.
From which of the following locations in the female genital tract was the
biopsy obtained?
Answer
<11>In a genotypic male, the testes fail to develop, and do not secrete
testosterone or Müllerian regression factor. Which of the following
best
describes the in utero reproductive system development of this individual ?
Answer
<12>A pulmonologist is testing a patient's lung volumes and capacities using
simple spirometry. Which of the following lung volumes or capacities cannot
be measured directly using this technique?
Answer
<13>Contraction of which of the following muscles contributes most to the
backward movement of the lower jaw during the process of mastication?
Answer
<14>A 28-year-old female presents to the doctor complaining of syncopal
episodes that last a few minutes. She is not taking any medications and
has no previous medical history. EEG and EKG studies are performed and
are unremarkable. An echocardiogram shows a single ball-shaped mass
dangling in the left atrium near the mitral valve. The most likely
Answer
<15>A patient who has been exhibiting various endocrine abnormalities
has an MRI scan of the head. This scan reveals a small tumor of the
pituitary gland. If this tumor expands laterally, which of the following
nerves will most likely be affected first?
Answer
<16>A liver biopsy from a 54-year-old man shows many Mallory bodies. This
finding is most suggestive of which of the following diseases?
Answer
<17>A 27-year-old man has been arrested by the police for hitting, cursing
at, and verbally berating his wife of 8 years. The wife tells the police he
also regularly physically whips his 7-year-old son with a leather belt and
often strikes the boy with his hand. When asked why he does this, he
responds that this is "how my father treated me, it's how men should
act." This represents which of the following types of learning?
Answer
<18>A 64-year-old man presents to his doctor with aching, burning pain afte
r meals. He had been self-medicating for several months with antacids, but
he found this to be increasingly ineffective. His physician decides to take
him off the antacids and instead places him on a combination of ranitidine
and sucralfate. Why is this combination a bad idea?
Answer
<19>A 42-year-old female presents with a recent onset of fatigue, malaise,
constipation, and a 12-pound weight gain. On examination, her thyroid is
firm and enlarged. What laboratory test is most likely to confirm the
expected diagnosis?
Answer
<20>A 70-year-old man with a history of atrial fibrillation is started on an
oral anticoagulant. His prothrombin time is monitored on a regular basis. A
few months into his therapy, he begins treatment for a duodenal ulcer and
he develops symptoms of a bleeding diathesis. Which of the following ulcer
Answer
<21>An elderly woman with a history of multiple oral ulcers presents with
flaccid bullae on her scalp, face, and trunk. Manual pressure on the skin
produces separation of the upper layer of the epidermis, followed by
eventual sloughing of the skin. The patient has been in relatively good
health until recently, and denies taking any medications. A biopsy of one
Answer
<22>A 35-year-old woman notices a change in the appearance of a mole on her
neck. Physical examination reveals that the lesion is an irregular, nodular,
superficial mass with a variegated appearance. Biopsy demonstrates a
primary malignant tumor. Which of the following factors is most
predictive of the patient's long term prognosis?
Answer
<23>During embryological development, hematopoiesis occurs in different
organs at different times. Which of the following are the correct organs,
in the correct sequence, at which hematopoiesis occurs embryologically?
Answer
<24>A 6-month-old boy is brought to the pediatrician by his parents, who are
first cousins. This is their first child. Physical examination reveals a
small, thin, lethargic infant with slightly misshapen long bones. His
features are somewhat coarse. Joint movements are restricted, his corneas
are clouded, and his gums are underdeveloped. His liver is not enlarged.
Answer
<25>A particular association determines membership on the basis of members'
IQ scores. Only those persons who have documented IQ scores at least 2
standard deviations above the mean on the Wechsler Adult Intelligence
Scale (WAIS) are eligible for admission. Of a group of 200 people randomly
selected from the population at large, how many would be eligible for
Answer
<26>5 mL of synovial fluid is aspirated from an inflamed knee joint. The
fluid is yellow-white and cloudy and contains
200,000 WBC/mm3 (85% neutrophils). Needle-shaped,
strongly negatively birefringent crystals are seen both within
Answer
<27>A patient has a painful ulcer on the tip of his tongue. Which of the
following cranial nerves carries the pain sensation he experiences?
Answer
<28>A 30-year-old veterinarian on a cattle ranch presents with a 1-to-2-month
history of malaise, chills, drenching malodorous sweats, fatigue, and
weakness. He has anorexia and has lost 15 pounds. He has intermittent
fevers that range up to 103 F (39.4 C). He complains of visual blurring.
A physical examination reveals mild lymphadenopathy, petechiae, and a
Answer
<29>The parents of a 6-month-old child who was normal at birth bring her
into the clinic. Since their emigration to the U.S. from Eastern Europe
soon after her birth, the child has developed diminished responsiveness
, progressive blindness and deafness, and recently, seizures. Serum levels
of which of the following compounds would be expected to be decreased in
Answer
<30>A 60-year-old male with angina comes to the emergency room with severe
chest pain unresponsive to sublingual nitroglycerin. An EKG shows ST
segment elevation in the anterolateral leads, and thrombolytic therapy
is initiated. If streptokinase is given to this patient, it may produce
thrombolysis after binding to which of the following proteins?
Answer
<31>The left adrenal vein drains directly into which of the following veins?
Answer
<32>A premature infant develops progressive difficulty breathing over the
first few days of life. Deficient surfactant synthesis by which of the
following cell types may have contributed to the baby's respiratory problems?
Answer
<33>A surgeon performs an exploratory laparotomy, producing a large incision
in the patient's abdomen. Poor blood supply to which of the following is
most likely to cause problems during the healing process?
Answer
<34>A 1-year-old child develops voluminous watery diarrhea and vomiting. She
is brought to the pediatrician by her parents and evaluated, then sent home
with instructions for the parents to give the child an electrolyte
replacement solution. Which of the following viruses is the most likely
cause of the child's diarrhea?
<35>A 2-year-old child presents to the pediatrician with hematuria.
Examination reveals hypertension and an abdominal mass. A tumor is localized
to the right kidney and biopsy reveals a stroma containing smooth and
striated muscle, bone, cartilage, and fat, with areas of necrosis.
The gene for this disorder has been localized to which of the following
chromosomes?
Answer
<36>A newborn baby has a prominent defect at the base of his spine through
which his meninges and spinal cord protrude. A failure of which of the
following processes is the most common cause of this type of defect?
Answer
<37>A 45-year-old male presents to the physician with muscle cramps,
perioral numbness, and irritability over the past 3 to 4 months. Lab
results reveal hypocalcemia, normal albumin level, and hyperphosphatemia
. Parathyroid hormone level is decreased. Alkaline phosphatase level is
normal. Which of the following is most likely causing this clinical
Answer
<38>In which of the following organs are fenestrated endothelial cells
common?
Answer
<39>A macroscopic hepatic change known as nutmeg liver is indicative of
Answer
<40>A 26-year-old man is admitted through the emergency department to the
hospital for a heroin overdose. His heart rate is 45 beats/min, and his
blood pressure is 75/40 mm Hg. Which of the following best depicts the
results from an arterial blood sample ?
Answer
<41> The maximum expiratory flow-volume curve shown above is created when
the patient inhales as much air as possible and then expires with maximum
effort until no more air can be expired. What is the forced vital capacity
of this patient?
Answer
<42>A 25-year-old male gets into a brawl outside a bar. During the
altercation, someone pulls out a gun and shoots him in the head.
The bullet enters the man's temple and severs his right optic nerve
completely. He is quickly transported to a nearby emergency room and
an emergency physician tests his pupillary response by shining a light
Answer
<43>A patient complaining of chest pain with exercise is evaluated by
cardiac catheterization. The left anterior descending (LAD) branch of
the coronary artery is visualized but the contrast angiography is poor
. A Doppler-tipped catheter is inserted and the blood velocity is observed
to increase transiently from 10 cm/sec to 70 cm/sec and then decrease bac
k to 10 cm/sec as the probe passes a particular location in the artery
. What was the cause of these changes in velocity measurements?
Answer
<44>Type of blood vessel Fall in blood pressure (mm Hg) (% of total peripheral resistance)
Aorta and large arteries <1
Small arteries 10-20
Arterioles 50
Capillaries 25
Venules and small veins 9
Vena cave <1
The table above shows the fall in blood pressure that occurs for the
various types of blood vessels as blood flows from the aorta (100 mm Hg)
to the right atrium (0 mm Hg). Which of the following types of blood
vessel is likely to have the highest ratio of wall cross-sectional
Answer
<45>Evaluation of an infant with a variety of congenital abnormalities
reveals hypocalcemia due to a lack of parathyroid hormone. On x-ray, the
thymic shadow is absent. A failure of development and differentiation of
which of the following embryonic structures would most likely be
Answer
<46>A person lifts one foot prior to taking a step. Which of the following
nerves innervates the muscle group that allows the person to maintain
balance by holding the weight of his body over the foot remaining on
the ground?
Answer
<47>A 21-year-old college student from Connecticut with a past history
of Lyme disease presents with chronic pain and swelling in his right
knee. He states that he has had problems with the knee for the past
two years. Which of the following HLA alleles would you expect to
Answer
<48>Which of the following metabolic processes occurs exclusively in
the mitochondria?
Answer
49>An alert pediatric intern notices that a neonate with dysmorphic facies
is twitching abnormally. As he watches, the baby experiences a seizure.
Stat laboratories indicate a glucose of 90, serum sodium of 140, serum
potassium of 4.2 and serum calcium of 3.9. Over the next several months,
Answer
50>A 2-month-old boy is evaluated for failure to thrive. As the pediatrician
is examining the patient, she witnesses a seizure. Physical examination
is remarkable for hepatomegaly, a finding later confirmed by CT scan,
which also reveals renomegaly. Serum chemistries demonstrate severe
hypoglycemia, hyperlipidemia, lactic acidosis, and ketosis. Which of
Answer
Answer
Answers
1>The correct answer is B. One of the most common side effects of any
antineoplastic therapy is weight loss secondary to decreased appetite
and/or nausea and vomiting. Furthermore, weight loss due to decreased
food intake tends to occur more frequently in elderly patients receiving
antineoplastic therapy. One medication that has consistently helped to
increase appetite in such patients is megestrol acetate. This agent is a
progestational hormone with antineoplastic properties used in the
treatment of advanced carcinoma of the breast and endometrium.
Megestrol, when given in relatively high doses, can substantially
increase the appetite in most individuals, even those with advanced
cancer.
Amitriptyline (choice A) is a tricyclic antidepressant used in the
treatment of depression. There is nothing mentioned in the case study to
suggest that the patient is clinically depressed; hence, this agent
would provide no benefit.
Methotrexate (choice C) is an antimetabolite and folic acid antagonist
commonly used in various neoplastic disorders and in the treatment of
rheumatoid arthritis. Since nausea, vomiting, and ulcerative stomatitis
are common side effects of this medication, its usage in this patient
would not be recommended.
Neostigmine (choice D) is a carbamylating acetylcholinesterase inhibitor that would not increase appetite.
Prochlorperazine (choice E) is a phenothiazine derivative used primarily
to control severe nausea and vomiting. This patient is not experiencing
nausea. Furthermore, this agent does not possess appetite-stimulating
properties.
2>The correct answer is B. The principle host defense in
mycobacterial infections (such as this patient's tuberculosis) is
cell-mediated immunity, which causes formation of granulomas.
Unfortunately, in tuberculosis and in many other infectious diseases
characterized by granuloma formation, the organisms may persist
intracellularly for years in the granulomas, only to be a source of
activation of the infection up to decades later.
While antibody-mediated phagocytosis (choice A) is a major host defense
against many bacteria, it is not the principle defense against
Mycobacteria.
IgA-mediated hypersensitivity (choice C) is not involved in the body's defense against Mycobacteria.
IgE-mediated hypersensitivity (choice D) is not involved in the body's
defense against Mycobacteria. It is important in allergic reactions.
Neutrophil ingestion of bacteria (choice E) is a major host defense
against bacteria, but is not the principle defense against Mycobacteria.
3>The correct answer is E. The immunoperoxidase method uses
horseradish peroxidase to produce a visible pigment when a specific
antibody binds to antigenic sites in the tissue. Binding of the antibody
to the epithelial cells indicates that the protein in question is being
expressed by those cells. The positive immunoperoxidase results
obtained here suggests that the channel protein is expressed in proximal
convoluted tubular epithelium, since this is the only site in the
kidney at which the epithelial cells have a "brush border." The brush
border is made of microvilli, which enhance the proximal tubules'
ability to reabsorb plasma constituents filtered at the glomeruli.
4>The correct answer is D. Pregnant women with chronic hypertension
"require" antihypertensive therapy when the diastolic pressure is
greater than 100 mm Hg; however, some clinicians may decide to treat
patients with diastolic blood pressures less than 100 mm Hg. For the
initiation of therapy, methyldopa is still considered to be the agent of
choice. Methyldopa is converted intraneuronally to
a-methylnorepinephrine, an alpha-2 adrenergic agonist, which is
subsequently released. Release of a-methylnorepinephrine in the medulla
leads to a decrease in sympathetic outflow, thus lowering blood
pressure. Methyldopa has been safely used in the treatment of
hypertension during pregnancy; this agent is not associated with the
development of teratogenic or other fetal abnormalities.
Diuretics, such as bumetanide (choice A) and hydrochlorothiazide (choice
C), are often avoided since these agents can produce hypovolemia,
leading to reduced uterine blood flow. Although these agents can be used
during pregnancy, methyldopa and hydralazine are the drugs of choice
for hypertension during pregnancy.
Fosinopril (choice B) is an angiotensin-converting enzyme (ACE)
inhibitor that should not be administered to pregnant women, especially
in the second or third trimesters. These agents have been associated
with severe fetal and neonatal injury, such as hypotension, neonatal
skull hypoplasia, anuria, renal failure, and death.
Along the same lines, the use of the angiotensin II receptor
antagonists, such as valsartan (choice E), is not recommended since
these agents cause fetal complications similar to the ACE inhibitors.
5>The correct answer is D. The disease is Duchenne muscular
dystrophy, an X-linked recessive muscular disease usually caused by a
deletion involving the dystrophin gene. This defect produces accelerated
muscle breakdown leading initially to proximal muscle weakness, then
later to generalized weakness that typically begins before age 5. A
feature of X-linked recessive diseases is that carrier mothers pass the
disease to half their sons; affected fathers can have carrier daughters
but not affected sons. Since the mother is presumably normal (because
the disease is X-linked), she must be a carrier to have an affected son,
and the grandmother must also be a carrier, therefore the mother's
brother (maternal uncle) may also have the disease.
The father's (choice A) side of the family, including the father's
brother (choice B), most likely does not carry the defective gene (since
they themselves would be affected, and furthermore since the father
cannot pass the gene on to a son). It would be extremely unlikely for a
carrier female to marry an affected male (and the question does not
mention any similar symptoms in the father).
The mother (choice C) and possibly the sister (choice E) are carriers of, but not affected by, the defective gene.
6>The correct answer is B. The cell pictured is an eosinophil, a
member of the granulocytic lineage of white blood cells. The crystalline
core of the granule contains a protein called the major basic protein,
which appears to function in the destruction of parasites. Major basic
protein also has deleterious effects on epithelial cells in patients
with asthmatic reactions. The light component around the dense
crystalline core contains products such as histaminase, arylsulfatase,
and other enzymes.
Lactoferrin (choice A) is found in the specific granules of the
neutrophil. It inhibits the growth of bacteria by interfering with iron
metabolism.
Myeloperoxidase (choice C) is found in the azurophilic (large) granule
of the neutrophil. This enzyme is also destructive to bacteria,
destroying their cell walls.
Histamine (choice D) is produced by the basophil and the mast cell. The
histaminase of the eosinophil regulates the inflammatory reaction of
these two cell types.
Tartrate-resistant acid phosphatase (choice E) is a marker for hairy cell leukemia, a neoplasm of the B lymphocyte line.
7>The correct answer is E. This presentation (fine, nonblotchy,
truncal rash in a not-very-ill child) is characteristic of rubella, or
German measles. IgM specific for rubella can often be detected in serum
within 1-2 days of developing the rash. The principal significance of
this disease is that it can cause a devastating congenital infection
characterized by ocular problems (cataracts, retinopathy,
microphthalmos, glaucoma), cardiovascular problems (patent ductus
arteriosus, ventricular septal defect, pulmonary stenosis), deafness,
thrombocytopenic purpura, hepatosplenomegaly, CNS problems, and bony
lesions.
Bullous pemphigoid (choice A) produces large, tense blisters.
Dermatitis herpetiformis (choice B) causes recurrent crops of small vesicles or papules.
Herpes simplex (choice C) is characterized by crops of vesicles on oral or genital sites.
Measles (choice D) causes a blotchy, maculopapular erythematous rash
that begins on the face and spreads downward. Patients with measles are
usually much sicker than those with German measles, and Koplik spots
maybe seen on the buccal mucosa.
8>The correct answer is A. In a syndrome called cleidocranial
dysostosis, absence of part of the clavicles accompanies a broad skull,
and facial and dental anomalies. Note that you could also have answered
this question by noting that of the bones listed, only the clavicles
form by intramembranous ossification.
The femurs (choice B), metatarsals (choice C), phalanges (choice D), and
tibias (choice E) are cartilaginous (formed by endochondral
ossification) rather than membranous bones.
9>The correct answer is A. Acute pyelonephritis is an infectious
disease involving the kidney parenchyma and the renal pelvis.
Gram-negative bacteria, such as Escherichia coli, Proteus, Klebsiella,
and Enterobacter, are the most common causative organisms in acute
pyelonephritis. Laboratory evaluation will often reveal leukocytosis
with a left shift, and urinalysis typically shows pyuria, varying
degrees of hematuria, and white cell casts. Since bacteremia is present,
the patient should be hospitalized and empirically started on IV
ampicillin and gentamicin. This regimen may be need to be changed,
however, once the sensitivity results are available.
Erythromycin (choice B) and tetracycline (choice E) are both
bacteriostatic antibiotics and would not be recommended in a patient
with a severe infection, such as acute pyelonephritis with bacteremia.
Vancomycin (choice C) is primarily used in the treatment of severe gram-positive infections.
Phenazopyridine (choice D) is a urinary analgesic, and nitrofurantoin
(choice D) is a urinary tract anti-infective. Although nitrofurantoin is
indicated for the treatment of "mild" cases of pyelonephritis, as well
as cystitis, this patient's condition is severe and should be treated
with appropriate antibiotics.
10>The correct answer is C. The fallopian tube is the only structure
in the female genital tract with a ciliated columnar epithelium; the
beating of the cilia helps move the egg into the uterus. This fact is
also sometimes clinically helpful since dilated and deformed fallopian
tubes can be microscopically distinguished from cystic ovarian tumors by
the presence of the cilia.
The cervix (choice A) and vagina (choice E) are lined by squamous epithelium.
The endometrium (choice B) is lined by columnar epithelium (although a few ciliated cells may be present).
The covering of the ovary (choice D) is cuboidal epithelium, and cysts
within the ovary can be lined by cuboidal or non-ciliated columnar
epithelium.
11>The correct answer is B. The description is that of gonadal
dysgenesis. In the absence of testosterone, the Wolffian ducts will
regress and fail to differentiate into normal male internal reproductive
tracts. In the absence of Müllerian regression factor, the Müllerian
ducts will automatically differentiate into oviducts and a uterus.
Differentiation of the male external genitals is dependent on adequate
dihydrotestosterone (via an action of 5 a-reductase on testosterone). In
the absence of testosterone, female-type external genitalia will
develop.
Selective dysgenesis of the Sertoli cells could produce the situation
described in choice A. Normal Leydig cells would secrete testosterone
and produce normal male-type internal and external tracts. However, the
absence of Müllerian regression factor, which is secreted by the Sertoli
cells, would allow formation of female-type internal structures as
well.
Female-type internal reproductive tract and male-type external genitalia
(choice C) would not be likely to occur under any circumstances.
The situation described in choice D could occur with 5 a-reductase
deficiency. Normal male-type internal tracts can form because there is
no requirement for dihydrotestosterone. Müllerian regression factor will
prevent differentiation of female-type internal tracts. Since
differentiation of the normal male external genitals requires
dihydrotestosterone, 5 a-reductase deficiency will lead to feminization.
The situation described in choice E is normal, and would not occur in the individual described who has testicular dysgenesis.
12>The correct answer is B. The functional residual capacity is the
amount of air left in the lungs after a normal expiration. Because this
volume cannot be expired in its entirety, it cannot be measured by
spirometry. Essentially, lung volume that contains the residual volume,
which is the amount of air remaining after maximal expiration (e.g.,
functional residual capacity and total lung capacity), cannot be
measured by spirometry. These volumes can be determined using helium
dilution techniques coupled with spirometry or body plethysmography.
The expiratory reserve volume (choice A) is the volume of air that can be expired after expiration of a tidal volume.
The inspiratory reserve volume (choice C) is the volume of air that can be inspired after inspiration of a tidal volume.
Tidal volume (choice D) is the amount of air inspired or expired with each normal breath.
Vital capacity (choice E) is the volume of air expired after a maximal inspiration
13>The correct answer is E. Mastication is a complex process
involving alternating elevation, depression, forward movement, and
backward movement of the lower jaw. The backward movement step is
accomplished by the posterior fibers of the temporalis muscle.
The digastric (choice A) helps to depress the lower jaw during chewing.
The lateral pterygoid (choice B) helps to move the lower jaw forward during chewing.
The medial pterygoid (choice C) helps to elevate the lower jaw during chewing.
The mylohyoid (choice D) helps to depress the lower jaw during chewing.
14>The correct answer is C. The vignette illustrates a typical
presentation for a tumor of the heart. Primary cardiac tumors are rare
and usually require an intensive work-up to pinpoint the diagnosis. 75%
of primary cardiac tumors are benign and among these, myxoma is the most
common. The tumors are usually single; the most common location is the
left atrium. They may cause syncopal episodes or even shock and death
due to obstruction by a "ball valve" mechanism.
Angiosarcoma (choice A) is a malignant tumor of vascular origin that can
occur as a primary cardiac tumor. It is the most common malignant
primary cardiac tumor, but it is still very rare. Angiosarcoma usually
affects the right side of the heart.
Mesothelioma (choice B) is a benign tumor of mesothelial origin that can
rarely present as a primary cardiac tumor. It is usually a small
intramyocardial tumor that presents with disturbances of the conduction
system of the heart.
Rhabdomyoma (choice D) is a benign tumor of muscle origin. It can occur
as a primary cardiac tumor, typically in infants and children, in whom
it may be associated with tuberous sclerosis. It usually occurs in the
ventricles.
Rhabdomyosarcoma (choice E) is a malignant neoplasm that can also occur
as a rare primary cardiac tumor. It is of muscle origin and usually
affects the right heart.
15>The correct answer is A. The pituitary gland is located in the
pituitary fossa within the skull. The floor of this fossa is formed by
the sella turcica. The lateral walls of the fossa are formed by the
cavernous sinuses. The abducens nerve passes through the cavernous sinus
along with the internal carotid artery. As the tumor expands laterally,
the first nerve that will be encountered is the abducens nerve,
producing a lateral rectus palsy.
The oculomotor nerve (choice B) lies in the lateral wall of the
cavernous sinus. It is further from the pituitary gland than is the
abducens nerve.
The optic nerve (choice C) is anterosuperior to the pituitary gland.
Upward expansion of the tumor may compress the optic chiasm.
The trigeminal nerve (choice D) is found posterior to the cavernous
sinus. Two of its three divisions (ophthalmic and maxillary divisions)
pass through the lateral wall of the cavernous sinus and are further
from the pituitary gland than is the abducens nerve.
The trochlear nerve (choice E) is also in the lateral wall of the
cavernous sinus, and would be affected later if the tumor continued to
expand.
16>The correct answer is A. Mallory bodies are eosinophilic
cytoplasmic inclusions ("alcoholic hyaline") that are found in the
largest numbers in alcoholic hepatitis. They were originally considered
to be pathognomic of alcohol abuse, but have since been found (in much
smaller numbers) in many other liver conditions.
Alpha1-antitrypsin deficiency (choice B) involvement of the liver is
characterized by periodic acid Schiff (PAS)-positive cytoplasmic
granules in hepatocytes.
Hepatitis A (choice C) and hepatitis B (choice D) infections are definitively established with serologic markers.
In Wilson's disease (choice E), there is excess copper deposition in the liver
17>The correct answer is E. In social learning, also known as
modeling, behavior is acquired by watching other persons and
assimilating their actions into the behavioral repertoire. There is no
verbal or cognitive process (choice B) that is involved, no
reinforcement (as in operant conditioning; choice D), no pairing of
stimuli to get stimulus substitution (as in classical conditioning;
choice A), nor any early-life bonding or imprinting (choice C) involved
in this type of process. Because behaviors such as spousal abuse, child
abuse, and elder abuse are all based on observing and incorporating
behaviors from significant others, the person displaying the behaviors
does not realize the behaviors are inappropriate and is typically very
resistant to change. The fact that the learning is nonverbal and not
dependent upon reinforcement contributes to the resistance to change.
18>The correct answer is B. Sucralfate is a promising drug that is
not presently in widespread use because it is incompatible with H2
antagonists such as cimetidine, ranitidine, famotidine and nizatidine.
Sucralfate is aluminum sucrose sulfate, a sulfated disaccharide, which
polymerizes and binds to ulcerated tissue. It forms a protective coating
against acid, pepsin and bile, giving the tissue a chance to heal.
Unfortunately, a low gastric pH is required for polymerization, meaning
that sucralfate is incompatible with drugs that reduce gastric acidity,
such as H2 blockers and antacids. The moral of the story is that you
cannot assume that two medications that are individually helpful in a
medical condition will be synergistic. Learning the mechanisms by which
the drugs work will help you spot potential interactions and earn you
points on the USMLE.
19>The correct answer is B. The patient's presentation is consistent
with hypothyroidism. Serum thyroid-stimulating hormone (TSH) measurement
(choice B) is most likely to confirm the empiric diagnosis. TSH levels
usually rise above normal before serum thyroxine (T4; choice C) and
serum triiodothyronine (T3; choice D) levels do, even in mild cases of
hypothyroidism. Therefore, TSH measurement would be the most accurate
test to determine the presence of hypothyroidism regardless of the
severity.
A high titer of antithyroid antibodies (choice A) is characteristic of
chronic thyroiditis, which is the most common cause of hypothyroidism.
However, detection of these antibodies would not indicate if
hypothyroidism was present.
T3 resin uptake (choice E) measurement is not an accurate test of
thyroid function; it is primarily used to exclude various abnormalities
in the thyroid-hormone binding proteins.
20>The correct answer is A. Warfarin is the oral anticoagulant the
patient was most likely taking. This drug is commonly prescribed to
patients with atrial fibrillation to prevent the formation of atrial
thrombi. Warfarin increases prothrombin time (PT) because it interferes
with the synthesis of the vitamin K clotting factors of the liver (II,
VII, IX, and X) and therefore necessitates regular monitoring of the PT.
Cimetidine is an H2-blocker that inhibits hepatic enzymes, including
those that metabolize warfarin. Consequently, coadministration of
warfarin and cimetidine results in enhanced warfarin activity, producing
pronounced anticoagulation and the bleeding diathesis in the patient in
question. Cimetidine has one of the worst side effect profiles of all
the H2-blockers and may also result in gynecomastia in men.
Famotidine (choice B) is an H2-blocker that does not affect liver metabolism.
Misoprostol (choice C) is a prostaglandin E1 analog used in peptic ulcer disease. It does not affect hepatic metabolism.
Omeprazole (choice D) is a proton-pump inhibitor used to decrease acid
production in patients with peptic ulcer disease or reflux. It does not
affect drug metabolism by the liver.
Ranitidine (choice E) is another H2-blocker. It does not inhibit liver enzymes as strongly as cimetidine does.
21>The correct answer is C. Bullae with the cleavage plane above the
basal layer of the epidermis suggests pemphigus vulgaris, which is
caused by autoantibodies to intercellular junctions of epidermal cells.
The autoantibodies decrease the ability of the keratinocytes to adhere
to one another, permitting formation of vesicles and bullae. Oral
involvement is common, and often precedes the characteristic skin
lesions. Separation of the epidermis upon manual stroking of the skin is
known as Nikolsky's sign. This sign is present in other disorders such
as Stevens-Johnson syndrome, but we are told the woman is not taking any
medications, a typical cause of Stevens-Johnson syndrome in the adult
population.
Antibodies to epidermal basement membrane proteins (choice A) are seen
in bullous pemphigoid, which is a bullous disease characterized by
blisters with a cleavage line between the epidermis and dermis.
Antibodies to glycoprotein IIb/IIIa (choice B) are seen in autoimmune thrombocytopenic purpura.
Antibodies to intrinsic factor (choice D) are seen in pernicious anemia.
Antibodies to Type IV collagen (choice E) are seen in Goodpasture's syndrome.
22>The correct answer is D. The lesion is a malignant melanoma.
Melanomas can develop either de novo or in an existing mole. Sunlight
exposure is a significant risk factor and fair-skinned persons are at
increased risk of developing melanoma. The most significant factor for
long term prognosis is the depth of the lesion, since the superficial
dermis lies about 1 mm under the skin surface, and penetration to this
depth is associated with a much higher incidence of metastasis than is
seen with a more superficial location.
The circumference of the lesion (choice A) is much less important than
depth, since one form of melanoma (superficial spreading) can still have
good prognosis despite large size, if it has not extended to the depth
of the superficial dermal lymphatic bed.
The darkness (choice B) or degree of variation in color (choice C) do
not have prognostic significance once melanoma is diagnosed.
Irregularity, or fuzziness at the border (choice E) of a mole-like
lesion is a good clue to potential malignancy, but does not affect
prognosis once a melanoma is diagnosed.
23>The correct answer is E. By the third week of development,
hematopoiesis begins in the blood islands of the yolk sac. Beginning at 1
month of age and continuing until 7 months of age, blood elements are
also formed in the liver. Hematopoiesis occurs in the spleen and
lymphatic organs between 2 and 4 months, and in the bone marrow after 4
months.
24>The correct answer is E. The patient has I-cell disease, also
known as mucolipidosis II, which is due to a defective
UDP-N-acetylglucosamine-1-phosphotransferase, the enzyme that
phosphorylates mannose on enzymes destined for lysosomes. Proteins coded
by nuclear DNA are synthesized on cytoplasmic ribosomes, which may be
either "free" or associated with the endoplasmic reticulum to form the
rough endoplastic reticulum (RER). Proteins synthesized on the RER are
transferred into the Golgi apparatus, where they undergo further
modifications that determine whether they remain part of the Golgi
apparatus, become part of the plasma membrane, or are shipped to
lysosomes or mitochondria. Proteins not marked for transport to a
specific intracellular site follow the default pathway and are exported
into the extracellular compartment. The signal for transport of the acid
hydrolases (and probably other enzymes) to the lysosomes is
phosphorylation of a terminal mannose moiety on an N-linked
oligosaccharide to form mannose 6-phosphate. In I-cell disease, this
terminal mannose moiety is not phosphorylated, and the acid hydrolases
follow the default pathway and are secreted.
Deficiency of alpha-L-iduronidase results in lysosomal accumulation of
dermatan sulfate and heparan sulfate (choice A) in several conditions
such as mucopolysaccharidosis I, Hurler's disease, or Hurler's/Scheie
disease.
Hexosaminidase A deficiency (Tay-Sachs disease) is one example of a
condition in which ganglioside accumulation occurs (choice B).
There are a number of diseases in which glycogen degradation (choice C)
is defective. These are collectively termed glycogen storage diseases
since they result in abnormal cellular accumulation of glycogen. In
Pompe's disease, or type II glycogen storage disease, a lysosomal
glucosidase is deficient, resulting in lysosomal glycogen accumulation.
Deficiency of sphingomyelinase (choice D), an enzyme involved in degradation of sphingomyelin, results in Niemann-Pick disease.
Phosphorylation of tyrosine moieties (choice F) is unrelated to
lysosomes or lysosomal enzymes; however, decreased ability to
phosphorylate tyrosine moieties might be associated with diabetes or
dwarfism.
25>The correct answer is E. 95% of a normally distributed population
will fall between plus or minus 1.96 standard deviations from the mean.
Since the population is normally distributed with regard to IQ, this
means that approximately 2.5% of the population will have IQ scores 2
standard deviations or more above the mean, and 2.5% of the population
will have IQ scores 2 standard deviations or more below the mean. 2.5%
of 200 people is 5 people.
26>The correct answer is E. All the compounds listed can produce
crystals in joint fluid, but only monosodium urate (associated with
gout) and calcium pyrophosphate dihydrate (associated with CPPD crystal
deposition disease, also called pseudogout), and to lesser degree basic
calcium phosphate (apatite-associated arthropathy), have a high
likelihood of being encountered on a step 1 USMLE exam. The crystals
described are those of monosodium urate. Be careful not to answer "uric
acid" if that is listed as an alternative choice on an exam, since the
sodium salt is the predominant species in vivo.
Basic calcium phosphate (choice A) is seen in apatite-associated
arthropathy and produces spherical clumps of nonbirefringent
submicroscopic crystals.
Calcium oxalate crystals (choice B) are seen in primary oxalosis and are bipyramidal, positively birefringent crystals.
Calcium pyrophosphate dihydrate crystals (choice C) are a feature of
pseudogout and are rod-to-rhomboidal-shaped, weakly positively
birefringent crystals.
Cholesterol crystals (choice D) are seen in chronic and chylous
effusions in inflammatory and degenerative arthritis, where they form
large, flat, rhomboidal plates with notched corners.
27>The correct answer is B. The innervation of the tongue is complex.
The mandibular division of the trigeminal nerve (V3) carries general
somatic sensation from the anterior two-thirds of the tongue.
The maxillary division (V2, choice A) carries somatic sensation from the palate, upper gums, and upper lip.
The facial nerve (VII, choice C) carries taste from the anterior two-thirds of the tongue.
The glossopharyngeal nerve (IX, choice D) carries sensation and taste from the posterior one-third of the tongue.
The vagus nerve (X, choice E) carries sensation from the lower pharynx.
28>The correct answer is B. Brucella abortus produces a chronic,
granulomatous disease with caseating granulomas. Most cases occur in
four states (Texas, California, Virginia, and Florida), and are
associated with cattle, in which it produces spontaneous septic
abortions. Most cases of brucellosis produce mild disease or fevers of
unknown origin. However, Brucella spp. can infect the cardiovascular
system and cause a localized infection. B. abortus is the most common
species to cause endocarditis. The aortic valve is most commonly
involved, followed by the mitral valve, and then both valves. Most cases
of brucellosis are associated with occupational exposure, in persons
such as veterinarians, ranchers, and those who handle carcasses.
Bacillus anthracis (choice A) is the causative agent for anthrax. It
usually produces cutaneous disease (malignant pustule or eschar) at the
site of inoculation in handlers of animal skins. It can also produce a
severe hemorrhagic pneumonia (Woolsorter's disease) and septicemia.
At-risk groups include those who handle animal carcasses or skins.
Coccidioides immitis (choice C) is a dimorphic fungal disease producing a
granulomatous pulmonary syndrome that is more severe in dark-skinned
individuals. Disseminated disease occurs most often in Filipinos,
Mexicans, and Africans. The infective form is the arthrospore; the
diagnostic form in tissue is the spherule containing endospores. The
disease is endemic in the San Joaquin River Valley. At-risk groups
include military personnel, agricultural workers, construction workers,
oil field workers, archaeology students, participants in outdoor sports,
and sightseers. Remote infections from fomites (cotton harvested in the
Southwestern U.S.) have been reported.
Erysipelothrix rhusiopathiae (choice D) is a pleomorphic, gram-negative
rod that causes a localized skin infection. It is an occupational
disease of fishermen, fish handlers, butchers, meat-processing workers,
poultry workers, farmers, veterinarians, abattoir workers, and
housewives.
Trichinella spiralis (choice E) is a nematode infection caused by the
ingestion of larvae found in undercooked meat. Pork is the most common
contaminated meat. However, outbreaks in the northern parts of the U.S.
have been associated with eating undercooked infected bear meat.
Symptoms include diarrhea, periorbital edema, myositis, fever, and
eosinophilia.
29>The correct answer is B. This patient has Tay-Sachs disease, an
autosomal recessive disorder caused by the deficiency of hexosaminidase
A, which leads to the accumulation of ganglioside GM2 in neurons,
producing a degenerative neurologic disease. Children appear normal at
birth, but then begin to suffer from diminished responsiveness,
deafness, blindness, loss of neurologic function, and seizures. A
cherry-red spot on the macula may be seen by ophthalmoscopic
examination. Death usually occurs by 4 to 5 years of age. There is no
therapy. The incidence is higher among Jews of Eastern European descent.
Since the parents must be heterozygotes for the mutant hexosaminidase A
allele, they would be expected to have diminished levels of the enzyme.
A defect in the dystrophin (choice A) gene produces Duchenne muscular
dystrophy, characterized by onset of weakness in early childhood.
A severe deficiency in HGPRT (choice C) will lead to Lesch-Nyhan
syndrome, characterized by excessive uric acid production, mental
retardation, spasticity, self-mutilation, and aggressive, destructive
behavior.
Deficiency of phenylalanine hydroxylase (choice D) results in classic
phenylketonuria, a disease in which phenylalanine, phenylpyruvate,
phenylacetate, and phenyllactate accumulate in plasma and urine.
Clinically, there is a musty body odor and mental retardation.
Hypophosphatemic rickets is an X-linked dominant condition causing
abnormal regula