A 13-year-old boy is brought to the emergency room by ambulance after collapsing while playing at his school.
The teacher states that while playing tag, the boy had difficulty breathing, became tired, and fell to the ground
without losing consciousness. While trying to catch his breath, he made high-pitched inspiratory noises. On
arrival at the hospital, the boy appears lethargic and in moderate respiratory distress, with a respiratory rate of
30 per minute. Physical examination of the chest reveals decreased breath sounds in all lung fields with coarse
rhonchi and wheezes throughout. An arterial blood gas on 50% oxygen is as follows: pH = 7.34 PCO2 = 45 PO2 =
55 Bicarbonate = 14 Which of the following sets of pulmonary function test results would most likely be obtained
in this patient?
A. High FVC, high FEV-1, high TLC
B. High FVC, high FEV-1, low TLC
C. Low FVC, high FEV-1, low TLC
D. Low FVC, low FEV-1, high TLC
E. Low FVC, low FEV-1, low TLC
Explanation:
The correct answer is D. This patient is having an acute asthma attack. Asthma is an obstructive lung disease
primarily affecting air movement out of the lungs (exhalation). The airways (especially the large bronchioles) are
hypersensitive to irritating stimuli, such as allergens and smoke. Local mast cell histamine release causes
mucous secretion and smooth muscle contraction leading to bronchoconstriction. Certain allergic "triggers"
(cats, pollen, hay, etc.) can precipitate attacks. Symptoms include coughing, difficulty breathing, and wheezing.
Physical examination of the lungs often reveals wheezes and coarse lung sounds, although in severe cases one
may hear only decreased breath sounds and no wheezes due to very poor air flow. On pulmonary function tests
asthmatics show an obstructive pattern. Both the FEV-1 (maximum volume exhaled in one second) and the FVC
(maximum volume of air that can be exhaled in one breath) are decreased. The hallmark of obstructive lung
disease, however, is a decreased FEV-1/FVC ratio. The total lung capacity (TLC) is often increased in acute
asthma attacks as patients tend to hyperinflate to obtain more oxygen while being unable to exhale efficiently.
Thus, this patient has a low FEV-1, a low FVC, and a high TLC.
A patient complains of excessive thirst and urination. Laboratory tests show that serum osmolarity is 310 mOsm/L
and urine osmolarity is 90 mOsm/L. Plasma glucose is normal. Water deprivation (12 hours) fails to increase urine
osmolarity. Subsequent injection of vasopressin also fails to increase urine osmolarity. Which of the following is
the most likely diagnosis?
A. Diabetes mellitus
B. Nephrogenic diabetes insipidus
C. Neurogenic diabetes insipidus
D. Primary hyperparathyroidism
E. Primary polydipsia
Explanation:
The correct answer is B. Nephrogenic diabetes insipidus results in excessive excretion of free water in the urine
because of an inability of the kidney to respond to vasopressin (antidiuretic hormone). It can occur in
association with certain renal diseases that prevent the normal formation of the medullary concentration
gradient. In this case, the kidney is unable to produce a concentrated urine. Congenital nephrogenic diabetes
insipidus could be due to a defect in the renal V2 receptor, Gs protein, or other steps in the normal formation of
cyclic AMP. Plasma levels of vasopressin are usually increased because of the hyperosmolarity of the serum.
Water deprivation will fail to increase urine osmolarity in both neurogenic and nephrogenic diabetes insipidus.
However, subsequent injection of vasopressin will concentrate the urine in the case of neurogenic diabetes
insipidus (choice C), but not in nephrogenic diabetes insipidus. Certain drugs (e.g., lithium) can also produce
similar symptoms.
Diabetes mellitus (choice A) causes polyuria because of an osmotic diuresis due to glucosuria. This sort of
diuresis does not involve the loss of much free water and the urine osmolarity tends toward that of the plasma
(not 90 mOsm/L, as in the patient above). Furthermore, plasma glucose is normal in this patient, making
diabetes mellitus unlikely.
Some patients with primary hyperparathyroidism (choice D) complain of increased urination. This is due to an
osmotic diuresis, produced in this case by hypercalciuria. When serum levels of calcium exceed 12 mg/dL, the
kidney's ability to reabsorb filtered calcium is overwhelmed and hypercalciuria ensues.
Primary polydipsia (choice E) is a psychological disorder characterized by excessive water drinking. It too
produces polyuria, but the excretion of free water is appropriate. These patients typically present with
decreased serum osmolarity (due to the dilutional effect of the ingested water). Furthermore, water deprivation
should produce a concentrated urine. It is helpful to remember that the water deprivation test can distinguish
between primary polydipsia and diabetes insipidus, but it cannot distinguish between neurogenic and
nephrogenic diabetes insipidus.
Q3
A patient complains of heat intolerance, fine tremors in his hands, and palpitations. Laboratory data reveal that serum
T4 is increased compared to normal. The results of a radioactive iodine uptake test (RAIU) are shown above. Which of
the following best explains these findings?
A. Graves' disease
B. Surreptitious ingestion of thyroxine to lose weight
C. Thyroid hormone receptor insensitivity
D. Toxic adenoma
E. TSH-secreting tumor in the pituitary
Explanation:
The correct answer is B. Ingestion of exogenous thyroxine (sometimes called factitious thyrotoxicosis) could explain
the patient's symptoms related to hyperthyroidism, and could explain the increase in serum T4. The decrease in
radioactive iodine uptake is due to decreased serum TSH resulting from the negative feedback effects of the excess
T4. Note that hyperthyroidism is not always associated with increased radioactive iodine uptake.
Both Graves' disease (choice A), which is characterized by increased production of thyroid-stimulating
immunoglobulins, and a TSH-secreting tumor in the pituitary (choice D), would produce signs and symptoms of
hyperthyroidism, but would be associated with increased radioactive iodine uptake. Overactivation of the TSH
receptor in the thyroid gland in both cases would increase the iodine trapping mechanism in the follicle cells.
Thyroid hormone receptor insensitivity (choice C) would produce signs and symptoms consistent with hypothyroidism
(cold intolerance, lethargy, bradycardia, etc.). Furthermore, the negative feedback effects of thyroid hormone in the
hypothalamus and pituitary would be diminished (since this is also a receptor-mediated event) and serum levels of
TSH would be increased, producing an increase in radioactive iodine uptake. Note that hypothyroidism is not always
associated with decreased radioactive iodine uptake.
With toxic adenoma (choice E), the thyroid gland autonomously secretes excessive thyroid hormone; increased
iodine uptake would be needed to support this overproduction. The increased serum levels of thyroid hormone
inhibit TSH secretion from the anterior pituitary and the thyroid tissue undergoes atrophy.
A 15-year-old white male presents with a hemarthrosis of the right knee joint and a recent history of protracted
bleeding from cuts or scrapes. He has no family history of bleeding disorders. The patient also notes a long
history of chronic abdominal discomfort and diarrhea, which has been worse for the last 6 months, occasionally
accompanied by fever. Physical examination reveals a patient at the 5th percentile for both height and weight; an
actively bleeding rectal fissure is also noted. Both prothrombin time and the partial thromboplastin time are
prolonged. Laboratory evaluation of the blood is likely to reveal low levels of
A. factor VIII
B. factor IX
C. factors II, VII, IX, and X
D. factors II, V, VII, IX, and X
E. von Willebrand's factor
Explanation:
The correct answer is C. Low levels of factors II, VII, IX, and X are seen in vitamin K deficiency, leading to
prolonged prothrombin time (PT) and partial thromboplastin time (APTT). Vitamin K deficiency is occasionally
severe enough in obstructive jaundice, pancreatic disease, or small bowel disease to cause a bleeding
diathesis. This patient has evidence of small bowel disease and a history that is suggestive of Crohn's disease
(chronic abdominal discomfort, diarrhea and fever). Crohn's disease is also characterized by rectal fissures,
growth retardation and malabsorption. Crohn's disease causes malabsorption of fat-soluble vitamins (A,D,E,K)
by several mechanisms. It most often involves the terminal ileum, which is responsible for the recycling of bile
acids necessary for the transport and proper absorption of lipids. Small intestinal Crohn's disease itself can
cause malabsorption by reducing the surface area available for absorption of nutrients. Finally, Crohn's
disease can cause the development of fistulae, which can lead to exclusion of loops of bowel, also reducing
available absorptive surface area.
Factor VIII deficiency (choice A) is the cause of hemophilia A. This answer is incorrect because hemophilia A is
characterized by an elevated APTT, but a normal prothrombin time, since only factor VIII is involved. Although
hemophilia A can cause GI hemorrhage and pain, a six month crisis with abdominal discomfort as the only
symptom would be extremely rare. Also, hemophilia would likely be characterized by black tarry stools rather
than diarrhea. Hemophilia A is inherited as an X-linked recessive; thus affected individuals are usually male,
while females are carriers.
Low levels of factor IX (choice B) is the cause of Christmas disease. Like hemophilia A, factor IX deficiency is
characterized by prolonged APTT and normal prothrombin time. Specific coagulation factor assays distinguish
these two diseases, as they are otherwise identical in both presentation and inheritance.
Low levels of factors II, V, VII, IX, and X (choice D) could be characteristic of liver disease, but in such a case
both prothrombin time and APTT would be elevated. Note that in liver disease, all other factors (except for
Factor VII) would also be low.
Low levels of von Willebrand's factor (choice E) cause a prolonged or normal APTT, a normal prothrombin time,
and a prolonged bleeding time. Von Willebrand's disease is inherited in an autosomal dominant pattern with
incomplete penetrance.
A 50-year-old man is brought to the emergency room with substernal chest pain. An electrocardiogram is
performed, which demonstrates ST segment elevation and T wave inversion. Several hours later the patient
develops an arrhythmia. The electrocardiogram shows random electrical activity without recognizable QRS
complexes. Which of the following descriptions best describes this arrhythmia?
A. Accelerated idioventricular rhythm
B. Accelerated junctional rhythm
C. Premature ventricular contraction
D. Ventricular fibrillation
E. Ventricular tachycardia
Explanation:
The correct answer is D. The rhythm described is that of ventricular fibrillation, which is a feared complication of
myocardial infarction that must be corrected immediately (CPR, defibrillation, IV and intracardiac drugs
including epinephrine, lidocaine, or procainamide) if the patient is to survive.
In an accelerated idioventricular rhythm (choice A), a normal latent pacemaker in the ventricles depolarizes at a
regular, accelerated rate of 50 to 100/min, each time producing unusually shaped (but similar to each other)
QRS complexes. P waves related to the complexes are not seen.
In an accelerated junctional rhythm (choice B), the P waves are typically inverted and may precede, follow, or
be hidden within regular QRS complexes that occur at a rate of 60 to 150/min.
In a premature ventricular contraction (choice C), an ectopic ventricular pacemaker inserts an ectopic beat
(typically with a wide and bizarre QRS complex) before the next sinus beat occurs.
In ventricular tachycardia (choice E), wide and bizarre, but recognizable, QRS complexes occur at an
accelerated rate.
A 62-year-old female is brought to the emergency room by her husband with complaints of shortness of breath.
Which of the following physical findings would be the most reliable indicator that she is experiencing heart
failure?
A. A third heart sound (S3)
B. A fourth heart sound (S4)
C. Ascites
D. Orthopnea
E. Pulmonary rales
Explanation:
The correct answer is A. A third heart sound (S3) is a low-pitched sound occurring at the termination of rapid
filling. In patients over 40 years of age, the appearance of a third heart sound strongly suggests congestive
heart failure. It also occurs in patients with atrioventricular valve incompetence and can be a normal finding in
some young athletes.
A fourth heart sound (S4; choice B) can be a normal finding in some older patients who do not have congestive
heart failure.
Ascites (choice C) can also occur in patients with renal, hepatic, or local conditions not associated with cardiac
factors.
Both orthopnea (choice D) and pulmonary rales (choice E) often occur secondary to heart failure, however,
they both are associated with noncardiac disorders as well.
An unrestrained driver sustains a blunt chest injury in an automobile accident, and is taken to the emergency
room. The emergency room physician wants to determine if the heart was bruised when he collided with the
steering wheel. The levels of which of the following creatine kinase isoenzymes or combinations of creatine
kinase isoenzymes would be most useful for this determination?
A. BB isoenzyme
B. MB isoenzyme of creatine kinase
C. MM isoenzyme of creatine kinase
D. Total creatine kinase and the MB isoenzyme
E. Total creatine kinase and the MM isoenzyme
Explanation:
The correct answer is D. The MB isoenzyme of creatine kinase is associated with heart damage; the MM
isoenzyme is associated with muscle damage; and the BB isoenzyme is associated with brain damage. Actually,
most tissues contain a mix of creatine kinase isoenzymes, but one species often predominates. In the case of
myocardial infarction not occurring in the setting of trauma, either total creatine kinase, or, preferentially, the
MB isoenzyme can be used for monitoring. However, in a complex setting such as in this case, where there is
known skeletal muscle damage secondary to trauma, the ratio of the MB isoenzyme to total creatine kinase is
most informative.
An emphysema patient is breathing quickly and shallowly. A friend tells the patient that he is breathing too fast,
and suggests the patient instead breathe deeply and slowly. The patient complies, then begins to turn blue. What
happened?
A. The decreased compliance of the alveoli collapses them
B. The decreased compliance of the large airways collapses them
C. The increased compliance of the alveoli collapses them
D. The increased compliance of the large airways collapses them
E. Changes in compliance play no role in the observed pathophysiology
Explanation:
The correct answer is D. In emphysema, the compliance of both the lung parenchyma and the weakened
bronchi is markedly increased. This change in compliance can create the paradoxical situation that forced
expiration may compress the larger airways (dynamic compression), trapping air in the alveoli, rather than
allowing air exchange. Thus, the best breathing strategy for these patients is taking short, rapid breaths that do
not cause collapse of airways.
Changes in alveolar compliance (choices A and C) are not implicated in this phenomenon.
Decreased compliance of the large airways (choice B) would make dynamic compression less likely to occur.
Choice E is incorrect, as changes in airway compliance are fundamental to the observed pathophysiology.
A 45-year-old male complains of gradual weight gain over the past several years. His fingers have enlarged so
much that he can no longer wear his wedding ring. He sweats more than usual, and in particular, his hands are
constantly sweaty. He has also noticed a gradual coarsening of his facial features. An MRI reveals the presence
of a 1.5-cm tumor in the anterior pituitary. Which of the following endocrine abnormalities is likely to be present?
A. Decreased plasma growth hormone concentration
B. Decreased plasma IGF-1 concentration
C. Decreased plasma insulin concentration
D. Impaired glucose tolerance
E. Increased suppression of growth hormone secretion with oral glucose
Explanation:
The correct answer is D. The patient probably has acromegaly due to a growth hormone-secreting adenoma in
the anterior pituitary. Hypersecretion of growth hormone in an adult will not cause an increase in stature, since
the epiphyses of long bones have already fused. However, overgrowth of bone in the face and skull produces
the characteristic protruding jaw and forehead observed in this disorder. Soft tissue proliferation leads to a
coarsening of facial features. The hands and feet are particularly affected, producing large and thickened
spade-like fingers and toes. Excessive growth hormone decreases the sensitivity of peripheral tissues to insulin
("anti-insulin" effect). This tends to raise blood glucose and produce a compensatory hyperinsulinemia (not
decreased plasma insulin, choice C) that functions to limit the hyperglycemia. Approximately 50% of patients
with acromegaly show impaired glucose tolerance.
Plasma levels of growth hormone (choice A) and IGF-1 (choice B) are both increased in acromegaly.
Administration of oral glucose does not suppress growth hormone in acromegaly as it does in normal individuals
(choice E).
A 43-year-old woman is found to have a blood pressure of 200/140 during a routine examination for a life
insurance policy. Further examination reveals retinal hemorrhages and the electrocardiogram (ECG) shows left
axis deviation. Which of the following is most likely to be decreased in this woman?
A. Arteriolar density
B. Arteriolar wall thickness
C. Arteriolar wall-to-lumen ratio
D. Capillary wall-to-lumen ratio
E. Total peripheral resistance
Explanation:
The correct answer is A. This woman has malignant hypertension. The hypertension has caused left ventricular
hypertrophy and it is likely that hypertrophy of arteries and arterioles has occurred as well. Another
consequence of long-term hypertension is arteriolar rarefaction, i.e., dissolution and loss of arterioles. Although
the mechanism of arteriolar rarefaction is poorly understood, it is believed to result from long-term
over-perfusion of the tissues. Organs and tissues in which the vasculature has primarily a nutritive function
(e.g., brain, heart, skeletal muscle) regulate their blood flow in accordance with the metabolic needs of the
tissues. These tissues exhibit short-term autoregulation of blood flow such that the increase in blood flow
caused by elevated arterial pressure is minimized by arteriolar constriction. When the increased blood pressure
persists for weeks to months, many of the constricted arterioles close off and are resorbed. Therefore, the