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