Cardio USMLE 9-26 (2)

Question 1

This patient presents with forgetfulness combined with intermittent right-sided abdominal pain, polyuria, and muscle weakness. In addition, his costovertebral angle tenderness and imaging point to the presence of kidney stones. These are the typical signs and symptoms of hypercalcemia (“Stones, bones, groans, and psychiatric overtones”). The most common causes of hypercalcemia are?

Answer 1

primary hyperparathyroidism and malignancy, which together account for over 90% of cases. While this is the “classic” presentation, in clinical practice, hypercalcemia is usually picked up on blood tests before symptoms develop.

Question 2

Calcium stones are the most common type of kidney stones (80%–85%). Although most patients who develop calcium stones have normal levels of calcium in their blood, conditions that result in hypercalcemia, such as hyperparathyroidism, can also result in calcium stone formation. Cancers, such as squamous cell carcinoma of the lung, that produce PTH-related peptide as a paraneoplastic syndrome, or multiple myeloma induce?

Answer 2

calcium stone formation too.
The stones are made of calcium oxalate or calcium phosphate and are visible on both plain film and noncontrast CT scan. This differs from uric acid stones, which are radiolucent on plain film and opaque on CT scan. Other risk factors for kidney stone formation are excessive intake of vitamin D and milk-alkali syndrome.

Question 3

Amitriptyline toxicity would promote urinary retention as well as confusion, constipation, and abdominal pain. Crohn disease can result in oxalate stone formation, where ileal involvement leads to fat malabsorption. Hyperuricemia would present with a combination of ?

Answer 3

psychiatric symptoms and kidney stones, but they would not be visible on plain film x-ray. Urinary tract staphylococcal infection with urease-positive microorganisms can result in large struvite calculi that are radiopaque.

Question 4

Calcium stones are the most common type of renal stones; they appear radiopaque on plain film x-ray. Most patients with calcium stones will be normocalcemic, but some patients may have an underlying hypercalcemia, often secondary to ?

Answer 4

hyperparathyroidism or malignancy.

Question 5

This patient presents with a testicular mass that he first noticed several months ago and begins chemotherapy. The development of shortness of breath, combined with a high FEV1/FVC ratio and increased interstitial fibrous tissue on lung biopsy, indicate that this patient has a restrictive lung disease. It is likely that this patient suffers from pulmonary fibrosis, a known complication of bleomycin, and was taking bleomycin for treatment of testicular cancer.

Bleomycin, which is active in?

Answer 5

G2 phase of the cell cycle, inhibits DNA synthesis through the generation of free radicals that bind DNA and cause strand breaks. It is used to treat testicular cancer and lymphoma. Toxicities of bleomycin include pulmonary fibrosis, minimal myelosuppression, and skin pigment changes.

Question 6

Cisplatin and busulfan cross-link DNA during active and resting phases of the cell cycle but only busulfan causes lung toxicity. It’s not used to treat testicular cancer. Methotrexate inhibits dihydrofolate reductase in the S phase of the cell cycle. Etoposide is a chemotherapy agent that is not associated with?

Answer 6

lung toxicity. The most common lung toxicity with paclitaxel treatment is interstitial pneumonitis.

Question 7

Bleomycin is a G2-phase–specific chemotherapeutic agent used to treat testicular cancer and lymphoma. It acts by?

Answer 7

inducing the formation of free radicals, which then cause DNA strand breaks.

Question 8

The first step in salivation is secretion of saliva by acinar cells of the salivary glands. Saliva has approximately the same electrolyte composition as plasma. After it is secreted, it is then modified by ductal cells as it travels along the ducts. Impermeable to water, these ductal cells reabsorb sodium and chloride and secrete potassium and bicarbonate. Normally, the final composition of saliva is hypotonic to plasma because ductal cells tend to reabsorb more solute than they secrete. As secretory flow rate increases, the saliva spends less time exposed to the ductal cells, so the electrolyte composition remains similar to that of plasma. The only exception is bicarbonate, which is actually secreted at higher rates when the flow rate increases. This is because its secretion is selectively stimulated by?

Answer 8

parasympathetic activity when flow rate increases.

In this patient, who has an increased salivary flow rate, the salivary sodium and potassium content will remain similar to that in plasma, so sodium will be increased and potassium will be decreased relative to normal salivary electrolyte levels.

Question 9

As the rate of salivation increases, less sodium is reabsorbed and less potassium is secreted. In this condition, salivary sodium will be?

Answer 9

increased while potassium will be decreased relative to normal salivary electrolyte levels.

Question 10

This patient has a history of breast cancer and now returns with a new lump found on self-exam. Her previous breast cancer was found to be positive for HER-2 receptors, and trastuzumab, a monoclonal antibody against the HER-2 receptor, was successfully utilized to treat her disease. This patient is treated with trastuzumab again for the recurrence of breast cancer, but this time the drug is ineffective.

Chemotherapy failure (“ineffectiveness of treatment regimen”) results from tumor cell resistance to the effects of anticancer drugs, similar to the resistance that bacteria develop toward antibiotics. Resistance may be intrinsic and seen early in initial treatment, or acquired and become evident only when a treatment that was originally effective proves ineffective when used again in a subsequent regimen.
There are several mechanisms by which tumor cells can acquire resistance. Because of their inherent genomic instability, cancer cells acquire many mutations over time. In this case, tumor cells survived initial therapy because of ?

Answer 10

mutations that altered the drug target. Imatinib (a tyrosine kinase inhibitor), all-trans retinoic acid, and the monoclonal antibodies are examples of other chemotherapeutic drugs that can become ineffective via this mechanism.

Question 11

Although some cancer cells may decrease activation of anticancer drugs, this is not a mechanism that can be acquired. Acquired resistance is associated with?

Answer 11

an increase in Bcl-2 expression, not decreased tumor expression of Bcl-2. The effectiveness of trastuzumab would not be altered by increased sensitivity of the tumor to estrogen. A mutation in the p53 tumor suppressor gene is a form of primary (intrinsic) resistance, not acquired resistance.

Question 12

Trastuzumab is a monoclonal antibody against the HER-2 receptor that is used to treat?

Answer 12

some breast cancers. Previously sensitive tumors can become resistant to this medication when a few remaining resistant tumor cells repopulate the tumor, similar to the process of antibiotic resistance in bacteria.

Question 13

The patient is being treated for her triple-negative ductal breast cancer with a chemotherapeutic regimen including paclitaxel, which puts her at risk of drug-induced myelosuppression. The development of a persistent fever in this patient strongly indicates that she has an infection secondary to neutropenia. To address this, her physician added granulocyte colony-stimulating factor (G-CSF) to her existing drug regimen.

G-CSF receptor is present on the surface of granulocyte precursors in bone marrow, and its activation stimulates?

Answer 13

granulocyte (white blood cell) proliferation. CD34 is a marker found on pluripotent stem cells. CD34+ cells include those from the umbilical cord and bone marrow, endothelial progenitors of the blood vessels, mast cells, and certain dendritic cells. All CD34+ stem cells have the ability to differentiate in response to chemical and/or biologic stimuli. In the hematopoietic lineage, CD34+ stem cells can be stimulated to differentiate into erythroblasts and myeloblasts using G-CSF.

Question 14

The B7 cell marker is expressed on antigen presenting cells and interacts with CD28 on T-helper cells.
CD28 is expressed on?

Answer 14

mature T-cells.
CD40 is a marker of macrophages.
CD56 is found on natural killer cells.

Question 15

G-CSF is used to stimulate granulocyte production in patients with neutropenia, and acts by binding and activating pluripotent hematopoietic stem cells. Pluripotent hematopoietic stem cells are?

Answer 15

CD34+ and CD38-, and have the capacity to differentiate into erythroblasts and myeloblasts in response to biochemical stimuli.

Question 16

This patient presents with anterior, central chest pain; shortness of breath; diaphoresis; and ST-segment elevations on an ECG. These signs and symptoms are suggestive of an acute myocardial infarction (MI). She most likely has ?

Answer 16

homocystinuria, as evidenced by the clinical picture of a tall marfanoid habitus, downward and inward lens subluxation, and an ECG-confirmed acute MI at a young age. Intellectual disability is also a common finding in patients with homocystinuria.
Untreated homocystinuria increases a patient’s risk of experiencing thromboembolic events in the third decade of life. In fact, almost one-third of patients with untreated homocystinuria die of thrombotic complications by age 30. There are three forms of homocystinuria.
Cystathionine synthase deficiency
Decreased affinity of cystathionine synthase for pyridoxal phosphate
Methionine synthase deficiency

Question 17

Cystathionine synthase converts homocysteine to cystathionine and uses vitamin B6 as a cofactor. Vitamin B6 is converted to pyridoxal phosphate, which is a cofactor used in various reactions, such as transamination, decarboxylation reactions, and glycogen phosphorylase. Treatment for cystathionine synthase deficiency is restriction of methionine and an increase in cysteine, vitamins B6 and B12, and folate in the diet.
Treatment for a decreased affinity of cystathionine synthase for pyridoxal phosphate is to?

Answer 17

increase intake of vitamin B6 and cysteine in the diet. Methionine synthase normally converts homocysteine to methionine. Treatment for a deficiency in methionine synthase includes an increase in methionine in the diet.

Question 18

Adenosine deaminase deficiency is seen in patients with a purine salvage deficiency and severe combined immunodeficiency (SCID). Patients with SCID have recurrent bacterial, viral, and fungal infections.
Glucose-6-phosphate dehydrogenase (G6PD) deficiency is common in African-American individuals, and patients with this deficiency are at risk for hemolysis and free radical inflammatory responses. Although this patient is African American, she has no evidence of hemolysis.
A deficiency in methionine synthase can cause?

Answer 18

homocystinuria; however, this reaction uses vitamin B12, not B6. Methionine synthase converts homocysteine to methionine.
Phenylalanine hydroxylase deficiency is present in patients with phenylketonuria. Symptoms include intellectual disability, musty body odor, growth retardation, fair skin, and eczema.
Pyruvate carboxylase is the first enzyme in gluconeogenesis. A deficiency in this enzyme would impair glucose synthesis.
Congenital deficiency of tyrosinase can result in albinism.

Question 19

Homocystinuria results in intellectual disability, marfanoid habitus, and lens subluxation. Untreated homocystinuria increases a patient’s risk for thromboembolic events in the third decade of life. The three types of homocystinuria are:?

Answer 19

(1) cystathionine synthase deficiency (this enzyme uses vitamin B6 as a cofactor), (2) decreased affinity of cystathionine synthase for pyridoxal phosphate, and (3) methionine synthase deficiency.

Question 20

This patient is presenting with hepatosplenomegaly and an eosinophilia with fevers, which are highly suggestive of a parasitic schistosoma infection. Eosinophilia is due to Th2-type inflammation against this extracellular parasite. High-risk behaviors include exposure to unsanitary drinking water. This patient has acute Katayama fever due to schistosomal infection acquired in Iraq. Schistosomiasis, caused by ?

Answer 20

Schistosoma mansoni, is endemic to sub-Saharan Africa, the Middle East, South America, and the Caribbean.
As illustrated in the diagram, after male and female worms mate in the host circulation, many egg forms are produced. Females produce hundreds of eggs per day, which lodge in various peripheral sites (around which granulomas form) or can be excreted in the feces. These hatched parasites migrate throughout the body producing eosinophilia and trigger Katayama fever. Schistosomiasis can be treated muscle inflammation and periorbital edema.

Question 21

Rather than causing hepatosplenomegaly, Trichinella infection would cause?

Answer 21

Trichinella infection comes from eating undercooked meat. There is no mention of this patient having been exposed to undercooked meat, nor exhibiting classic Trichinella physical exam findings. with praziquantel.

Question 22

Babesia microti, a blood parasite, is one cause of babesiosis, a malaria-like illness common in the United States and not seen in Iraq. Although babesiosis can feature a fever as seen in this patient, babesiosis rarely involves the liver. Furthermore, babesiosis, like malaria, is caused by parasites that multiply in red blood cells, causing a?

Answer 22

hemolytic anemia when replicated parasites are released. This patient’s hemoglobin and hematocrit are within normal limits, making this very unlikely.

Guinea worm disease is contracted by drinking stagnant water containing Guinea worm larvae; however, this parasite causes skin and soft-tissue infections, rather than infecting the liver and intestines.
ParasiteSoft tissueLiver

Question 23

Toxoplasmosis is caused by an infection with the parasite Toxoplasma gondii. This parasite is classically contracted by eating undercooked meat or from an individual cleaning out a cat’s litter box. An acute infection in an immunocompetent individual may cause a mild flu-like illness, however people may remain colonized with the parasite. This colonization is unlikely to cause a serious illness unless a person becomes immunocompromised. This patient’s WBC indicates that ?

Answer 23

she is not immunocompromised and she does not have a history of eating undercooked meat or cleaning up cat feces, making this answer choice unlikely.

Schistosomiasis is a parasitic fluke infection that can cause Katayama fever, characterized by fever, hepatosplenomegaly, and peripheral eosinophilia. Consider this in patients with recent travel history to the Middle East, sub-Saharan Africa, and South America with exposure to unsanitary fresh water.

Question 24

This patient presents with complaints of sleep deprivation and severe depression. She is dressed in dramatic, attention-seeking attire and behaves in an overly intimate and sexually aggressive way toward the physician and staff. She is exhibiting signs of?

Answer 24

histrionic personality disorder, one of the cluster B personality disorders (the “wild” group) that manifests early in adulthood.

It is best characterized as a pattern of excessive emotionality and attention seeking, and it is often accompanied by somatoform disorders. Somatization is a process by which an individual uses his or her body or symptoms for a range of psychologic purposes and gains, as is evident in this case by the patient reporting both sleep deprivation and depression without objective signs of either.

Question 25

An especially important characteristic to remember about histrionic personality disorder is the often overtly sexual nature of those affected. Relationships with physicians in particular are affected by the patient’s attention-seeking behavior. Patients with histrionic personality disorder consistently use physical appearance to draw attention to self and consider relationships to be more intimate than they actually are.

Type I bipolar disorder (BPD) is characterized by manic episodes, making the diagnosis unlikely. Obsessive-compulsive personality disorder is characterized by an excessive preoccupation with control, order, and perfectionism, which this patient does not demonstrate. Schizotypal personality disorder is characterized by?

Answer 25

interpersonal awkwardness, odd beliefs or magical thinking, and an eccentric appearance. Patients with borderline personality disorder show unstable interpersonal relationships, impulsivity, and inappropriate anger, none of which the patient is demonstrating. The patient in this vignette does not show grandiosity or arrogant behavior that would suggest narcissistic personality disorder.

Question 26

Histrionic personality disorder is ?

Answer 26

one of the cluster B personality disorders. It manifests early in adulthood as excessive emotionality, and attention-seeking and sexually provocative behavior.

Question 27

A young patient presents with severe cramps after physical exertion followed by passage of “red tinged” urine. She has no other symptoms. These findings are suggestive of McArdle disease. Onset of the disease typically occurs in adolescence or early adulthood and is characterized by muscle cramping, rapid fatigue, and poor endurance during exertion.

McArdle disease is a glycogen storage disorder (see table) in which?

Answer 27

myophosphorylase (an isozyme of glycogen phosphorylase) is deficient in muscle. The enzyme is responsible for liberating individual units of glucose-1-phosphate from branches of a glycogen molecule. This is most critical when the muscle is working strenuously under anaerobic conditions. When deficiency occurs, the muscle is unable to harvest sufficient glucose-1-phosphate to meet its energy needs. Subsequent muscle breakdown and release of myoglobin results in myoglobinuria (red urine).

Question 28

This patient undergoes a forearm ischemic exercise test. This test forces muscle to use glucose as fuel. In the absence of myophosphorylase, insufficient glucose-1-phosphate is liberated from muscle glycogen. Since glucose is the only cellular fuel that can be used anaerobically, there is no elevation of lactate, the product of anaerobic metabolism.
α1,6-Glucosidase is the enzyme responsible for the debranching of glycogen. It is implicated in Cori disease in which muscle cramping is not a typical feature. Cystathionine synthase is the deficient isoenzyme in patients with?

Answer 28

homocystinuria, who are at risk for atherosclerosis and vascular disease but do not typically experience muscle cramping. Glucose-6-phosphatase deficiency causes von Gierke disease, characterized by a severe fasting hypoglycemia, increased glycogen in the liver, hepatomegaly, and increased blood lactate. Lysosomal α1,4-glucosidase is the defective enzyme in patients with Pompe disease, which presents with respiratory difficulties, cardiomegaly, and progressive loss of muscle tone, leading to death early in life.
In an adolescent patient with myoglobinuria and muscle cramps during strenuous exercise, suspect McArdle disease, a glycogen-storage disorder marked by deficient skeletal myophosphorylase.

Question 29

This patient with atherosclerotic vascular disease presents with severe and continuous umbilical pain and fever. Laboratory tests reveal a leukocytosis, and occult blood is found in her stool.

The classic presentation of acute ischemic bowel disease involves rapid onset of severe periumbilical abdominal pain “out of proportion to physical examination findings.” Peritoneal signs are generally absent until late in the disease process when infarction, leading to necrosis, and sometimes perforation, has occurred. As in this patient, fever, tachycardia, and blood on digital rectal exam may be seen. Ischemic bowel disease results from intestinal hypoperfusion to all or part of the small bowel caused by emboli, arterial or venous thrombosis, or vasoconstriction from low-flow states.

Because the pathologic process involves hypoperfusion, the pain is initially diffuse and visceral. On histologic examination, one would expect to see signs consistent with irreversible cellular injury secondary to ischemia. Cell injury occurs in three stages.?

Answer 29

1. Reversible injury:

Cellular and mitochondrial swelling
Membrane blebbing
Nuclear chromatin clumping
Ribosomal detachment

2. Irreversible injury:
Rupture of lysosomes and autolysis
Plasma membrane damage
Increased mitochondrial permeability
Nuclear pyknosis (condensation)
Nuclear karyorrhexis (fragmentation)
Nuclear karyolysis (fading)

3. Cell death
   Features such as an intact cell membrane, cytoplasmic shrinkage, and membrane-bound apoptotic bodies are associated with the cellular features of apoptosis, and not cellular necrosis. Ribosomal disaggregation is an early-stage histologic finding of reversible ischemic cell injury.
   It is important to know the histologic features that distinguish necrosis from apoptosis for the USMLE step examination.

Question 30

In untreated acute ischemic bowel disease, later stages of cell injury are characterized by organelle membrane damage, cytoskeletal dysfunction, and?

Answer 30

nuclear changes, including pyknosis.