Cardio USMLE 9-22 (1)

Question 1

This patient, who recently received a diagnosis of congestive heart failure with a reduced ejection fraction, is taking a diuretic. It is very likely a potassium-sparing diuretic, such as spironolactone, because potassium-sparing diuretics are mainstays in the management of this patient’s type of heart failure. Additionally, this patient is presenting with symptoms of hyperkalemia (ascending flaccid muscle paralysis) and ECG changes that are reflective of hyperkalemia, such as peaked T waves and a widened QRS interval and sinus bradycardia.

Because spironolactone is a potassium-sparing diuretic, it will cause potassium to be reabsorbed and sodium to be excreted at higher than normal rates. Given this and the fact that some water will follow the sodium, the most likely urine findings would be?

Answer 1

low K+, elevated Na+, and a high-normal urine volume.

Because potassium-sparing diuretics reduce the secretion of potassium in the collecting ducts, more potassium will be retained and less will be excreted in the urine. Thus any answer that includes no change in or an increase in K+ in the urine is incorrect. Also, because diuretics work by increasing sodium excretion, any answer that includes no change in or a decrease in urine Na+ is incorrect. Also, because water will follow sodium, there would be an increased urine volume (initially), and thus any answer that includes no change in or a decrease in urine volume is incorrect.

Question 2

Potassium-sparing diuretics work by antagonizing the effects of aldosterone. They are often added to diuretic regimens to prevent hypokalemia; however, as a result, an adverse effect can be hyperkalemia. Overall, potassium-sparing diuretics will cause?

Answer 2

an increase in sodium excretion, a decrease in potassium excretion, and increase in water excretion.

Question 3

The patient, who had a recent episode of mononucleosis, is presenting with signs of hemolytic anemia (eg, increased reticulocyte count, scleral icterus, decreased hemoglobin) with pain and discoloration of the extremities. The patient’s fatigue and lethargy are likely due to?

Answer 3

IgM-mediated (cold) autoimmune hemolytic anemia. This cold anemia may manifest soon after Epstein-Barr virus infection, also known as infectious mononucleosis (IM), or mono. It may also occur in the acute stage of HIV, in Mycoplasma pneumoniae infection, and in leukemia. Agglutination of red blood cells in the periphery may result in painful gray or purple discoloration of the fingers caused by cold exposure, as seen in this patient. A patient with chronic cold agglutinin disease will have more symptoms during the colder months.

Question 4

Although similar to Raynaud phenomenon, cold agglutinin disease differs in appearance and mechanism. Raynaud phenomenon is caused by vasospasm, resulting in a triphasic color change from white to blue to red, based on vasculature response. The positive heterophile test result reinforces ?

Answer 4

the likelihood of IgM-mediated (cold) autoimmune hemolytic anemia associated with active IM. The heterophile test has a good sensitivity and an excellent specificity for IM. It normally yields a negative result once IM has resolved.

Question 5

Aplastic anemia results in pancytopenia (eg, leukopenia, anemia, and thrombocytopenia). As a result, signs of hemolytic anemia, such as scleral icterus or an increased reticulocyte count, would not be present.
A patient with disseminated intravascular coagulation would be in much more unstable condition and would be experiencing coagulopathies in the setting of sepsis, acute myelogenous leukemia, or obstetric complications.
Although IgG (warm) mediated hemolytic anemia would present with similar laboratory abnormalities, mononucleosis is strongly associated with?

Answer 5

IgM-mediated hemolytic anemia.
Paroxysmal nocturnal hemoglobinuria typically presents with dark urine during the night with partial clearing during the day.

Question 6

Cold agglutinin IgM-mediated hemolytic anemia is caused by antibodies directed to RBCs and often follows infection with Epstein-Barr virus, Mycoplasma pneumoniae, leukemia, or HIV. Patients commonly present with?

Answer 6

signs of anemia, including painful gray or purple discoloration of the fingers exacerbated by cold exposure.

Question 7

This patient has a past history of radiation therapy to the neck and now presents with a cold thyroid nodule. This information along with the fine-needle aspiration finding of a psammoma body (laminated concentric calcific spherules, the dark red circle to the lower right in the vignette image) suggests a diagnosis of?

Answer 7

papillary thyroid carcinoma (PTC).

PTC cells are characteristically large with overlapping nuclei containing finely dispersed chromatin, giving them a ground-glass appearance and central clearing, often termed “Orphan Annie-eye” nuclei, indicated by the arrow in this image. Numerous intranuclear inclusions and grooves can be seen due to invagination of the nuclear membrane (outlined in blue in this image), and psammoma bodies are commonly found.

Question 8

PTC is the most common form of thyroid cancer, with an excellent prognosis. These patients present with an asymptomatic thyroid nodule in the neck and may have a history of previous radiation exposure (eg, treatment of childhood malignancies, nuclear power plant accidents). Patients with RET and BRAF mutations are also at increased risk of PTC. Remember that psammoma bodies may be found in other neoplasms and can be memorized with this mnemonic:?

Answer 8

PSaMMoma bodies: Papillary thyroid, Serous ovary, Meningioma, and Mesothelioma.

Question 9

Anaplastic thyroid carcinoma occurs in older adults and appears histologically as poorly differentiated, pleomorphic cells on histology.
Follicular carcinoma is composed of ?

Answer 9

relatively small, uniform follicles with sparse colloid, lined with cells that are typically larger than those seen in a normal thyroid.
Medullary thyroid carcinoma appears histologically as polygonal to spindle-shaped cells with granular cytoplasm in an amyloid-filled stroma.
Thyroid lymphomas appear histologically as malignant lymphoid cells.

Question 10

This patient presents after 3 weeks of fever and weight loss and exhibits pallor, hepatomegaly, and splenomegaly. These symptoms, along with her laboratory test results, are consistent with ?

Answer 10

hemophagocytic lymphohistiocytosis (HLH), which is confirmed by the bone marrow aspiration, demonstrating hemophagocytes. Hemophagocytes (red arrow in image) are macrophages that have engulfed red blood cells (RBCs) and lymphocytes. Familial-type HLH is an autosomal recessive defect in several genes, including perforin-related genes, whereas the secondary type is frequently due to infection with Epstein-Barr virus. HLH involves the abnormal activation and proliferation of lymphohistiocytes, leading to hemophagocytosis and the upregulation of proinflammatory cytokines. The immune system becomes overstimulated and can begin attacking native cells in the bone marrow (as seen in the image in the vignette), the liver, and brain. Treatment consists of a combination of etoposide, corticosteroids, and methotrexate, although stem cell transplantation is often required.

Question 11

Ewing sarcoma usually presents in the second decade of life with fever, weight loss, bone tenderness, and pathologic fractures. This patient is only 2 years old, and bone marrow aspiration from a patient with Ewing sarcoma would not demonstrate the findings shown in the image.
Multiple myeloma presents in the elderly with renal injury, pathologic fractures, and hypercalcemia. A bone marrow aspirate would show red blood cells (RBCs) in rouleaux formation, stacks of RBCs pushed together by excessive protein, in contrast to this patient’s findings.
Neuroblastoma manifests with?

Answer 11

constitutional symptoms (fever, weight loss, pallor, hepatosplenomegaly), hypertension, abdominal pain, and an abdominal mass. These symptoms are not consistent with this patient’s presentation.
Wilms tumor manifests as an asymptomatic flank mass and/or gross hematuria.
Autoimmune lymphoproliferative syndrome is a rare inherited disorder of apoptosis, which is most commonly due to mutations in the FAS gene. Like HLH, it presents with chronic lymphadenopathy, splenomegaly, and symptomatic cytopenias in an otherwise healthy child. Although specific tests are required to rule out this diagnosis, the ferritin level is typically less than 3000 µg/L, as opposed to the highly elevated ferritin level seen in this patient.

Question 12

Hemophagocytic lymphohistiocytosis can be identified on a bone marrow aspirate by the presence of macrophages engulfing RBCs. Treatment consists of ?

Answer 12

etoposide, methotrexate, and corticosteroids.

Question 13

This patient presents with symptoms including daytime sleepiness, cataplexy, and sleep paralysis, some of the classic symptoms of narcolepsy. Cataplexy is defined as brief episodes of bilateral weakness brought on by strong emotions such as laughing or fear, without alteration in consciousness. Sleep paralysis is an episode of partial or total paralysis that occurs at the beginning or end of a sleep cycle. Patients are often aware that they are awake but may suffer from frightening hallucinations, called hypnagogic when they occur at sleep onset and hypnopompic when they occur on awakening.

Narcolepsy is associated with low CSF levels of hypocretin-1 (orexin A) and hypocretin-2 (orexin B). These neuropeptides are produced in the lateral hypothalamus and play a function in promoting wakefulness, but are low in narcolepsy due to?

Answer 13

destruction of the neurons that produce them.
Modafinil, an atypical dopamine reuptake blocker, is used to treat narcolepsy, although its exact mechanism of action is unknown. Patients suffering from cataplexy may also be treated with sodium oxybate.

Question 14

The other medications are not used in the treatment of narcolepsy. Ethosuximide is used for managing absence seizures. Hydroxyzine is used for?

Answer 14

treating anxiety and insomnia. Prochlorperazine is a typical antipsychotic. Zolpidem is used for treating insomnia.

Question 15

Narcolepsy is characterized by daytime sleepiness, cataplexy, sleep paralysis, and hypnagogic and hypnopompic hallucinations. It is treated with ?

Answer 15

modafinil.

Question 16

This patient’s genotype and the presence of male internal genitalia are suggestive of a genotypic male who was born with ambiguous genitalia due to ?

Answer 16

a congenital 5a-reductase deficiency.

5a-Reductase converts testosterone to dihydrotestosterone (DHT), the potent androgen required for the development of male external genitalia in utero. Individuals with a congenital 5a-reductase deficiency are born with male internal genitalia (including testes) but ambiguous or female-appearing external genitalia, such that most are raised as girls. When they reach puberty, however, increasing testosterone levels cause masculinization of the external genitalia, resulting in the “penis-at-12” phenomenon. 5a-Reductase deficiency thus causes an increased testosterone/DHT ratio; luteinizing hormone levels can be normal or elevated in patients with 5a-reductase deficiency.

Question 17

17a-Hydroxylase deficiency leads to decreased sex hormone and cortisol levels with elevated mineralocorticoid levels. Tyrosinase deficiency presents with characteristics of albinism. Nicotinamide adenine dinucleotid phosphate oxidase deficiency is ?

Answer 17

characteristic of immune disorders. 21-Hydroxylase deficiency and aromatase deficiency present with male characteristics at birth.

Question 18

5α-Reductase converts testosterone to DHT, which plays a critical role in male sexual development. Congenital 5α-reductase deficiency results in?

Answer 18

male internal genitalia (including testes) but ambiguous or female-appearing external genitalia. However, at puberty, increased testosterone levels cause masculinization of the external genitalia.

Question 19

This patient is having balance and gait difficulties along with muscular weakness during activities such as rising from a chair. His family history suggests that this is an inherited disorder. This patient’s increases in laboratory values, such as his increased creatine kinase level, along with his presentation help confirm the diagnosis of Becker muscular dystrophy (BMD). Patients with BMD usually have increased lactate dehydrogenase and aldolase levels, as this patient does. AST and ALT levels are also elevated, signifying muscle disease. BMD is a milder form of Duchenne muscular dystrophy (DMD).

Patients with BMD frequently present with muscle weakness and/or cardiac disease beginning in mid-adolescence. Patients with BMD also typically have a longer survival than patients with DMD, usually through the third decade. Although both BMD and DMD result from abnormalities in the DMD gene, the effects on production of dystrophin differ.
In BMD,?

Answer 19

in-frame deletions eliminate codons without altering the reading frame. The resulting dystrophin protein maintains normal N-terminus and C-terminus with some loss of function from the missing internal amino acids. The abnormal dystrophin protein retains some function. In patients with DMD, frameshift deletions of the dystrophin gene result in severely truncated or absent dystrophin protein, resulting in a much more severe phenotype.

Question 20

Charcot-Marie-Tooth disease, another disease with muscular symptoms, is caused by a duplication mutation. Frameshift deletions result in diseases such as Duchenne muscular dystrophy. Point mutations occur in?

Answer 20

sickle cell anemia. Trinucleotide repeat expansions are seen in Huntington disease, a condition marked by motor difficulties and cognitive decline.

Question 21

BMD manifests with muscle weakness and/or cardiac disease beginning in adolescence. It is caused by?

Answer 21

DMD mutations, such as in-frame deletions, and the resulting dystrophin protein retains some residual function.

Question 22

This patient presents with a history of painless, bright red stools, nausea, vomiting, and an inability to pass gas. These symptoms suggest Meckel diverticulum with intestinal obstruction. Meckel diverticulum results from failure of the vitelline duct to obliterate, a structure that connects the developing midgut lumen to the yolk sac. The diverticulum usually lies within 2 feet of the ileocecal valve. Although normal intestinal mucosal lining may be present, ectopic gastric mucosa and pancreatic tissue is frequently found in this anomaly. Therefore, the common presenting symptom is lower gastrointestinal bleeding.

A patient with Meckel diverticulum can present with symptoms of intestinal obstruction, since individuals with this condition carry an increased risk of developing volvulus or intussusception. The arterial supply for Meckel diverticulum comes from?

Answer 22

the superior mesenteric artery, as this vessel supplies part of the gastrointestinal tract derived from midgut.

Technetium-99m (99mTc) pertechnetate scintigraphic scanning is a radionuclide study used to confirm Meckel diverticulum by demonstrating ectopic uptake in the area superior to the bladder corresponding to the anatomic location of the ileum.

Question 23

The rule of 2’s is often used to describe features of this condition: 2% of the population, 2 times as likely in males, within 2 feet of the ileocecal valve, 2 inches in length, 2 types of heterotopic mucosa, and presentation before the age of 2.
The celiac artery supplies the structures of?

Answer 23

the foregut, not the midgut. The left gastric artery originates from the celiac artery, and thus is also associated with blood flow to the foregut structures. The right and left gastroepiploic artery supplies the greater curvature of the stomach. The inferior mesenteric artery supplies the hindgut, ie, the distal one-third of the transverse colon to the upper part of the rectum.

Question 24

A Meckel diverticulum may contain ectopic gastric tissue that can be visualized by 99mTc pertechnetate scintigraphy. Complications include?

Answer 24

painless gastrointestinal bleeding and obstruction.

Question 25

The patient presents with premature pubarche (pubic and axillary hair since childhood), excess body hair, excess acne, and oligomenorrhea. This constellation of findings points toward a form of congenital adrenal hyperplasia (CAH), a genetic disorder that leads to a deficiency in one of the adrenal gland enzymes used in the pathways for synthesis of mineralocorticoids, glucocorticoids, and androgens.

The presentation of CAH depends on the enzyme that is deficient or missing. Both 21-hydroxylase deficiency and 11β-hydroxylase deficiency manifest with virilization from excess androgen production. Although both enzyme deficiencies result in low levels of aldosterone, another mineralocorticoid precursor (11-deoxycorticosterone) is secreted in excess in 11β-hydroxylase deficiency (leading to hypertension), but it is absent in 21-hydroxylase deficiency (leading to hypotension). Although there are many reasons for ?

Answer 25

syncopal episodes, low blood pressure is one of them and would support a diagnosis of 21-hydroxylase deficiency over 11β-hydroxylase.

Question 26

Congenital adrenal hyperplasias of any type are not associated with an abnormal karyotype and would not help to differentiate 21-hydroxylase deficiency from 11β-hydroxylase deficiency.
Low aldosterone levels are present in both 11β-hydroxylase deficiency and 21-hydroxylase deficiency.
All forms of congenital adrenal hyperplasia are marked by?

Answer 26

low cortisol levels, so this would not help to differentiate between them.
The zona reticularis is the innermost layer of the adrenal cortex where androgen synthesis takes place. Hypertrophy of the zona reticularis would not differentiate between the two forms of CAH, because both produce excess testosterone levels and, in some cases, lead to zona reticularis hyperplasia.

Question 27

21-Hydroxylase deficiency is marked by deficits in glucocorticoid and mineralocorticoid synthesis coupled with increased sex steroid production, and ultimately manifests with?

Answer 27

virilization and hypotension. In contrast, 11β-hydroxylase deficiency manifests with virilization and hypertension due to accumulation of a mineralocorticoid precursor.

Question 28

This HIV-positive patient’s severe upper back pain and low CD4 count, together with a finding of caseating granulomas (necrotic inflammatory infiltrate and giant cells) on a bone biopsy specimen, suggest that he has extrapulmonary tuberculosis of the spine, also known as Pott disease. The classic clinical presentation includes spinal pain, kyphosis due to compromised vertebral integrity (as shown in the image), and neurologic signs ranging from radicular pain to cord compression and paralysis. The most common sites for Pott disease are the lower thoracic and upper lumbar spine.

Like pulmonary tuberculosis, Pott disease is treated with?

Answer 28

a combination of antimycobacterial therapy, often consisting of isoniazid, rifampin, and pyrazinamide. Rifabutin is sometimes used in place of rifampin in HIV-positive patients who are receiving antiretroviral therapy. Ideally, this patient would also begin taking antiretroviral drugs.
It is important to note that individuals with Pott disease may or may not show symptoms of pulmonary tuberculosis at the time they present with back pain. Also, a negative purified protein derivative test result, as seen in this patient, is insufficient to rule out tuberculosis (pulmonary or extrapulmonary) in a patient with advanced HIV infection. This is because the suppression of CD4+ cells by HIV infection can result in anergy toward the tuberculin antigen.

Question 29

Combination chemotherapy with vincristine, doxorubicin, and dexamethasone would be warranted for multiple myeloma of the spine. Although this patient does have recent-onset back pain and lytic lesions on imaging, the caseating necrosis on the bone biopsy specimen—in the context of advanced HIV infection—is more consistent with Pott disease. Intravenous amphotericin is a potent antifungal medication. Fungal infections are more common with HIV, but this patient’s caseating necrosis on a biopsy specimen is more consistent with?

Answer 29

Pott disease. Intravenous vancomycin is appropriate treatment for coverage of methicillin-resistant Staphylococcus aureus (MRSA), which can cause epidural abscesses, but this patient’s pathogen is tuberculosis based on biopsy findings. Highly active antiretroviral therapy (HAART) should be recommended for this patient but will not treat the immediate cause of his back pain.

Question 30

Pott disease, also called tuberculosis of the spine, classically manifests with back pain, kyphosis, and neurologic signs. Like pulmonary tuberculosis, it is treated with?

Answer 30

combination antimycobacterial therapy: isoniazid, rifampin (or rifabutin), and pyrazinamide.