Uworld 3 Flashcards
What is the treatment of Graves ophthalmopathy?
Glucocorticords improve Graves ophthalmopathy by decreasing the severity of inflammation and reducing the excess extraocular volume.
Recurrent sinopulmonary infections and exocrine gland fibrotic atrophy in a young patient are suggestive of what disease?
Cystic fibrosis
Cystic fibrosis can lead to what manifestations?
Pancreatic insufficiency, fal malabsorption, and a deficiency of vitamins DEAK.
Vitamin A maintains what? Deficiency causes?
Vitamin A maintains orderly differentation of specialized epithelia, including the mucus-secreting columnar epithelia of the ocular conjunctiva, respiratory and urinary tracts, and pancreatic and other exocrine ducts.
Avitaminosis A can cause squamous metaplasia of such epithelia to a keratinizing epithelium.
What is the gold standard for syphilis diagnosis?
Patients with early syphilis (eg, chancre) often have false-negative initital serologic testing.
Direct visualization of the orgranism (Treponema pallidum) by dark-field microscopy or fluorescent antibody testing is the gold standard for diagnosis but is not widely available.
What nerves enter the orbit via the superior obital fissure?
CNIII: oculomotor
CNV1: opthalmic
CNIV: trochlear
CNVI: abducens
How long can patients have viable sperm after a vasectomy?
Following vasectomy, viable sperm remain in the portion of the vas deferens distal to the transection.
Patients can still have viable sperm in the ejaculate for up to 3 months and at least 20 ejaculations after the procedure.
What is seen in sertoli-leydig cell tumors?
Sertoli-Leydig cell tumors of the ovary arise from the sex cord stroma and secrete testosterone.
Therefore, patients typically have signs and symptoms of hyperandrogenism, including rapid-onset virilization (eg, hirsutism, clitoromegaly, voice deepening) and amenorrhea.
What is purulent pericarditis caused by? Which organism is most common?
Purulent pericarditis is usually caused by hematogenous dissemination from distant infection or direct extension from an adjacent infection or chest wall trauma.
Staph aureus is the most common pathogen, particularly in the setting of a portal from the skin to the bloodstream (eg, catheter) or pericardium (eg. recent chest surgery, penetrating injury)
What is the most common cause of death in patients with diabetes mellitus?
Coronary heart disease
Patients with what disease are at the same risk of cardiovascular events (eg myocardial infarction, stroke) as patients with known coronary heart disease?
Patients with noncoronary atherosclerotic disease, diabetes mellitus, or chronic kidney disease.
What is the disease inheritance pattern for classical galactosemia?
Autosomal recessive
Autosomal recessive disorders affect what percentage of offspring?
Affect 25% of offspring of asymptomatic heterozygous carrier parents
How does classical galactosemia presents?
classical galactosemia is the most common and severe galactosemic disorder and presents within days of birth with jaundice, vomitting, and hepatomegaly.
What is hereditary angioedema due to?
Hereditary angioedema is characterized by recurrent episodes of cutaneous and/or mucosal swelling due to C1 inhibitor deficiency.
What is low in hereditary angioedema?
C4 levels are low due to uninhibited cleavage of C4 by excess activated C1.
High-output heart failure results from what?
High-output heart failure results from markedly decreased systemic vascular resistance (eg, large arteriovenous fistula) that leads to increased venous return and increased cardiac output.
Despite a sustained increased in cardiac output, the left ventricle is unable to keep up with the increased venous return, and decompensated heart failure develops.
What are the most common bacterial causes of acute otitis media?
The most common bacterial causes are respiratory colonizers: strep pneumo, haemophilus influenzea, and moraxella catarrhalis
What is the pathogenesis of acute otitis media?
Acute otitis media usually occurs after a viral upper respiratory infection causes obstruction of the eustachian tube. This obstruction leads to the accumulation of secretions, which encourages bacterial growth.
Aminoglycoside (eg, gentamicin) resistance is most commonly due to what?
Most commonly due to antibiotic-modifying enzymes. These enzymes add chemical groups to the antibiotic, which diminishes its ability to bind to the 16S ribosomal RNA within the 30s ribosomal subunit.
What is the most common diaper rash and the treatment?
Irritant contact diaper dermatitis is the most common diaper rash and is characterized by skin barrier breakdown as a result of exposure to fecal bacteria that causes increased local skin pH.
Treatment is with a barrier ointment that prevents skin contact with urine and stool.
What can be used to treat bradyarrhythmias?
Conduction impairment is common with acute inferior wall myocardial infarction.
Sinus bradycardia often occurs due to nodal ischemia and an increase in vagal tone triggered by infarction of myocardial tissue; the enhanced vagal tone can be counteracted by the anticholinergic effects of atropine.
What is the MOA of beta blockers?
Beta blockers inhibit release of renin from renal juxtaglomerular cells through antagonism of beta-1 receptors on these cells.
Inhibition of renin release prevents activation of the renin-angiotensin-aldosterone pathway, which results in decreased vasoconstriction and decreased renal sodium and water retention.
Fructose 2,6 bisphosphate (F2,6BP) activates what?
Activates phosphofructokinase-1 (increasing glycolysis)
Fructose 2, 6-bisphosphate (F2, 6BP) inhibits what?
Inhibits fructose 1,6-bisphosphatase (decreasing gluconeogenesis)
What will increase Fructose 2, 6-bisphosphate (F2, 6BP)?
phosphofructokinase-2 increases Fructose 2, 6-bisphosphate (F2, 6BP) levels in response to insulin
What will decrease Fructose 2, 6-bisphosphate (F2, 6BP)?
fructose 2,6-bisphosphatase decreases F2,6BP levels in response to glucagon.
Supraspinatus primary role?
Primarily an abductor of the arm
What is the most commonly injured structure in rotator cuff syndrome?
tendon of the supraspinatus muscle
What are the binding receptors of norepinephrine?
a1>b1>b2
Norepinephrine potently stimulates alpha-1 receptors to cause peripheral vasoconstricton, increasing systemic vascular resistance and blood pressure.
This triggers a baroreceptor-mediated reflexive decrease in heart rate that completely offsets or overrides the direct beta-1 mediated increase in heart rate caused by norepinephrine, resulting in overall unchanged or slightly decreased heart rate.
The presence of viral HBsAg and HBcAg on the cell surface stimulates what?
Hep B virus does not have a cytotoxic effect itseslf; however, the presence of viral HBsAg and HBcAg on the cell surface stimilate the host’s cytotoxic CD8+ T lymphocytes to destroy infected hepatocytes
Guillain-Barre syndrome is caused by?
An acute, demyelinating polyneuropathy thought to be caused by molecular mimicry. Antibodies formed against infectious agents cross-react with myelin and Schwann cells, leading to immune-mediated demyelination.
What is seen on light microscopy for Guillain-Barre?
Segmental demyelination and an endoneurial inflammatory infiltrate composed of lymphocytes and macrophages
Intracelluar bacterial organisms such as Legionella pneumophila are primarily countered by the cell-mediated immune response. Intracellular pathogens that replicate within phagosomes (eg, Legionella, Mycobacterium tuberculosis) triggers what?
Activation and differentiation of T-helper subtype 1 cells with subsequent macrophage activation via interferon-gamma.
Growth hormone has indirect effects mediated by what?
Mediated by insulin-like growth factor-1 secretion from the liver
What is gigantism?
Caused by excess growth hormone during childhood and is characterized by accelerated linear growth, prognathism, and bony enlargement of the hands and feet.
GH excess after closure of the epiphysial growth plates causes acromegaly.
Transudative effusions are typically caused by?
Alterations in hydrostatic or oncotic pressure (eg, heart failure, cirrhosis, nephrotic syndrome)
Exudative effusions are typically result from?
Inflammation and consequent increased vascular membrane permeability (eg, infection, malignancy, rheumatologic disease)
Exudative effusions are characterized by?
A high ratio of pleural fluid to serum total protein (>0.5) or lactate dehydrogenase (>0.6), or high absolute levels of lactate dehydrogenase
What are the major risk factors for esophageal squamous cell carcinoma?
Smoking
Excessive alcohol consumption
Intake of foods containing N-nitroso compounds
What are the traits of coccidioides immitis?
A dimorphic fungus endemic to the southwestern US.
Exists in the environment as a mold (with hyphae) that forms spores. These spores are inhaled and turn into spherules in the lungs
Allergic contact dermatitis (eg nickel allergy) is characterized by what?
type IV HSR characterized by epidermal intercellular edema (ie, spongiosis) and an inflammatory infiltrate (eg lymphocytes, eosinophils)
Clinical findings: vesicles, erythema, and pruritis for acute lesions and lichenification for chronic lesions
The foramen ovale is patent in approx 25% of normal adults. Although the foramen ovale usually remains functionally closed, transient increases of right atrial pressure above left atrial pressure can produce what?
A right to left shunt, leading to paradoxical embolism of venous clots into the arterial circulation.
Carrier-mediated transport includes facilitated diffusion and active transport. Movement of substrate across the cell membrane by these mechanisms depends on the presence of what?
Carrier proteins that can become saturated at high substrate concentrations
What is vulnerable to injury in the posterior triangle of the neck?
The spinal accessory nerve
Injury to the spinal accessory nerve results in?
Weakness of the trapezius muscle, which presents with drooping of the shoulder, impaired abduction of the arm above 100 degrees, and lateral displacement of the scapula
What antiarrhythmic class cause the most QT prolongation?
Class 1A and class III
MOA of class 1C antiarrhythmic agents (flecainide)?
Block the fast sodium channels responsible for ventricular depolarization (phase 0), prolonging QRS duration with little effect on the QT interval
Asbestos-related pleural disease is characterized by?
pleural plaques (focal pleural thickening, typically with calcifications)
Common occupational exposures: shipbuilding, insulation manufacturing and application, and drywall application
Most affected patients remain asymptomatic for 20-30 years following initial exposure
Actin is bound to what in a sarcomere?
Thin (actin) filaments in the I band are bound to structural proteins at the Z line
Myosin is bound to what in a sarcomere?
Thick (myosin) filaments in the A band are bound to structural proteins at the M line
The spleen is of what origin?
Mesodermal origin (dorsal mesentery)
The blood supply of the spleen is from what origin?
Splenic artery is derived from the major foregut vessel, the celiac trunk.
The majority of left ventricular blood flow occurs during when?
During ventricular systole, the coronary vessels supplying the left ventricle are compressed by the surrounding muscle.
As a result, the majority of left ventricular blood flow occurs during diastole.
What portion of the left ventricle is most prone to ischemia and infarction?
The systolic reduction in coronary blood flow is greatest in the subendocardial region, making this portion of the left ventricle most prone to ischemia and infarction.
What is the MOA of buprenorphine?
Buprenorphine is a partial opioid receptor agonist that binds with high affinity but has low intrinsic activity.
In patients on long-term opioid therapy, buprenorphine can displace other opioids and precipitate withdrawal.
What are 4 normal age-related changes in the liver?
- Decreased size
- Decreased perfusion
- Slower regenerative capability
- The development of yellowish-brown lipofuscin inclusions within hepatocytes
Intracellular pathogens are eliminated how?
Intracellular pathogens such as Listeria are largely eliminated by the cell-mediated immune response (eg, T-cells, macrophages, cytokines)
Patients with impaired cell-mediated immunity are at risk for invasive Listeria infections
What are the traits of Listeria monocytogenes?
Facultative, intracellular, G+ rod that produces a very narrow zone of beta hemolysis on blood agar, shows tumbling motility at room temp, and can grow at refrigerated temps
Bacillary angiomatosis is primarily seen in what patients?
Patients with advanced AIDS
How is bacillary angiomatosis transmitted?
Caused by G- bacterium Bartonella henselae, typically transmitted by a cat scratch
What is seen in bacillary angiomatosis?
Patients usually develop highly vascular, violaceous, cutaneous lesions over weeks or months.
Histo: large endothelial cells forming small vascular channels with a surrounding inflammatory infiltrate
What can be used as an early marker of abnormal phosphate metabolism in patients with CKD?
FGF23 (fibroblast growth factor-23)
What is the role of fibroblast growth factor 23?
FGF23 is secreted in response to hyperphosphatemia and lowers plasma phosphate by reducing intestinal absorption and renal reabsorption of phosphate.
What happens to phosphate in patients with chronic kidney disease?
Patients with CKD can develop hyperphosphatemia due to decreased filtration of phosphate
What are the effects of acute ethanol and acetaminophen?
Acetaminophen and ethanol are metabolized by the same cytochrome P450 enzyme.
Through competitive inhibition, acute ingestion of ethanol can lead to decreased conversion of acetaminophen to N-acetyl-p-benzoquinone imine (a toxic metabolite), potentially reducing acetaminophen-induced heptatotoxicity.
What are the effects of chronic ethanol and acetaminophen?
Acetaminophen and ethanol are metabolized by the same cytochrome P450 enzyme.
Cytochrome P450 2E1 activity is unregulated by chronic ethanol use. As a result, chronic alcohol consumption increases NAPQI concentrations and the risk of hepatotoxicity during an acetaminophen overdose.
What is protein A?
Protein A is a virulence factor found in the peptidoglycan cell wall of Staph aureus that binds to the Fc portion of IgG, leading to impaired complement activation, opsonization, and phagocytosis
Drug of choice for treatment-resistance schizophernia?
The antipsychotic clozapine
Adverse effects of clozapine
Treatment requires monitoring of the absolute neutrophil count due to the risks of neutropenia and agranulocytosis
Chronic lung transplant rejection is due to what?
Due primarily to progressive scarring of the small airways, leading to bronchiolitis obliterans.
Manifestations occur months or years after transplantation and include obstructive lung disease (eg, reduced FEV1) with dyspnea and dry cough.
What is the relation of osteoclasts and Paget’s?
Paget’s disease of bone is characterized by increased numbers of abnormal osteoclasts, excessive bone turnover and disorganized bone remodeling.
What plays a role in osteoclast differentiation?
Osteoclasts originate from hematopoietic progenitor cells. Macrophage colony-stimulating factor and receptor for activated nuclear factor kappa-B ligand (RANK-L) play an important role in osteoclast differentiation.
The occipital lobes is supplied by what?
Posterior cerebral arteries
Cortical blindness occurs due to what?
Due to damage to the primary visual cortex, located in the occipital lobes
What is the major virulence factor for group B strep?
GBS is a common cause of neonatal meningitis.
Its major virulence factor is a polysaccharide capsule with abundant sialic acid, which dramatically reduces the effectiveness of host defence mechanisms due to molecular mimicry.
MOA of theophylline
Theophylline is an adenisone receptor antagonist and indirect adrenergic agent with a narrow therapeutic index.
It is predominantly metabolized by the hepatic cytochrome oxidases. Inhibition of these enzymes by concurrent illness (eg, infection with fever) or ingestion of certain drugs or substances (eg, ciprofloxacin) can raise serum theophylline concentrations and cause toxiciity (eg seizures, cardiac arrhythmias).
What does angiotensin II do?
In the kidney, angiotensin II preferentially constricts the efferent arteriole, thereby maintaining the GFR within normal range.
What is the effect of ACE-inhibitors on GFR?
ACE-inhibitors promote efferent arteriolar dilation, causing GFR reduction.
What is seen in multiple endocrine neoplasia type 2B?
Medullary thyroid cancer
pheochromocytomas
mucusal neuromas
Marfanoid habitus
What are the physiological forces on lungs and chest wall?
The lungs exert collapsing force, and the resting chest wall exerts expanding force.
These opposing forces are in equilibrium at the functional residual capacity and generate sustained intrapleural negative pressure that allows the lung and chest wall to move together as a combined respiratory unit.
What happens to the lungs and chest wall during a loss of intrapleural negative pressure?
Loss of intrapleural negative pressure (eg. pneumothorax) disrupts the combined system, causing the chest wall to spring outward to its equilibrium position, enlarging the hemithorax. Similarly, the lung collapses to its equilibrium position where inspiratory compliance is decreased.
What is late-stage radiation dermatitis characterized by?
Occurs months to years after radiation exposure and is characterized grossly by pigment changes, telangiectasias, and chronic ulceration.
What is the histologic changes seen in late-stage radiation dermatitis? What is it due to?
Typical histologic changes include vascular abnormalities, fibroblast proliferation, and homogenization of dermal collagen (ie, fibrosis) due to the increased expression of transforming growth factor-beta.
Patients with deficiency in the proteins that generate MACs (C5-9) will show what activity on the complement cascases?
Initial control of encapsulated bacteria is largely reliant on the formation of membrane attack complexes (MACs) due to activation of the alternative complement cascase.
Patients with deficiency in the proteins that generate MACs (C5-9) are at high risk for recurrent encapsulated bacterial infection; evaluation will show reduced activity of the classical (CH50) and alternative (AH50) complement cascades.
What provides sensory innervation to the cheek?
CNV2: maxillary division of the trigeminal
CNV2 maxillary division of the trigeminal passes through what?
It passes through the foramen rotundum, then the pterygopalatine fossa, and then exits the maxilla through the infraorbital foramen.
Nerve blocks to prove anesthesia to the cheek is performed where?
At the infraorbital foramen
How does pulmonary arteriovenous malformations cause hypoxemia?
Pulmonary arteriovenous malformations cause hypoxemia through right to left shunting that is refractory to supplemental oxygenation.
The shunt can be visualized during pulmonary angiography, which demonstrates direct communication between the inflow artery and outflow vein.
What is hibernating myocardium?
Hibernating myocardium refers to the presence of left ventricular systolic dysfunction due to reduced coronary blood flow at rest that is partially or completely reversible by coronary revascularization.
What is seen in osteoarthritis of the hands?
Osteophyte formation leading to hard bony enlargement of the distal interphalangeal joints (Heberden nodes) and proximal interphalangeal joints (Bouchard nodes). Brief morning stiffness may be present.
Motor and sensory deficits across multiple peripheral upper extremitiy nerves (eg, radial and median) indicate a lesion where?
In the brachial plexus proximal to the formation of the terminal branches. In the absence of a history of trauma or malignancy, the most likely cause is nerve root compression due to cervical spondylosis (cervical radiculopathy)
Although hyperphenylalaniemia is most commonly due to phenylketonuria, progressive neurologic injury despite appropriate treatment (phenylalanine-restricted diet, tyrosine supplementation) should raise concern for what?
Impaired tetrahydrobiopterin synthesis.
This distinct disorder of phenylalanine metabolism is often due to dihydropteridine reductase deficiency, resulting in the inability to synthesize critical neurotransmitters (eg, dopamine, serotonin)
What is a struma ovarii?
An ovarian germ cell tumor composed of >50% mature thyroid tissue that can secrete thyroid hormone.
Therefore, struma ovarii can be a rare cause of thyrotoxicosis (eg weight loss, irregular menses, low TSH level)
MOA of cyproheptadine
An antihistamine with antiserotonergic properties that can be used as an antidote in severe cases of serotonin syndrome that do not respond to supportive measures
What is seen on histo for ectopic pregnancy?
Ectopic pregnancy should be suspected in patients with a pregnancy of unknown location (ie, no visible intrauterine gestation) and abnormally rising b-hCG levels.
Despite their extrauterine location, ectopic pregnancies promote endometrial decidualization, which appears as dilated, coiled endometrial glands and vascularized, edematous stroma.
Blood supply to the inferior left ventricular wall is determined by coronary dominance. Most patients have right-dominant circulation, in which the inferior LV wall is supplied by what?
right coronary artery.
Blood supply to the inferior left ventricular wall is determined by coronary dominance. 10% patients have left-dominant circulation, in which the inferior LV wall is supplied by?
left circumflex artery
The right ventricle of the heart is supplied by?
right coronary artery.
General sensation from the anterior 2/3 tongue is carried by?
mandibular division of trigeminal nerve (CN V3)
