Uworld22 Flashcards
MOA of physostigmine?
a cholinesterase inhibitor with a tertiary ammonium structure that can reverse both the central and peripheral nervous system symptoms of anticholinergic toxicity.
Neostigmine, edrophonium, and pyridostigmine have a quaternary ammonium structure that limits central nervous system penetration.
How can Vitamin B12 deficiency cause neurologic damage?
Neurologic damage associated with vitamin B12 def classically includes subacute combined degeneration of the dorsal columns (loss of position and vibration sensation, positive Romberg sign) and lateral corticospinal tracts (muscle weakness, spastic paresis)
What is acute cholangitis?
a life threatening infection characterized by fever, right upper quadrant pain, and jaundice (Charcot triad); hypotension and altered mental status (Reynold pentad) occur in severe cases.
Acute cholangitis typically develops in the setting of biliary obstruction; common etiologies include gallstone, malignancy, and strictures.
Dilated cardiomyopathy results from?
direct damage to cardiomyocytes and consequent myocardial contractile dysfunction (systolic dysfunction), volume overload, and ventricular dilation.
Viral myocarditis is a potential cause of dilated cardiomyopathy and should be suspected in young patients who develop heart failure following a viral prodrome.
Some patients with nonsmall cell lung carcinoma harbor a chromosomal rearrangement that creates a fusion gene between?
EML4 (echinoderm microtubule associated protein like 4) and ALK (anaplastic lymphoma kinase). This results in a constitutive active tyrosine kinase that causes malignancy.
This pathophysiology is similar to chronic myeloid leukemia
MOA of zidovudine
a nucleoside reverse transcriptase inhibitor used to prevent maternal to fetal transmission of HIV during labor (when the mother is not virally suppressed).
It is a thymidine analogue that does not have the normal 3’hydroxyl group found on thymidine. Because new nucleotides are added to growing DNA chains only at the 3’hydroxyl group, the addition of ZDV into DNA results in chain termination.
What is pill esophagitis?
can be caused by tetracyclines (doxycycline), results from prolonged contact of caustic medication with the esophageal mucosa. It most often occurs in locations where the esophagus is in close proximity to other anatomic structures, such as where the proximal esophagus comes in contact with the aortic arch and the carina.
What is hemolytic uremic syndrome?
manifests with acute kidney injury, microangiopathic hemloyic anemia, and thrombocytopenia.
Labs: decreased hemoglobin and platelet count and increased bleeding time, lactate dehydrogenase, bilirubin, blood urea nitrogen, and creatinine.
Parvovirus B19 can cause what?
causes erythema infectiousum (fifth disease) in children and arthritis in adults.
Parvo arthritis can mimic rheumatoid arthritis but is usually self-resolving
What can trigger IgE-independent mast cell degranulation?
A number of meds, inclduing opiods, radiocontrast agents, and some antibiotics (eg, vancomycin), can trigger IgE independent mast cell degranulation.
Common symptoms include diffuse itching and pain, bronchospasm, and localized swelling (urticaria)
What is potter sequence?
results from a urinary tract anomaly (eg, bilateral renal genesis) that causes decreased fetal urine output and severe oligohydraminos. The lack of amniotic fluid causes increased fetal compression (eg, flat facies, limb deformity) and pulmonary hypoplasia (eg, neonatal hypoxia), which is the most common cause of death in affected neonates.
What is anticipation?
describes an inherited condition that presents earlier and with more severe disease in successive generations.
In myotonic dystrophy, increasing length of the pathogenic trinucleotide repeat expansion accounts for severe hypotonia in a neonate (congenital) and mild symptoms (eg, myotonia, facial weakness) in parent (classic [adult]).
What is rabies virus?
has a bullet shaped envelope with knob-like glycoproteins that bind to nicotinic acetylcholine receptors.
Once transmission occurs (usually due to a bite wound from an infected animal), the virus replicates locally in muscle tissue for several days or weeks before spreading in a retrograde fashion through the peripheral nerve axons to the central nervous system.
MOA of thiazolidinediones?
activate peroxisome proliferator activated receptor gamma, a nuclear receptor that alters the transcription of genes involved in glucose and lipid metabolism.
The resulting decrease in insulin resistance lowers blood glucose and can help reverse nonalcoholic steatohepatitis.
What are some common complications of psoriasis?
psoriatic arthritis, nail changes, and uveitis
An orbital floor fracture can result in?
entrapment of the inferior rectus muscle, which presents with vertical diplopia and restriction of upward movement.
In addition, the infraorbital nerve (a branch of V2) runs along the orbital floor and can be damaged, resulting in numbness and paresthesia of the upper cheek, lip, and gingiva.
How can patients with CKD and diabetes have hypoglycemia?
Insulin has both renal and hepatic clearance. In patients with advanced chronic kidney disease and diabetes mellitus, decreased renal clearance of insulin can lead to symptomatic hypoglycemia if exogenous insulin doses are not adjusted based on the change in renal function.
What is atrioventricular nodal reentrant tachycardia?
the most common type of paroxysmal supraventricular tachycardia, resulting from abnormal conduction through 2 distinct atrioventricular nodal pathways.
ECG: narrow QRS complex tachycardia with a regular rhythm and buried (not visible) P waves.
Which lymph node enlargement is concerning for malignancy?
Lymph node enlargement is most commonly due to infection-triggered cellular proliferation but can be caused by clonal expansion of malignant cells.
Enlargement of the supraclavicular lymph nodes, which drain the chest and abdomen, is unlikely to be caused by common childhood infections and is concerning for malignancy
Irreversible ischemic injury to brain tissues causes?
causes tissue digestion by hydrolytic enzymes (liquefactive necrosis). The infarcted CNS tissue is eventually replaced with a cystic astroglial scar. In other organs, lethal ischemic injury results in coagulative necrosis
A lesion in Wernicke’s area can cause?
receptive aphasia, which is characterized by well articulated, nonsensical speech paired with a lack of language comprehension (Wernicke-Word salad).
Wernicke’s area is located in the auditory association cortex within the posterior portion of the superior temporal gyrus in the dominant temporal lobe.
The middle cerebral artery supplies Broca’s area (superior division) and Wernicke’s area (inferior division)
What is exogenous thyrotoxicosis?
can be caused by suppressive levothyroxine therapy for thyroid cancer.
When exogenous thyrotoxicosis is due to levothyroxine or mixed T3/T4 supplements, thyroxine (T4) levels are elevated; triiodothyronine (T3) is produced primarily by the peripheral deiodination of T4, so T3 levels also are elevated even if the patient is taking T4 only.
What is hemoglobin C?
caused by a missense mutation that results in a glutamate residue being substituted by lysine in the beta globin chain.
This results in an overall decrease in negative charge for the hemoglobin molecule. The speed of hemoglobin movement during gel electrophoresis is hemoglobin A > hemoglobin S > hemoglobin C
what is nocardia?
a filamentous, branching, gram+, bacteria that is partially acid fast. It most commonly causes pneumonia and brain abscesses in immunocompromised patients
The optimal site for obtaining vascular access in the lower extremity during cardiac catheterization is?
the common femoral artery below the inguinal ligament. Cannulation above the inguinal ligament can significantly increase the risk of retroperitoneal hemorrhage.
Sodium glucose cotransporter 2 inhibitors MOA
decrease renal reabsorption of glucose and sodium, leading to increased urinary glucose excretion and decreased blood glucose levels.
In addition, natriuresis and osmotic diuresis lead to a small decrease in extracellular fluid volume, total body sodium content, and blood pressure.
Side effects of spironolactone
Spironolactone is an aldosterone antagonist commonly used to treat heart failure.
It has significant antiandrogenic effects and can cause gynecomastia, decreased libido, and impotence.
Eplerenone is a more selective aldosterone antagonist with fewer adverse effects
What is an aortic dissection?
Aortic dissection classically presents with severe retrosternal pain that radiates to the back. This condition develops when overwhelming hemodyanmic stress leads to tearing of the aortic intima with blood subsequently dissecting through the aortic media.
The resulting intramural hematoma can extend both proximally and distally and can compress major arterial branches and impair blood flow.
What is carotid sinus hypersensitivity?
most commonly seen in elderly men and involves an exaggerated vasovagal response to tactile stimulation of carotid sinus baroreceptors (eg, adjusting a shirt collar or necktie).
The resulting increase in parasympathetic output leads to a prolonged sinus pause that contributes to the excessive drop in blood pressure, leading to transient loss of cerebral perfusion that manifests as presyncope (eg, lightheadedness) or syncope
what are type I muscle fibers (slow twitch or red fibers)?
primarily use oxidative phosphorylation and contain high quantities of lipids, myoglobin, and mitochondria.
They are specialized in sustained, low force contraction, and their function is amplified by endurance training.
What are type II muscle fibers (fast twitch or white fibers)?
primarily use glycolysis and specialize in rapid bursts of high force contraction. Their function is amplified by resistance training.
What is polycythemia vera?
a clonal myeloproliferative disease characterized by an increased RBC mass and low erythropoietin levels.
The majority of patients with PV have a JAK2 mutation causing hematopoietic stem cells to proliferate uncontrollably.
How can polycythemia vera be differentiated from secondary polycythemia?
by the presence of leukocytosis, thrombocytosis, and/or splenomegaly.
What is the primary pathogenic mechanism for Shigella infection?
Shigella is a non-lactose fermenting organism that does not produce hydrogen sulfide on triple sugar iron agar.
Mucosal invasion is the primary pathogenic mechanism for Shigella infection, which presents with bloody/mucoid diarrhea.
How does chronic hypertension result in hypertensive nephrosclerosis?
Chronic hypertension can result in hypertensive nephrosclerosis, which is characterized by compensatory medial hypertrophy and fibrointimal proliferation; endothelial damage from elevated systemic pressure also leads to hyaline arteriolosclerosis.
The narrowed arteriolar lumens cause a progressive decrease in renal blood flow, resulting in glomerular ischemia and fibrosis (glomerulosclerosis)
What can be used to treat both BPH and hypertension?
Alpha-1 blockers such as doxazosin, prazosin, and terazosin are useful for the treatment of both benign prostatic hyperplasia and hypertension.
To minimize adverse effects and drug interactions, it is desirable to prescribe a medication that can address multiple issues at once.
Phenytoin metabolism depends on the function of?
hepatic P450 oxidases and is dose dependent. Drugs that induce hepatic microsomal enzymes (phenobarbital, carbamazepine, and rifampin) enhance phenytoin metabolism and decrease its serum concentraion.
What is the virulence factor of strep pneumo? ?
primarily due to a polysaccharide capsule.
A conjugate vaccine provides long lasting immunity against serotypes in the vaccine but provides no significant immunity against nonvaccinated serotypes.
Therefore, infection can still occur due to serotypes not covered by the vaccine.
What is kaposi sarcoma?
Kaposi sarcoma often presents as multiple red, purple, or brown lesions on the lower extremities in patients with HIV infection. It is a vascular tumor caused by human herpesvirus type 8 infection of endothelial cells.
