Uworld19 Flashcards
What is the major virulence factor of Strep pyogenes?
M protein, an alpha-helical coiled protein that shares structural homology with tropomyosin and myosin.
It extends from the cell wall and prevents phagocytosis, inhibits complement binding, and mediates bacterial adherence.
Antibodies against M protein form shortly after acute infection and may cross react with epitopes on myosin, leading to rheumatic carditis
Chronic lithium toxicity (eg, confusion, ataxia, neuromuscular excitability) can be precipitated by?
volume depletion and drug interactions with thiazide diuretics, ACE inhibitors, and nonsteroidal anti-inflammatory drugs
What is cyclic neutropenia?
Cyclic neutropenia occurs as a result of a mutation in the gene encoding neutrophil elastase.
This leads to accelerated apoptosis of neutrophil precursors with characteristic bone marrow findings of nuclear fragmentation and membrane blebbing.
Cyclic neutropenia is characterized by episodic (every 3 weeks), severe neutropenia that causes recurrent fever and mucositis
Why does Pseudomonas cause persistent infection in cystic fibrosis?
Patients with cystic fibrosis have thick, viscous mucus that accumulates in the airways and promotes colonization of bacteria, particularly Pseudomonas.
This gram-negative rod can produce biofilms, which act as a protective matrix that allows bacterial macrocolonies to develop, causing persistent infection.
What is the pathogenesis of Mallory-Weiss tears?
Mallory Weiss teats accounts for about 10% of cases of upper GI hemorrhage.
They occur due to increased intraluminal gastric pressure due to retching, vomiting, or other abdominal straining
What is dystonia?
a neurologic movement disorder characterized by sustained, involuntary muscle contractions that often result in abnormal, sometimes painful posturing.
Many patients can have temporary relief with the use of a sensory trick (eg, touching the face)
In the adenoma to carcinoma sequence, which gene mutation develops to malignant transformation?
The adenoma to carcinoma sequence is a series of gene mutations that leads to the development of colon adenocarincoma.
TP53 tumor suppressor gene mutation is part of the final step in the sequence and leads to malignant transformation of preexisting large adenomatous polyps.
Hypocalcemia causes?
Hypocalcemia can cause muscle cramps, perioral paresthesias, hypotension, and neuromuscular hyperexcitability.
Injury to the parathyroid glands during thyroid surgery is a common cause of hypoparathyroidism and acute hypocalcemia
What is anaphylaxis? Treatment?
type 1 (immediate) HSR involving IgE mediated mast cell and basophil degranulation.
Epinephrine is the primary treatment for anaphylaxis because it decreases further mast cell release of inflammatory mediators and counteracts existing systemic inflammatory effects (eg, shock, bronchoconstriction)
What is Ehrlichia chaffeensis?
harbored in white tailed deer and transmitted to humans by tick bite
It replicates in vacuoles within monocytes and forms mulberry-shaped, intraleukocytic inclusions (morale).
Manifestations: nonspecific symptoms (eg, fever, chills, myalgia, maculopapular rash, and significant laboratory abnormalities, particularly lymphopenia
Steady state concentration is reached in how many half lives?
During continous infusion of a drug metabolized by first order kinetics, the steady state concentration is reached in 4 to 5 half lives
Which cytokines is associated with chronic inflammation?
Chronic inflammation is associated with increased circulating pro-inflammatory cytokines (eg, IL-1, IL-6, tumor necrosis fator-alpha), which stimulates the liver to release acute phase reactants (eg, C-reactive protein, fibrinogen)
The presence of acute phase reactants increase the erythrocyte sedimentation rate, a nonspecific marker for inflammation
How are the pneumoconiosis cleared from the lungs?
The pneumoconioses are diseases resulting from the inhalation of fine dust particles that reach the respiratory bronchioles and alveoli.
Particles that lodge in this region are normally cleared by alveolar macrophages.
High particulate burden can cause the excessive release of cytokines from macrophages, resulting in progressive pulmonary fibrosis
What is illness anxiety disorder?
excessive concern about having a serious, undiagnosed disease, despite few or no symptoms and negative medical workup
5-HT3 receptor antagonists are useful for the treatment of?
visceral nausea due to gastrointestinal insults, such as gastroenteritis, chemotherapy, and general anesthesia
Antihistamines and anticholinergics are recommended for what kind of nausea?
vestibular nausea
Dopamine antagonists are useful for what kind of nausea?
nausea associated with migraine
The upper midbrain contains?
the neural structures (eg, optic nerve, pretectal nuclei, Edinger-Westphal nuclei, oculomotor nerve) that mediate the direct and consensual pupillary light reflex
What is pulmonary arterial hypertension?
a vascular complication of systemic sclerosis.
also involves fibroproliferative remodeling of the vessel wall, leading to increased pulmonary vascular resistance and right sided heart failure
Transport of glucose into the cell of most tissues occurs by the means of?
facilitated diffusion.
Glucose moves from areas of high concentration to areas of low concentration with the help of transmembrane glucose transporter proteins (GLUT). These carrier proteins are stereoselective and have preference for D-glucose.
What is reciprocal induction?
a type of signaling that occurs between two tissues that requires both be present to induce normal development.
Reciprocal induction occurs in development of the kidney (ie, between metanephric blastema and ureteric bud) and the eye (ie, between optic vesicle and surface ectoderm)
Patients with a long history of asbestos exposure are at risk for developing?
asbestosis, pleural disease and malignancies such as bronchogenic carcinoma and mesothelioma.
Bronchogenic carcinoma is the most common malignancy in this population, although mesothelioma is more specific for asbestos exposure
What is the treatment for cyanide poisoning?
Cyanide is a potent mitochondrial toxin that binds to the ferric ion in the heme center of cytochrome c oxidase.
This blocks the electron transport chain and uncouples oxidative phorsphorylation.
Hydroxocobalamin, an antidote for cyanide poisoning, rapidly binds to cyanide and forms the nontoxic metabolite cyanocobalamin, which is excreted in the urine
What is accumulation effect?
The concept of accumulation effect can be applied to disease pathogenesis and exposure to risk modifiers.
Cumulative exposure to a risk factor or risk reducer must sometimes occur for prolonged periods before a clinically significant effect is detected
What is metemoglobinemia?
Acquired methomoglobinemia can be precipitated by benzocaine and result in the conversion of Fe2+ to Fe3+, which results in functional anemia and a left shift of the oxygen-dissociation curve.
Patients have cyanosis that does not improve with supplemental oxygen.
Approximately 25% of patients with active TB have false negative tuberculin skin testing (anergy) due to?
an impaired cell mediated immune response. These individuals are at greater risk for severe, disseminated disease and death.
False negative TST can also be seen with immunocompromise, improper injection technique, and recent infection
What is paroxysmal nocturnal hemoglobinuria?
due to a gene defect that leads to uncontrolled complement-mediated hemolysis.
The classic triad: hemolytic anemia (hemoglobinuria), pancytopenia, and thrombosis at atypical site
Chronic hemolysis can cause iron deposition in the kidney (hemosiderosis)
What is tetralogy of Fallot?
Severe tetralogy of Fallot is a ductal-dependent lesion that requires blood flow through the ductus arteriosus (from the aorta to the pulmonary artery) for adequate oxygenation.
Prostaglandin E1 prevents closure of the ductus arteriosus and should be immediately administered to all cyanotic neonates with suspected ductal-dependent lesions
What is pneumocystis pneumonia? treatment?
Pneumocystitis pneumonia is common in patients with advanced HIV and usually presents with slowly worsening cough and dyspnea, hypoxia, and bilateral interstital infiltrates.
Diagnosis requires visualizing the organism in respiratory secretions using special stains (eg, methenamine silver stain).
First line treatment is trimethoprim-sulfamethoxazole
Sickle cell disease and its relation with the spleen
Sickle cell disease is characterized by repeated splenic infarctions that ultimately result in splenic atrophy and fibrosis, a process that is typically complete by late childhood/adolescence.
After autosplenectomy, patients are predisposed to infections with encapsulated bacterial organisms
an MCV>110 is highly suggestive of?
megaloblastic anemia, such as that caused by folic acid or vitamin B12 def.
Patients with chronic hemolytic anemia have increased folic acid requirements due to increased erythrocyte turnover and are predisposed to developing macrocytosis
What are the electrolyte abnormalities in primary adrenal insufficiency?
Patients with type 1 diabetes are at increased risk for other autoimmune endocrinopathies, including primary adrenal insufficiency (Addison disease).
Electrolyte abnormalities in primary adrenal insufficiency include hyponatremia, hyperkalemia, hyperchloremia, and nonanion gap metabolic acidosis
What is decreased during exercise?
Exercising muscles can receive up to 85% of the total cardiac output during periods of strenuous activity.
Although sympathetic discharge during exercise causes increased cardiac output and splanchnic vasoconstriction, there is only a modest increase in mean blood pressure as vasodilation within active skeletal muscles significantly decreases the total systemic vascular resistance.
Perianal sensation is carried by which nerve roots?
S2-S4
Compressive lesions (eg, disk herniation, tumors) affecting the L1-L5 vertebral levels can impinge upon the conus medullaris and/or T12-S4 nerve toots, causing?
radicular low back pain, changes in bowel/bladder function, saddle/perianal anesthesia (eg loss of anocutaneous reflex), and lower extremity weakness
Patients who require stem cell transplantation due to a congenital genomic disease typically receive donor cells from?
matched unrelated donor cells because they will have matched human leukocyte antigen alleles but will not have the genomic mutation that caused the condition
Thyrotoxicosis can cause?
Thyrotoxicosis, whether due to endogenous hyperthyroidism or over-replacement with thyroid hormone in patients with hypothyroidism, causes a hyperadrenergic state that can lead to atrial fibrillation, high output heart failure, and worsening of angina pectoris
The accuracy of screening or diagnostic tests is quantified by?
the area under the ROC curve (AUC).
The more accurate the test is (ie, higher sensitivity and specificity), the closer the AUC value is to 1.
Tests with higher AUCs are more accurate than tests with lower AUCs.
The primary mechanism underlying cytotoxic (early) edema following cerebral ischemia is?
the accumulation of intracellular Na+ and water due to the failure of ATP-dependent ion transporters in hypoxic cells.
Cerebral edema causes progressive neurologic decline by raising intracranial pressure, which can directly damage neural tissue or result in mechanical damage due to brain herniation
