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Question 1

Chronic hyperglycemia in patients with diabetes can lead to?

Answer 1

increased permeability and arteriolar obstruction in retinal vessels.

The resulting ischemia stimulates production of vascular endothelial growth factor and other angiogenic factors, leading to neovascularization (proliferative diabetic retinopathy).

Complications include retinal hemorrhage, retinal detachment, and vision loss.

Question 2

Side effect of tenofovir

Answer 2

Tenofovir is a nucleotide reverse transcriptase inhibitor that is a common component of HIV therapy.

This drug is generally well tolerated by may occasionally cause damage to the proximal tubule of the kidney, leading to acute kidney injury and/or proximal tubule impairment (eg, phosphoruria, glucosuria, proteinuria, water retention).

Biopsy typically reveals a normal glomerulus and renal interstitium but damage to the proximal tubule.

Question 3

What is the most common cause of syndrome of inappropiate antidiuretic hormone (SIADH)?

Answer 3

Small cell lung cancer is a neuroendocrine malignancy associated with several paraneoplastic syndromes.

It is the most common cause of SIADH due to ectopic secretion of antidiuretic hormone. SIADH is characterized by hyponatremia, decreased serum osmolality, and urine osmolality >100 mOsm/kg H2O)

Question 4

Which tests is used to monitor warfarin?

Answer 4

Prothrombin time (PT) or International normalized ratio should be monitored regularly during treatment with warfarin.

Warfarin is an oral anticoagulant that inhibits the carboxylation of vitamin K dependent coagulation factors II, VII, IX, and X.

It is used in atrial fibrillation, deep venous thrombosis, and pulmonary thromboembolism.

Question 5

What is used to monitor unfractionated heparin?

Answer 5

activated partial thromboplastin time (aPTT).

Question 6

What is erythema multiforme?

Answer 6

target shaped, inflammatory skin lesion that typically arises in the setting of infection, particularly with herpes simplex virus or Mycoplasma pneumoniae.

It is caused by the deposition of infectious antigens in keratinocytes, leading to a strong cell mediated (eg, cytotoxic T-cell) immune response.

Question 7

What is renal artery stenosis?

Answer 7

Renal artery stenosis is most often due to atherosclerosis.

It can cause severe, refractory hypertension due to activation of the renin-angiotensin-aldosterone system.

Over time, renal atrophy may occur due to chronic oxygen and nutrient deprivation.

Histologic examination may show crowded glomeruli, tubulointerstitial atrophy and fibrosis, and focal inflammatory infilrates.

Question 8

Where is the most highly oxygenated blood in the fetus?

Answer 8

the umbilical vein, which empties directly into the inferior vena cava via the ductus venosus.

Question 9

What is REM sleep behavior disorder?

Answer 9

a parasomnia characterized by dream-enactment behaviors due to a loss of atonia during REM sleep.

Patients can usually be awakened fairly easily, are alert and oriented, and can immediately recall their dreams.

Question 10

Inherited defects involving the interferon-gamma signaling pathway result in?

Answer 10

disseminated mycobacterial disease in infancy or early childhood. Patients require lifelong treatment with antimycobacterial agents.

Question 11

What is the only manifestation of galactokinase deficiency?

Answer 11

Lenticular accumulation of galactitol in the lenses of patients with galactosemia can cause osmotic damage and development of cataracts.

Cataracts are frequently the only manifestation of galactokinase deficiency.

Question 12

What is an important adverse effect of nitroprusside?

Answer 12

Cyanide toxicity; blockage of mitochondrial electron transport leads to impaired oxygen utilization, causing lactic acidosis, neurologic dysfunction, and cardiovascular collapse.

Question 13

What causes schistocytes (helmet cells)?

Answer 13

Schistocytes (helmet cells) are fragmented erythrocytes. They occur secondary to mechanical trauma from microangiopathic hemolytic anemias or prosthetic cardiac valves (macroangiopathic).

Intravascular hemolytic anemias are characterized by decreased serum haptoglobin levels as well as increased LDH and bilirubin.

Question 14

Diastolic dysfunction typically results from?

Answer 14

Diastolic dysfunction is a common cause of heart failure with preserved ejection fraction.

It typically results from concentric left ventricular hypertrophy in response to prolonged systemic hypertension (ie, increased afterload)

Question 15

What is the treatment for cryptococcal meningitis?

Answer 15

Patients with suspected cryptococcal meningitis can be diagnosed using India ink staining of the CSF.

Treatment with amphotericin B and flucytosine is required at first, followed by long term fluconazole maintenance therapy.

Question 16

The chronic myeloproliferative disorders (polycythemia vera, essential thrombocytosis, and primary myelofibrosis) often have a mutation in?

Answer 16

Janus kinase 2 (JAK2), a cytoplasmic tyrosine kinase.

This results in constitutive tyrosine kinase activity, and consequently, in the cytokine-independent activation of signal transducers and activators of transcription (STAT) proteins (JAK-STAT signaling pathway).

Question 17

What are local adverse effects of chronic topical corticosteroid therapy?

Answer 17

cutaneous atrophy, telangiectasias, and corticosteroid induced acne.

Effects are more pronouced with high-potency corticosteroids and in areas of thin skin (eg, flexural areas)

Question 18

What is benign neonatal hyperbilirubinemia?

Answer 18

presents with jaundice and elevated indirect bilirubin levels that peak at age 2-5 days.

Pathophysiology includes bilirubin clearance by the liver due to decreased hepatic UDP glucuronosyltransferase, an enzyme responsible for bilirubin conjugation.

Question 19

What is the role of the Fc fragment of IgG?

Answer 19

Immunoglobulin contains a Fab fragment that binds to antigen and an Fc fragment that activates complement and/or interacts with immune cells.

The Fc fragment of IgG activates the classical complement cascade (constant heavy chain region 2) and serves as a ligand for the Fc receptor on phagocytes (constant heavy chain region 3).

Question 20

What is schizoid personality disorder?

Answer 20

consists of a persistent pattern of social detachment, preference for solitary activities, and constricted range of affect in social interactions.

Question 21

What is atrial flutter?

Answer 21

demonstrates rapid and regular atrial activity in a saw-toothed pattern (flutter or F waves) on ECG.

Typically atrial flutter is caused by a large reentrant circuit that traverses the cavotricuspid isthmus of the right atrium, which is the target site for radiofrequency ablation.

Question 22

What is cavernous sinus thrombosis?

Answer 22

Infection of the medial face, sinuses (ethmoidal or sphenoidal), or teeth may spread through the valveless facial venous system into the cavernous sinus, resulting in cavernous sinus thrombosis.

Patients typically present with headache, fever, proptosis, and ipsilateral deficits in cranial nerves III, IV, VI, and V (ophthalmic and maxillary branches)

Question 23

What can lower the minimum infectious dose of V cholerae?

Answer 23

Vibrio cholerae must survive the acidic environemnt of the stomach to reach the small intestine and cause disease.

Because the organism is easily destroyed by acid, a high burden of organisms must be ingested to caused infection.

However, condition that decrease gastric acidity (eg, antacid use) lower the minimum infectious dose of V cholerae by multiple orders of magnitude.

Question 24

What are signs of a patella fracture?

Answer 24

Patella fractures are most commonly due to a direct impact to the anterior aspect of the knee.

Signs include an acutely swollen knee, focal patella tenderness, inability to extend the knee against gravity, and a palpable gap in the extensor mechanism.

Question 25

What are the steps of base excision repair?

Answer 25

Base excision repair is used to correct single-base DNA defects induced spontaneously or by exogenous chemicals. In this process, glycosylases remove the defective base, and the corresponding empty sugar phosphate site is cleaved and removed by the action of endonuclease and lyase. DNA polymerase then replaces the missing nucleotide, and ligase seals the final remaining nick.

Question 26

How is prostate adenocarcinoma diagnosed?

Answer 26

Prostate adenocarcinoma is generally diagnosed with transrectal prostate biopsy, which often reveals atypical cells with enlarged nuclei and prominent nucleoli forming crowded, infiltrative glands.

Question 27

What is the hallmark of peroxisomal disorders?

Answer 27

The buildup of very long chain and branched chain (eg, phytanic) fatty acids due to impaired oxidation is the hallmark of peroxisomal disorders (eg, Zellweger syndrome, adrenoleukodystrophy). Accumulation of these fatty acids in the brain results in permanent neurologic dysfunction.

Question 28

What are the renal changes during pregnancy?

Answer 28

Pregnancy results in significant plasma expansion and widespread vasodilation, leading to increased renal plasma flow and glomerular filtration rates. Serum creatinine is reduced by approximately 0.4 mg/dL in this population; therefore, a rise in serum creatinine, even to levels that are normal in nonpregnant patients, represents significant renal dysfunction

Question 29

Function of sertoli cells?

Answer 29

Sertoli cells produce inhibin in response to FSH from the anterior pituitary. Inhibin suppresses FSH production in the pituitary. Sertoli cells also facilitate spermatogenesis within the seminiferous tubules. Impaired Sertoli cell function would lead to decreased production of inhibin, increased FSH levels, and impaired fertility.

Question 30

What is the relationship with thiazide diuretics (hydrochlorothiazide, chlorthalidone) and calcium?

Answer 30

Thiazide diuretics increase calcium absorption in the distal convoluted tubules within the nephron. Thiazides are associated with increased bone mineral density and are recommended for treatment of hypertension in patients at risk for osteoporosis.

Question 31

What is the relationship with calcium and loop diuretics?

Answer 31

Loop diuretics increase urinary calcium loss.

Question 32

Pulmonary function testing in cystic fibrosis reveals what kind of pattern?

Answer 32

obstructive pattern, characterized by a decrease FEV1/FVC ratio and an increased total lung capacity and residual volume.

Question 33

Anaphylaxis can cause distributive shock due to?

Answer 33

widespread release of inflammatory mediators (eg, histamine) that leads to massive peripheral vasodilation. Arteriolar vasodilation decreases systemic vascular resistance to cause hypotension, and venular vasodilation decreases central venous pressure and pulmonary capillary wedge pressure. Cardiac output is often increased in early distributive shock due to reduced SVR and a baroreceptor reflex-mediated increase in heart rate.

Question 34

Vesicoureteral reflex typically occurs due to?

Answer 34

due to a congenitally shortened intravesical ureter length, which prevents complete closure of the ureterovesical junction and allows retrograde urine flow into the ureter during micturition. Most cases resolve spontaneously as the length of the intravesical ureter increases with patient growth.

Question 35

Thoracentesis should be performed where?

Answer 35

below the 6th rib in the midclavicular line, the 8th rib along the midaxillary line, or the 10th rib along the paravertebral line in order to minimize the risk of lung injury. Insertion of a needle lower than the 9th rib increases the risk of penetrating abdominal structures. The needle should also be inserted along the upper border of the rib to prevent injury to the intercostal vessels.

Question 36

In patients with HIV, the presence of multiple ring-enhancing lesions with mass effect is most often indicative of what?

Answer 36

toxoplasmosis, followed by primary central nervous system lymphoma. Treatment of toxoplasmosis: pyrimethamine and sulfadiazine

Question 37

Primary central nervous system lymphoma is typically composed of?

Answer 37

B-lymphocytes

Question 38

Chronic pancreatitis may cause vitamin B12 deficiency due to?

Answer 38

decreased production of pancreatic proteolytic enzymes (eg, exocrine insufficiency), which are needed to release vitamin B12 from R protein. Other manifestations of chronic pancreatitis include chronic epigastric pain, weight loss, and steatorrhea.

Question 39

How is a highly lipophilic drug be distributed within the body?

Answer 39

Following intravenous administration, a highly lipophilic drug will be rapidly distributed to organs with high blood flow (eg, brain, liver, kidneys, lungs). The drug is then redistributed to tissues with relatively lower blood flow (eg, skeletal muscle, fat, bone). This accounts for the short duration of action of many commonly used anesthetics, such as propofol.

Question 40

What is medullary thyroid cancer?

Answer 40

a neuroendocrine tumor that arises from calcitonin-secreting C (parafollicular) cells. It is often seen in the context of multiple endocrine neoplasia type 2 (A and B), although the majority of cases are sporadic. Both sporadic and familial medullary thyroid cancers are associated with mutations in the RET proto-oncogene.

Question 41

Obstructive sleep apnea can cause?

Answer 41

Obstructive sleep apnea presents in obese individuals with excessive daytime sleepiness and signs of nocturnal upper airway obstruction (eg, snoring, gasping). The condition is associated with systemic hypertension. Prolonged, untreated obstructive sleep apnea can also cause pulmonary hypertension and right heart failure.

Question 42

Topical corticosteroids are the first line therapy for atopic dermatitis. Their MOA is?

Answer 42

decreasing tissue production of proinflammatory prostaglandins and leukotrienes through the inhibition of phospholipase A2; they also inhibit transcription of many other proinflammatory mediators

Question 43

What is cryptococcus neoformans?

Answer 43

a round/oval yeast with a thick polysaccharide capsule. It is a common cause of meningoencephalitis (eg, headache, vomiting, confusion, seizure) in patients with untreated AIDS. The yeast can frequently be visualized in the cerebrospinal fluid by India ink or silver stain.

Question 44

What is serotonin syndrome?

Answer 44

characterized by a triad of autonomic instability, altered mental status, and neuromuscular irritability. It may develop when a monoamine oxidase inhibitor (MAOI) antidepressant or a non-antidepressant with MAOI activity (eg, linezolid) is combined with a serotonergic medication such as a selective serotonin reuptake inhibitor, serotonin-norepinephrine reuptake inhibitor, or tricyclic antidepressant.

Question 45

What is the treatment of choice for diabetic ketoacidosis?

Answer 45

intravenous normal saline and insulin. These therapies increase serum bicarbonate and sodium levels, lower serum glucose and potassium levels, and decrease overall serum osmolarity.

Question 46

What can lead to poor intestinal absorption of levothyroxine?

Answer 46

Coadministration of levothryoxine with various foods (eg, soy products) and certain medications (eg, iron, calcium, antacids) can lead to poor intestinal absorption of levothyroxine and symptoms of hypothyroidism while on therapy.

Question 47

What is the major disposal pathway for waste nitrogen generated by catabolism of amino acids?

Answer 47

Ornithine transport into mitochondria is necessary for the proper function of the urea cycle, which is the major disposal pathway for waste nitrogen generated by catabolism of amino acids. Urea cycle defects typically cause neurological damage due to the accumulation of ammonia. Protein restriction improves this condition by reducing the amount of amino acid turnover.

Question 48

What are the TATA and CAAT boxes?

Answer 48

promoters of transcription in eukaryotic cells and are located approximately 25 and 75 bases upstream from the transcription start site, respectively. They promote initiation of transcription by serving as binding sites for transcription factors and RNA polymerase II

Question 49

MOA of norepinephrine?

Answer 49

stimulates beta1 adrenoreceptors, which increases cAMP concentration within cardiac myocytes and leads to increased contractility, conduction, and heart rate Peripheral vasoconstriction occurs via stimulation of alpha1 adrenoreceptors in vascular smooth muscle cells and activation of an IP3 signaling pathway

Question 50

What is malingering?

Answer 50

a behavior characterized by intentional falsification or exaggeration of symptoms to obtain an obvious external reward. The presentation is typically based on a subjective report of symptoms, and these patients commonly refuse to undergo invasive medical procedures.

Question 51

What is indication of a language delay at 18 months age?

Answer 51

Failure to say >3 words in addition to mama and dada. Initial evaluation includes audiology testing to assess for potential hearing loss

Question 52

Gas exchange between the alveoli and pulmonary capillary blood depends on both perfusion and diffusion. The exchange of O2 and CO2 in a normal individual at rest is?

Answer 52

perfusion limited, so alveolar and capillary partial pressures are equal. Situations in which O2 exchange becomes diffusion-limited (eg, emphysema, pulmonary fibrosis) cause a large gradient between alveolar and capillary PO2; PCO2 is less affected due to the greater diffusion capacity of CO2.

Question 53

Patients with amyotrophic lateral sclerosis often develop respiratory failure due to?

Answer 53

inspiratory muscle weakness (causing decreased vital capacity), expiratory muscle weakness (causing a weak cough), and bulbar dysfunction (causing dysphagia and chronic aspiration)

Question 54

What is meconium ileus?

Answer 54

a distal small bowel obstruction due to abnormally dehydrated meconium in a patient with cystic fibrosis. Persistent, treatment resistant infectious pneumonias, bronchiectasis, and cor pulmonale account for most deaths due to CF.

Question 55

Where is the ductus arteriosus derived from?

Answer 55

the sixth embryonic aortic arch.

Question 56

What can be used to close a PDA in premature infants?

Answer 56

A patent ductus arteriosus causes left to right shunting of blood that can be heard as a continuous murmur over the left infraclavicular region. Indomethacin (a PGE2 synthesis inhibitor) can be used to close a PDA in premature infants, but surgical ligation is often necessary in older patients.

Question 57

Urgency incontinence, or overactive bladder, is caused by?

Answer 57

uninhibited bladder contractions (detrusor instability) that results in a sudden urge to void followed by an involuntary loss of urine. Treatment with beta-3 adrenergic receptor activation (eg, mirabegron) relaxes the detrusor muscle, promotes urine storage, and decreases incontinent episodes.

Question 58

What is the blood supply for the ureter?

Answer 58

The proximal ureter receives its blood supply from the renal artery whereas the distal ureter is supplied by the superior vesical artery. Circulation to the middle portions of the ureter is variable and anastomotic.

Question 59

What is rheumatoid arthritis characterized by?

Answer 59

synovial hyperplasia with inflammatory infiltrates. The accelerated metabolic rate of the inflamed synovium causes local hypoxia, which leads to synovial angiogenesis. As the disease progresses, the joint space is replaced by a rheumatoid pannus (an invasive mass of fibroblast-like synovial cells, granulation tissue, and inflammatory cells) which can destroy the articular cartilage and underlying subchondral bone.

Question 60

What is alkaptonuria?

Answer 60

AR disorder caused by a deficiency of homogentisic acid dioxygenase, an enzyme involved in tyrosine metabolism. Excess homogentisic acid causes diffuse blue black deposits in connective tissues. Adults have sclerae and ear cartilage hyperpigmentation along with osteoarthropathy of the spine and large joints.

Question 61

What is a malformation?

Answer 61

refers to an abnormal body structure due to an intrinsic defect in development. Holoprosencephaly is a malformation characterized by a spectrum of fetal facial and cerebral anomalies due to incomplete division of the forebrain (prosencephalon).

Question 62

What in Hirschsprung disease causes the affected rectosignmoid region to become narrowed?

Answer 62

Absence of the submucosal (Meissner) and myenteric (Auerbach) plexuses in Hirschsprung disease causes the affected rectosigmoid region to become narrowed. The submucosa of the narrowed area is the most superficial layer where the absence of ganglion cells can be confirmed during biopsy procedures.

Question 63

Median nerve injury at the level of the carpal tunnel may result in?

Answer 63

weakness of thumb abduction, flexion, and opposition. Volar dislocation of the lunate from its normal position within the floor of the carpal tunnel can cause median nerve compression and/or injury.

Question 64

What is treatment for phthirus pubis?

Answer 64

Phthirus pubis is the human pubic louse. It is transmitted sexually via skin to skin contact and causes intense pruritus. Louse and nits (eggs) can often be visualized on examination. Treatment is with topical permethrin.

Question 65

What is the treatment for tricyclic antidepressant overdose?

Answer 65

Tricyclic antidepressant overdose can cause fatal cardiac arrhythmias and refractory hypotension due to inhibition of fast sodium channels in cardiac myocytes. Sodium bicarbonate is used to treat associate cardiac toxicity and works by increasing serum pH and extracellular sodium (alleviating fast sodium channel blockade)

Question 66

Why are neonates at risk for vitamin K deficiency?

Answer 66

primarily due to poor transplacental transfer and low content in breast milk. Because vitamin K is necessary for clotting factor activity, neonates who do not receive vitamin K prophylaxis at birth are predisposed to bleeding complications such as intracranial hemorrhage.

Question 67

What is nonbacterial thrombotic endocarditis?

Answer 67

characterized by valvular deposition of sterile platelet rich thrombi. It likely results from valvular damage due to inflammatory cytokines in the setting of an underlying hypercoagulable state, and it is most commonly seen with advanced malignancy (especially mucinous adenocarcinoma) or systemic lupus erythematosus.

Question 68

What are the hemodynamics of a patent ductus arteriosus?

Answer 68

A patent ductus arteriosus allows blood from the aorta to flow directly into the pulmonary artery, which effectively decreases systemic vascular resistance. Pulmonary overcirculation occurs with increased blood return to the left atrium and left ventricle, and the left ventricle compensates by increasing stroke volume and cardiac output.

Question 69

What is the optimal location for needle insertion during a lumbar puncture?

Answer 69

L3/L4 or L4/L5 space as this is well below the spinal cord termination site (L1 in adults). The L4 vertebral body lies on a line drawn between the highest points of the iliac crests

Question 70

MOA of carbamazepine

Answer 70

The first line treatment for trigeminal neuralgia is carbamazepine, a medication that inhibits neuronal high frequency firing by blocking sodium channels. Carbamazepine can cause bone marrow suppression; therefore, complete blood cells counts should be monitored periodically.

Question 71

What is herpetic gingivostomatitis?

Answer 71

a severe vesicular or ulcerative disease following primary infection with herpes simplex virus type 1. The diagnosis is supported by the presence of multinucleated giant cells in a Tzanck smear. Involvement of the gingiva, tongue, palate and pharynx along with systemic symptoms (eg, fever, malaise) is common. In contrast, herpes reactivation in the trigeminal ganglia generally results in mild perioral vesicles.

Question 72

Cushing syndrome caused by a pituitary adenoma or ectopic (paraneoplastic) ACTH secretion is associated with elevated ACTH levels. High dose dexamethasone suppresses ACTH and cortisol secretion when Cushing syndrome is caused by?

Answer 72

a pituitary adenoma (Cushing disease) but not when it is caused by ectopic ACTH secretion (eg, small cell lung cancer)

Question 73

What happens when NSAIDs are used with patients with intravascular volume depletion (eg, cirrhosis)?

Answer 73

Nonsteroidal anti-inflammatory drugs inhibit prostaglandin synthesis. Patients with intravascular volume depletion (eg, cirrhosis) are dependent on the vasodilatory effects of prostaglandins to maintain adequate renal plasma flow and glomerular filtration. NSAID use in this population reduces glomerular filtration rates and blunts the effects of loop diuretics, leading to sodium and water retention

Question 74

What is tuberculous meningitis?

Answer 74

characterized by formation of a thick, gelatinous exudate in the base of the brain; cerebral vasculitis; and hydrocephalus. It frequently presents with subacute, slowly progressive nausea, vomiting, fever, cranial nerve deficits, and strokes.

Question 75

Listeriosis is most commonly transmitted through?

Answer 75

food ingestions and can cause meningitis in immunocompromised adults. Listeria is a gram+ rod with tumbling motility. It grows well in cold temperatures and can therefore contaminate refrigerated food .

Question 76

MOA of adalimumab?

Answer 76

Adalimumab is a recombinant human IgG that binds tumor necrosis factor-alpha (TNF-alpha). Antidrug antibodies can develop against adalimumab (or other immunoglobulin-based anti-TNF agents) that can block its interaction with TNF-alpha, preventing the drug from functioning and leading to more rapid drug clearance.

Question 77

What is neuroleptic malignant syndrome?

Answer 77

A lifethreatning reaction to antipsychotic meds characterized by diffuse muscle rigidity, hyperthermia, autonomic instability, and altered sensorium. The antipsychotic should be stopped and supportive care provided; dantrolene, a ryanodine receptor blocker that inhibits calcium release from the sarcoplasmic reticulum, is an effective antidote.

Question 78

Friedriech ataxia is characterized by?

Answer 78

cerebellar ataxia (spinocerebellar tract degeneration) and loss of position/vibration sensation (dorsal column/dorsal root ganglia degeneration), kyphoscoliosis, and hypertrophic cardiomyopathy. Foot abnormalities and diabetes are also common.

Question 79

What is the pathogenesis of systemic sclerosis (scleroderma)?

Answer 79

involves vascular endothelial cells (increased expression of endothelin 1 and adhesion molecules), T lymphocytes (production of cytokines that activate fibroblasts) and dermal fibroblasts (increased production of collagen and ground substance)

Question 80

What are pattern recognition receptors (PRRs)?

Answer 80

PRRs are part of the innate immune response; they recognize damaged host proteins or conserved microbial molecules and trigger inflammation. Toll-like receptors, a type a PRR on macrophages and dendritic cells, recognize lipopolysaccharide and promote the release of inflammatory cytokines (eg, IL-1/6/12, TNF-alpha) via NF-kB signaling.

Question 81

What happens in HIV pol gene mutations?

Answer 81

responsible for acquired resistance to reverse transcriptase inhibitors, protease inhibitors, and integrase stand transfer inhibitors. Mutations of the env gene enable escape from host-neutralizing antibodies.

Question 82

MOA of local anesthetics?

Answer 82

diffuse through the neuronal cell membrane to block the influx of sodium into the cell. This prevents depolarization and inhibits action potential propagation

Question 83

What is the mechanism of tetanospasmin?

Answer 83

Tetanospasmin is a neuro-exotoxin released by Clostridium tetani. The toxin blocks the release of glycine and gamma-aminobutyric acid (GABA) from the spinal inhibitory interneurons that regulate the lower motor neurons. These disinhibited motor neurons cause increased activation of muscles, leading to spasms and hyperreflexia.

Question 84

How is Crohn disease associated with oxalate kidney stones?

Answer 84

Impaired bile acid absorption in the terminal ileum leads to loss of bile acids in feces with subsequent fat malabsorption. Intestinal lipids then bind calcium ions, and the resulting soap complex is excreted. Free oxalate (normally bound by calcium to form an unabsorbable complex) is absorbed and forms urinary calculi (enteric oxaluria)

Question 85

What is the most sensitive test for primary hypothyroidism?

Answer 85

The thyroid releases thyroid hormone (triiodothyronine and thyroxine) in response to TSH from the pituitary, which is regulated by thyrotropin-releasing hormone (TRH) from the hypothalamus. Thyroid hormone suppresses the secretion of TSH and TRH via negative feedback, and small changes in thyroid hormone levels cause large changes in TSH. Serum TSH is the most sensitive test for primary hypothyroidism.

Question 86

Function of alpha-adrenergic agonists

Answer 86

increase systolic and diastolic blood pressure by stimulating alpha1-adrenoreceptors in the vascular walls, causing vasoconstriction. The elevated systemic blood pressure then causes a reflexive increase in vagal tone,resulting in decreased heart rate and slowed atrioventricular node conduction

Question 87

Before birth, high pulmonary vascular resistance (PVR) and low systemic vascular resistance (SVR) facilitate right to left shunting through the ductus arteriosus, and both ventricles contribute to fetal systemic blood flow. At birth, what happens?

Answer 87

decreased PVR (due to oxygenation and ventilation of the lungs) and increased SVR (due to umbilical cord clamping) reverse shunting through the ductus arteriosus (ie, left to right shunting) and only the left ventricle contributes to systemic blood flow.

Question 88

What is myotonic dystrophy?

Answer 88

an autosomal dominant condition caused by a trinucleotide repeat expansion; successive generations typically have an increased number of repeats, resulting in early and more severe disease (ie, anticipation). In children, cognitive/behavioral issues may be the initial findings before development of muscle weakness and myotonia.

Question 89

What is the pathogenesis of mycobacterium tuberculosis?

Answer 89

primarily replicates within the phagosome, leading to display of mycobacterial antigens on major histocompatibility complex class II molecules. This results in the activation of CD4 cells and subsequent control of the infection with macrophages.

Question 90

The chest x-ray in acute decompensated heart failure typically shows?

Answer 90

prominent pulmonary vessels; patchy, bilateral airspace opacification; and blunting of the costophrenic angles due to pleural effusions.

Question 91

All patients beginning treatment with Tumor necrosis factor-alpha (TNF-alpha) inhibitors should be evaluated for?

Answer 91

Tumor necrosis factor-alpha (TNF-alpha) inhibitors impair cell-mediated immunity. All patients beginning treatment with Tumor necrosis factor-alpha (TNF-alpha) inhibitors should be evaluated for latent tuberculosis.

Question 92

What is the leading cause of acute exacerbations of chronic obstructive pulmonary disease?

Answer 92

Viral and bacterial respiratory infections. The most common bacterial pathogens include nontypeable Haemophilus influenzae, Streptococcus pneumoniae, and Moraxella catarrhalis.

Question 93

What is ataxia-telangiectasia?

Answer 93

an AR disorder resulting from defective DNA break repair. Classic findings include cerebellar ataxia, telangiectasias, and recurrent sinopulmonary infections.

Question 94

What is fibromyalgia?

Answer 94

most commonly in women age 20-55 and presents with diffuse musculoskeletal pain, fatigue, and neuropsychiatric disturbances. It is characterized by abnormal central processing of painful stimuli. Although initially painful, aerobic exercise helps to improve pain and functioning in these patients.

Question 95

Where is the vomiting reflex located?

Answer 95

initiated by the chemoreceptor trigger zone (ie, area postrema) and nucleus tractus solitarius within the dorsal medulla at the caudal end of the 4th ventricle. The area postrema does not have a well-developed blood brain barrier, allowing it to be activated directly by emetogenic substances (eg, drugs, toxins) or indirectly by ascending afferents from the bowel wall (eg, chemotherapy-induced release of serotonin)

Question 96

What is a common comorbid disorder with panic disorder?

Answer 96

Panic disorder consists of recurrent and unexpected panic attacks characterized by an abrupt surge of anxiety and distressing cardiopulmonary/neurologic symptoms. Agoraphobia, a common comorbid disorder, results in anxiety about and avoidance of situations where patients may feel trapped and helpless in the event of a panic attack (eg, crowds, enclosed spaces, public transportation)

Question 97

What is seen in a subfalcine herniation?

Answer 97

occurs when the cingulate gyrus is displaced under the falx cerebri. Subfalcine herniation may compress the ipsilateral anterior cerebral artery, resulting in ischemia and contralateral leg weakness.

Question 98

What is seen in stimulant intoxication?

Answer 98

Stimulant intoxication can present with paranoid ideation and must be differentiated from primary psychiatric disorders. Physical signs of stimulant intoxication include mydriasis, tachycardia, hypertension, and diaphoresis.

Question 99

MOA of methotrexate for ectopic pregnancy?

Answer 99

Ectopic pregnancy occurs due to pregnancy implantation in an extrauterine location (eg, fallopian tube). Medical treatment is with methotrexate, which inhibits DNA synthesis and cell reproduction, primarily in actively proliferating cells such as fetal cells and trophoblasts.