Uworld26

Question 1

What is seen on physical examination of pneumothorax?

Answer 1

Pneumothorax is recognized on chest x-ray by a continuous line without lung markings peripheral to it.

Decreased tactile fremitus, decreased breath sound intensity, and hyperresonance to percussion are expected on physical examination.

Question 2

Severe hypoxemia that does not correct with 100% supplemental oxygen is consistent with?

Answer 2

right to left shunt.

Intrapulmonary shunt effect occurs when an alveolar filling process (eg, diffuse pulmonary edema) causes poor alveolar ventilation despite continued perfusion; this improves with positive end-expiratory pressure.

Question 3

What is vibrio vulnificus?

Answer 3

curve, gram-negative, free living bacterium that grows in marine environments.

Transmission primarily occurs due to the consumption of raw seafood (eg, oysters) or wound contamination.

Manifestations are often mild, but individuals with liver disease or iron overload are at very high risk of severe, fulminant infection (eg, sepsis, necrotizing fascitis)

Question 4

What is Huntington disease?

Answer 4

AD, progressive neurodengerative disorder characterized by chorea, psychiatric symptoms, and dementia.

Psychiatric symptoms may occur early in the disease course and include irritability, anxiety, apathy, depression, and psychosis.

Question 5

Adverse effects of amphotericin B

Answer 5

Amphotericin B is a polyene antifungal drug notorious for its renal toxicity.
Severe hypokalemia and hypomagnesemia are commonly seen during therapy and often require daily supplementation.

Question 6

What is a delayed hemolytic transfusion reaction?

Answer 6

Delayed hemolytic transfusion reactions are usually mild, hemolytic reactions that occur >24 hours after blood transfusion.

They are a type of anamnestic response (delayed immunologic response) that occurs in patients previously exposed to a minor RBC antigen (eg, previous blood transfusion, pregnancy)

Question 7

What is prepatellar bursitis?

Answer 7

A bursa is a fluid-filled synovial sac that serves to alleviate pressure from bony prominences and reduce friction between muscles and tendons.

Acute trauma or chronic repetitive pressure can cause injury, leading to localized pain and tenderness.

Prepatellar bursitis causes anterior knee pain and is usually due to repetitive or prolonged kneeling.

Question 8

What is a chancroid due to Haemophilus ducreyi?

Answer 8

Chancroid, due to Haemophilus ducreyi, presents as deep, painful ulcers with ragged borders that are associated with a grey exudate and inguinal lymphadenopathy.

Diagnosis is established by gram stain and culture of the organism from a scraping of the ulcer base.

Question 9

What is acute urinary retention?

Answer 9

characterized by anuria and bladder distension and can result in hydronephrosis and acute kidney injury.

A palpable, distended bladder is present on examination, and abdominal and flank pain may be present.

The most common cause of urinary retention is bladder outlet obstruction (urethral compression) due to benign prostatic hyperplasia.

Question 10

Radiation-induced lung injury typically occurs following?

Answer 10

Radiation-induced lung injury typically occurs following thoracic irradiation (eg, breast cancer), which damages pneumocytes and vascular endothelial cells and initiates an inflammatory response (eg, IL-1, TNFa, TGF-b).

This immune response can have both acute (eg, exudative alveolitis, hyaline membrane formation) and delayed (eg, dense fibrosis) effects that typically manifest with cough and dyspnea.

Question 11

Nonpitting edema often develops due to?

Answer 11

lymphatic outflow obstruction (eg, malignancy, congenital malformation).

Congenital lymphedema due to lymphatic network dysgenesis is common in Turner syndrome, which is characterized by webbed neck, horseshoe kidney, and nail dysplasia.

Question 12

What is the locus coeruleus?

Answer 12

The locus coeruleus is a paired brainstem nucleus located in the posterior rostral pons near the lateral floor of the fourth ventricle and functions as the principal site for norepinephrine synthesis in the brain.

It projects to virtually all parts of the central nervous system and helps control mood, arousal (reticular activating system), sleep wake states, cognition, and autonomic function.

Question 13

Staph epidermidis is a common cause of foreign body infections due to?

Answer 13

its ability to produce adherent biofilms.

Question 14

What is MEN1?

Answer 14

Multiple endocrine neoplasia type 1 syndrome is characterized by tumors of the pituitary, parathyroid gland, and pancreas.

Question 15

First generation H1 histamine receptor antagonists, including diphenhydramine and chlorpheniramine, can cause significant?

Answer 15

sedation especially when used with other meds that cause CNS depression (such as benzodiazepines)

Question 16

What is epithelial ovarian cancer?

Answer 16

the most common ovarian malignancy.

Histo findings include anaplasia of epithelial cells with invasion into the stroma and multiple papillary formations with cellular atypia.

Epithelial ovarian tumors are associated with elevated cancer antigen 125, which can be used as a serum marker for this condition.

Question 17

What is a Aschoff body?

Answer 17

Interstitial myocardial granulomas (Aschoff bodies) are found in carditis due to acute rheumatic fever, which develops after an untreated group A strep pharyngeal infection.

Aschoff bodies contain plump macrophages with abundant cytoplasm and central, slender ribbons of chromatin (Anitschkow, or caterpillar, cells)

Question 18

What is frontotemporal dementia?

Answer 18

presents with early personality change, executive dysfunction, compulsivity, and hyperorality.

It is associated with neurofibrillary tangles due to abnormal tau proteins (also seen in Alzheimer dementia) and pathologically ubiquinated TDP-43 (also seen in amyotrophic lateral sclerosis)

Question 19

What is Kallman syndrome?

Answer 19

In Kallman syndrome, there is an absence of GnRH secretory neurons in the hypothalamus due to defective migration from the olfactory placode.

These patients have central hypogonadism and anosmia, and often present with delayed puberty.

Question 20

What is unique about Mycoplasma?

Answer 20

All organisms in the Mycoplasma genus, including Ureaplasma urealyticum, lack peptidoglycan cell walls and are therefore resistant to agents that target the cell wall such as penicillins, cephalosporins, carbapenems, and vancomycin.

Mycoplasma infections can be treated with antiribosomal agents (eg, tetracyclines, macrolides)

Question 21

What is seen in diabetes with the polyol pathway?

Answer 21

In hyperglucemic states, aldose reductase converts glucose to sorbitol at a rate faster than sorbitol can be metabolized.

Sorbitol accumulates in certain cells such as lens cells, causing an influx of water and resulting in osmotic cellular injury.

Depletion of NADPH by aldose reductase also increases oxidative stress, which accelerates development of cataracts and diabetic microvascular complications (eg, neuropathy, retinopathy )

Question 22

What is a manic episode?

Answer 22

Manic episodes are characterized by euphoric/irritable mood, impulsivity, hyperactivity, decreased need for sleep, pressured speech, racing thoughts, and grandiosity. They may occur with or without psychotic features.

Question 23

MOA of aspirin

Answer 23

Aspirin is a nonsteroidal anti-inflammatory drug that primarily and irreversibly inhibits cyclooxygenase-1 (COX-1) when given in low doses.

Because irreversible COX-1 inhibition decreases platelet thromboxane A2 production for the duration of their lifespan (ie, 3-7 days), preoperative aspirin discontinuation is recommended at least 5 days prior to surgery to avoid excessive bleeding.

Question 24

Activation of muscarinic receptors by acetylcholine or cholinergic agonists results in?

Answer 24

peripheral vasodilation due to synthesis of nitric oxide in endothelial cells, which leads to vascular smooth muscle relaxation (eg, hypotension).

Muscarinic receptor activation in other sites causes smooth muscle contraction.

Question 25

What is prevalence?

Answer 25

the actual number of existing cases (old and new) of disease, either at a particular point in time (point prevalence), or during a period of time (period prevalence). Estimates of disease prevalence in a population are affected by population dynamics.

Question 26

Diffusion speed across a semipermeable membrane increases with?

Answer 26

higher molecular concentration gradients, larger membrane surface areas, and increased solubility of the diffusing substance. Diffusion speed decreases with increased membrane thickness, smaller pore size, higher molecular weights, and lower temps.

Question 27

How does mitochondrial dysfunction present?

Answer 27

presents with myopathy, nervous system dysfunction, lactic acidosis, and ragged red fibers on muscle biopsy. Mitochondrial myopathies due to mtDNA mutations are inherited solely in a maternal fashion (ie, maternal inheritance). Therefore, transmission occurs only through affected females and never through males.

Question 28

Function of the iliohypogastric nerve

Answer 28

provides sensation to the suprapubic and gluteal regions and motor function to the anterolateral abdominal wall muscles. Abdominal surgery (eg, appendectomy) can damage the nerve and cause decreased sensation and/or burning pain at the suprapubic region.

Question 29

What are central scotomas?

Answer 29

A scotoma is a discrete visual field defect. Central scotomas are often caused by age-related macular degeneration that leads to the deposition of drusen clustered around the macula.

Question 30

What is sensitivity?

Answer 30

represents the probability that an individual with disease with have a positive test result.

Question 31

What is specificity?

Answer 31

represents the probability that an individual without disease will have a negative test result.

Question 32

Drugs that have been shown to improve long term survival in patients with heart failure with reduced ejection fraction include?

Answer 32

beta blockers, ACE inhibitors, angiotensin II receptor blockers, angiotensin receptor-neprilysin inhibitors, and aldosterone antgaonists.

Question 33

What causes rigor mortis?

Answer 33

Muscle contraction involves continuous actin-myosin cross-bridge cycling driven by release of sarcoplasmic calcium stores. After death, loss of ATP prevents both myosin head detachment and clearance of cytoplasmic calcium, leading to diffuse and persistent skeletal muscle stiffening (rigor mortis)

Question 34

How does cocaine effect the heart?

Answer 34

Cocaine intoxication causes increased sympathetic activity, which may be recognized by agitation, dilated pupils, tachycardia, and hypertension. Cocaine-induced chest pain typically results from myocardial oxygen supply-demand mismatch (ie, myocardial ischemia) in the setting of coronary artery vasoconstriction. Sublingual nitroglycerin and benzodiazepines help improve the myocardial ischemia and relieve the chest pain.

Question 35

Opiate analgesics reduce pain by?

Answer 35

binding to mu receptors and inhibiting synaptic activity in the central nervous system. Activation of presynaptic mu receptors on the primary afferent neuron leads to closure of voltage-gated calcium channels and reduced excitatory neurotransmitter release. Binding to mu receptors on the postsynaptic membrane causes opening of potassium channels and membrane hyperpolarization.

Question 36

What is the pathophysiology of benign neonatal hyperbilirubemia?

Answer 36

increased bilirubin production and decreased bilirubin conjugation as well as increased enterohepatic circulation. Indirect hyperbilirubinemia and jaundice typically peak in the first few days of life and usually resolve without intervention.

Question 37

What is neurofibromatosis type 1 (von Recklinghausen disease)?

Answer 37

AD disorder caused by mutations in the NF1 tumor suppressor gene. Patients characteristically develop numerous cutaneous neurofibromas comprised mostly of Schwann cells, which are derived from the neural crest.

Question 38

What is primary hyperaldosteronism?

Answer 38

involves excess aldosterone secretion, which causes hypertension and predisposes to hypokalemia and metabolic alkalosis; low plasma renin activity helps distinguish it from other causes of excess aldosterone (eg, renovascular disease). First line-medical therapy: mineralocorticoid receptor antagonist (eg, spironolactone, eplerenone)

Question 39

Foodborne botulism is caused by?

Answer 39

the ingestion of food contaminated with botulinum toxin, often from improperly home-canned foods. It leads to eye and bulbar symptoms with symmetric descending muscle weakness; fever and mental status changes are typically absent.

Question 40

What is first line pharmacotherapy for schizophernia?

Answer 40

Antipsychotic meds; MOA= D2 receptor antagonism

Question 41

What can be given to a patient with hemophilia to help with clotting?

Answer 41

Bleeding after a tooth extraction and history of hemarthrosis are suggestive of hemophilia. Decreased levels of factor VIII or IX lead to failure to convert prothrombin into thrombin and deficient thrombus formation. The addition of thrombin to the blood of a patient with hemophilia results in clotting.

Question 42

What is seen in kidney stones caused by hyperparathyroidism?

Answer 42

Most kidney stones are made of calcium salts and are idiopathic, but conditions that increase renal calcium excretion can increase the risk of stones. Hyperparathyroidism is a common cause of recurrent kidney stones and is typically associated with mild hypercalcemia and hypophosphatemia.

Question 43

What is osteosarcoma?

Answer 43

the most common primary malignant bone tumor in children and young adults and typically arises near the metaphyses of long bones (eg, femur, tibia), causing progressive pain and soft tissue swelling. Xray: lytic and sclerotic bone lesion Histopath: malignant tumor cells that produce neoplastic osteoid and mineralized bone

Question 44

What can cause polyhydramnios?

Answer 44

Polyhydramnios (excessive accumulation of amniotic fluid) presents with increased abdominal circumference out of proportion to gestational age. The etiology is decreased fetal swallowing or increased fetal urination. Fetal anomalies associated with impaired swallowing include gastrointestinal obstruction (eg, duodenal, esophageal, or intestinal atresia) and anencephaly.

Question 45

What is chronic pancreatitis?

Answer 45

often presents with epigastric pain and pancreatic exocrine insufficiency resulting in fat malabsorption/steatorrhea. On abdominal CT scan, the pancreas can be identified by its head in close assoication with the second part of the duodenum; its body overlying the aorta, left kidney, and renal vessels; and its tail lying within the splenorenal ligament.

Question 46

What is Sporothrix schenckii?

Answer 46

a dimorphic fungus that exists as yeasts at body temp. It is found in decaying plant matter and soul and is usually transmitted via cutaneous or subcutaneous inoculation while a person is farming, gardening, or landscaping. The major manifestation is a slowly progressive nonpurulent, nonpainful, nodular lymphagitis that progresses proximally along the lymphatic chain.

Question 47

What is the rate limiting step of de novo fatty acid synthesis?

Answer 47

Cytosolic acetyl-CoA carboxylase converts acetyl-CoA to malonyl-CoA during the rate limiting step of de novo fatty acid synthesis. Malonyl-CoA also inhibits the action of mitochondrial carnitine acyltransferase, thereby inhibiting beta oxidation of newly formed fatty acids.

Question 48

What is positive predictive value?

Answer 48

answers the question: if the test result is positive, what is the probability that a patient has the disease? PPV= true positives/ (TP + FP)

Question 49

Difference between EBV and CMV mononucleosis?

Answer 49

The monospot test is positive in most cases of the Epstein Barr virus associated mononucleosis. In immunocompetent patients with a heterophile antibody-negative mononucleosis-like syndrome, the most likely diagnosis is the cytomegalovirus infection.

Question 50

What is diffuse esophageal spasm?

Answer 50

periodic, simultaneous, and non-peristaltic contractions of the esophagus due to impaired inhibitory innervation within the esophageal myenteric plexus. Patients typically present with liquid/solid dysphagia and chest pain due to inefficient propulsion of food into the stomach.

Question 51

What is horseshoe kidney?

Answer 51

During embryologic development, fusion of the kidneys at their lower poles (horseshoe kidney) may prevent ascent if the kidneys from the pelvis. Although most patients remain asymptomatic, they are at increased risk for ureteropelvic junction obstruction, recurrent infection and nephrolithiasis. Can be caught on inferior mesenteric artery.

Question 52

What is membranous nephropathy?

Answer 52

a common cause of nephrotic syndrome in adults and can occur in association with solid malignancy, viral hepatitis, and SLE. Immune complex deposition in the subepithelial portion of the glomerular capillary wall causes diffuse thickening of the glomerular basement membrane (without increased cellularity); these glomeruli have a "spike and dome" appearance when stained with a silver stain.

Question 53

What is thoracic outlet syndrome?

Answer 53

most often caused by compression of the brachial plexus as it passes through the scalene triangle, the space bordered by the anterior and middle scalene muscles and the first rib. Symptoms typically include upper extremity numbness, tingling, and weakness that worsen with repetitive overhead arm movements. The presence of an anomalous cervical rib is risk factor for TOS.

Question 54

Which drug can increase the risk of osteoporosis?

Answer 54

Osteoporosis is a common cause of fragility fractures, which occur in the absence of significant trauma. Chronic or recurrent use of glucocorticoids (eg, prednisone) promotes osteoporosis and increased the risk of fractures.

Question 55

What are brown pigment gallstones?

Answer 55

are composed of calcium salts of unconjugated bilirubin and arise secondary to bacterial or helminthic infection of the biliary tract. Beta-glucuronidase released by injured hepatocytes and bacteria hydrolyzes bilirubin glucuronides to unconjugated bilirubin. The liver fluke Clonorchis sinensis has a high prevalence in East Asian countries and is a common cause of pigment stones

Question 56

What happens when you reduce the significance level alpha in a study?

Answer 56

allows researchers to report any significant findings with greater confidence.

Question 57

ACE inhibitors and angiotensin II receptor blockers are both what?

Answer 57

teratogens. Both decrease angiotensin II activity, leading to abnormal fetal renal development, oligohydramnios, and potential neonatal Potter sequence (ie, pulmonary hypoplasia, limb deformity)

Question 58

What is naloxone?

Answer 58

a pure opioid receptor antagonist used to treat opioid intoxication or overdose. Although it binds to mu, kappa and delta opioid receptors, it has the greatest affinity for mu receptors (which mediate opioid induced bradycardia and respiratory depression), making it an ideal agent for treating opioid intoxication.

Question 59

Activation of adrenergic receptors results in?

Answer 59

arrestin binding and receptor internalization. This effect is responsible for the tolerance effect seen with alpha-adrenergic (eg, decongestants, vasopressors) and beta-adrenergic (eg, bronchodilators) agonists.

Question 60

What is acute otitis media?

Answer 60

presents with an erythematous, bulging tympanic membrane and can be complicated by inflammation or infection of nearby structures. Spread of infection to the facial nerve (CN VII), which travels through the middle ear, can result in facial neuritis with unilateral facial paralysis.

Question 61

What is a subarachnoid hemorrhage?

Answer 61

presents with a generalized, excruciating headache. "worst headache of my life" Usually occurs due to rupture of saccular (berry) aneurysms or arteriovenous malformations. Berry aneurysms of the circle of Willis are associated with autosomal dominant polycystic kidney disease.

Question 62

Function of DNA polymerase I

Answer 62

In prokaryotes, only DNA polymerase I has both 5' to 3' and 3' to 5' exonuclease activities. The 3' to 5' exonuclease activity allows for a proofreading function during DNA replication, while the 5' to 3' exonuclease activity is involved in removal of RNA primers and repair of damaged DNA sequences.

Question 63

What is the pathogenesis of tuberculosis?

Answer 63

Mycobacterium tuberculosis triggers CD4 T lymphocytes to release interferon-gamma, which leads to macrophage activation (improves intracellular killing ability) and differentiation into epithelioid histiocytes. These cells, along with horseshoe-shaped, multinucleated Langhans giant cells (fused, activated macrophages) are a key component of granuloma formation.

Question 64

How does respiratory acidosis present?

Answer 64

low pH and high PaCO2. HCO3 initially remains near normal but becomes elevated over several days as renal compensation develops.

Question 65

Bronchodilation is most commonly accomplished with?

Answer 65

Bronchodilators induce bronchial smooth muscle relaxation to relieve airway spasm and bronchoconstriction in patients with asthma. Bronchodilation is most commonly accomplished with beta-2 receptor agonists (eg, albuterol), which function by increasing cyclic AMP levels in bronchial smooth muscle.

Question 66

What is poststreptococcal glomerulonephritis?

Answer 66

presents most commonly in children with hematuria, hypertension, and periorbital edema. Red blood cell casts and mild proteinuria may be present on urinalysis, and serum creatinine may be elevated.

Question 67

What is posttransplantation lymphoproliferative disorder?

Answer 67

occurs in patients who have undergone solid organ or stem cell transplantation and are taking high dose immunosuppressive medications. Most cases are caused by the reactivation of Epstein Barr virus, which generates viral proteins that stimulate B cell proliferation and survival. Patients usually have mononucleosis-like symptoms.

Question 68

Histopath exam of syphilitic lesions classically demonstrates?

Answer 68

proliferative endarteritis with a surrounding plasma cell infiltrate. Most of the manifestations of syphilis are due to localized tissue ischemia resulting from endarteritis.

Question 69

The acid-fast stain identifies organisms that have?

Answer 69

mycolic acid present in their cell walls, including Mycobacterium and some Nocardia species. Acid fast staining is carried out by applying an aniline dye (eg, carbolfuchsin) to a smear and then decolorizing with acid alcohol to reveal whether the organisms present are "acid fast".

Question 70

Patients who undergo cytotoxic chemotherapy are at high risk for?

Answer 70

bacterial infections due to neutropenia. Neutropenic fever often manifests with fever, chills, and hypotension but purulence is rare due to a lack of neutrophils.

Question 71

Vasopressin and desmopressin causes?

Answer 71

a V2 receptor-mediated increase in water and urea permeability at the inner medullary collecting duct. The resulting rise in urea reabsorption (decreased urea clearance) enhances the medullary osmotic gradient, allowing the production of maximally concentrated urine.

Question 72

What is the cardiac action potential conduction speed from fastest to slowest?

Answer 72

slowest in the atrioventricular node and fastest in the Purkinje system. Conduction speed of the atrial muscle is faster than that of the ventricular muscle. Purkinje system - Atrial muscle - Ventricular muscle - AV node

Question 73

What happens in anaphylaxis?

Answer 73

In anaphylaxis, allergen exposure triggers widespread IgE mediated release of inflammatory chemical mediators (eg, histamine, prostaglandin, leukotrienes). These chemical mediators cause peripheral vasodilation and increase vascular permeability, leading to hypotension.

Question 74

What is a Reed sternberg cell?

Answer 74

Reed-Sternberg cells are large binucleated cells with an owl's eyes appearance that appear on a background of lymphocytic infiltrates. Reed-Sternberg cells must be present histopathologically in order to make the diagnosis of Hodgkin lymphoma.

Question 75

What is aplastic anemia?

Answer 75

a form of bone marrow failure due to destruction of multipotent hematopoietic stem cells. It is marked by pancytopenia and profound hypocelluarity of the bone marrow with an abundance of fat cells and stroma. Impaired reticulocytosis and an absence of splenomegaly are important features.

Question 76

What is the difference between low and high doses of dopamine?

Answer 76

Low dose dopamine infusion stimulates D1 receptors in the renal and mesenteric vasculature, resulting in vasodilation and increased blood flow to these sites. Increasing doses of dopamine stimulate B1 and a1 receptors, resulting in increased cardiac output and elevated systemic vascular resistance. At the high end of the dose range, the increase in afterload can result in decreased cardiac output.

Question 77

What is the most common mechanism of sudden cardiac death due to acute myocardial infarction?

Answer 77

Ventricular fibrillation; it results from arrhythmogenic foci triggered by electrical instability in the ischemic myocardium

Question 78

What is seen in allergic bronchopulmonary aspergillosis?

Answer 78

Allergic bronchopulmonary aspergillosis due to Aspergillus fumigatus may complicate asthma. ABPA can result in transient recurrent pulmonary infiltrates and eventual proximal bronchiectasis.

Question 79

What day can you detect b-hCG in serum and urine?

Answer 79

b-hCG is produced by the syncytiotrophoblast after implantation, which generally occurs 6-7 days after fertilization at the earliest. b-hCG typically is detectable in the maternal serum 8 days after fertilization, whereas it is detectable in the urine 14 days after fertilization.

Question 80

What is seen in a 22q11.2 microdeletion syndromes?

Answer 80

22q11.2 microdeletion syndromes (eg, DiGeorge syndrome) may present with thymic hypoplasia (eg, thymic shadow attenuation). Because the thymus is required for T-cell maturation, reservoirs that receive migrating mature T cells (eg, paracortex of lymph nodes) will be poorly developed. In contrast, x linked agammaglobulinemia halts B-cell maturation in the bone marrow, preventing migration to lymph node cortical follicles.

Question 81

Direct oral anticoagulants such as rivaroxaban are often preferred over vitamin K antagonists such as warfarin in the treatment of conditions that require anticoagulation due to?

Answer 81

less variability in therapeutic drug effect; in contrast to vitamin K antagonists, the efficacy of direct oral anticoagulants is unaffected by dietary changes and most meds. Therefore, patients given direct oral anticoagulants do not require lab monitoring.

Question 82

What is the inheritance pattern of androgenetic alopecia?

Answer 82

Androgenetic alopecia is the most common cause of hair loss in both males and females. The pattern and severity of the baldness depend on both hormonal (circulating androgens) and genetic factors and vary between males and females. The condition is polygenic with variable expressivity.

Question 83

What is resistant to outliers?

Answer 83

An outlier is defined as an extreme and unusual observed vale in a dataset. It can affect measures of central tendency (mean, median, mode) as well as measures of dispersion (standard deviation, variance). Modes tend to be resistant to outliers.

Question 84

Function of thyroid perioxidase

Answer 84

TPO catalyzes the oxidation of iodine to iodine, the iodination of thyroglobulin tyrosine residues, and the iodotyrosine coupling reaction that forms T3 and T4. Antibodies against TPO are present in >90% of patients with chronic lymphocytic thyroiditis (Hashimoto)

Question 85

Chlamydia trachomatis serotypes L1 to L3 causes?

Answer 85

lymphogranuloma venereum, a sexually transmitted disease characterized initially by painless ulcers with later progression to painful inguinal lymphadenopathy ("buboes") and ulceration. Chlamydial inclusion bodies are seen in host cell cytoplasm.

Question 86

What is dyssynergic defecation?

Answer 86

Dyssynergic defecation occurs when the puborectalis muscle or the internal or external anal sphincter fails to relax during defecation, leading to chronic constipation. Dyssynergic defecation is usually considered a functional disorder and occurs more commonly in the elderly but may also occur with certain neurologic disorders (eg, Parkinson disease, multiple sclerosis) or trauma.

Question 87

What are the age related changes to the respiratory system?

Answer 87

decreased chest wall compliance and decreased alveolar elastic recoil with resulting alveolar enlargement and air trapping. These changes limit the potential increase in tidal volume and also increase the alveolar-arterial O2 gradient (ie, decrease the efficiency of alveolar-capillary gas exchange), reducing the ability to compensate for hypoxemia.

Question 88

What is seen in cardiac amyloidosis?

Answer 88

Cardiac amyloidosis, caused by the accumulation of misfolded amyloid fibrils, appears as pink, amorphous extracellular material on light microscopy. The ventricular walls become stiff and uniformly thickened, leading to impaired diastolic relaxation, a dilated left atrial cavity, and progressive left and right sided heart failure. Left ventricular cavity size is typically normal or decreased.

Question 89

What is rhabdomyolysis?

Answer 89

the release of intracellular muscle contents (eg, myoglobin, electrolytes) due to myocyte injury; it is common with crush injuries, seizures, or drug use (eg, statins). Heme pigment (released from myoglobin after degradation in the kidney) is toxic to tubular cells and can cause acute tubular necrosis. Positive blood on urine dipstick in the absence of RBCs on microscopic urinalysis suggests myoglobinuria.

Question 90

Function of transketolase

Answer 90

The pentose phosphate pathway consists of an oxidative (irreversible) branch and a nonoxidative (reversible) branch, and each can function independently based on cellular requirements. Transketolase, an enzyme of the nonoxidative branch, is responsible in part for the interconversion of ribose-5-phosphate (nucleotide precursor) and fructose-6-phosphate (glycolytic intermediate).

Question 91

What is adjustment disorder?

Answer 91

emotional or behavioral symptoms occurring within 3 months of an identifiable stressor. The diagnosis is indicated when the patient has significant distress and impairment but does not meet full criteria for another mental disorder.

Question 92

How can tumors acquire resistance to multiple chemotherapeutic agents?

Answer 92

by increasing expression of P-glycoprotein, a transmembrane ATP-dependent efflux pump that has broad specificity.

Question 93

What are the values of residual volume, forced vital capacity, and total lung capacity with aging?

Answer 93

Aging is associated with steady decreases in chest wall compliance but increases in lung compliance due to a loss of elastic recoil. Results in marked increase residual volume, decreased in forced vital capacity, and unchanged total lung capacity.

Question 94

What does the Valsalva maneuver do?

Answer 94

increases vagal tone and can be used to abolish paroxysmal supraventricular tachycardia. The rectus abdominis is the most important muscle in achieving the increased intraabdominal and intrathoracic pressure of the Valsalva maneuver.

Question 95

Main modes of transmission of hep B virus

Answer 95

sexual (among both heterosexual partners and men who have sex with men) and percutaneous (eg, intravenous drug use, needlestick accidents, blood transfusions). The risk of sexual transmission of hep C virus is low.

Question 96

Acute opioid overdose is characterized by?

Answer 96

altered level of consciousness, pinpoint pupils, and central respiratory depression. Patients are expected to have acute respiratory acidosis (low pH, high PaCO2) due to hypoventilation. Serum bicarbonate is typically near normal as there is not time for metabolic compensation in the acute setting.

Question 97

What happens when a drug is administered rectally?

Answer 97

Drugs administered orally must pass through the portal circulation and are subject to first pass metabolism by intestinal and hepatic enzymes. Rectal administration is capable of partially bypassing first pass metabolism due to the portion of venous outflow that goes directly to the systemic circulation; drugs with extensive first pass metabolism have increased bioavailability when administered rectally.

Question 98

What is the difference between vitamin B12 and folic acid deficiencies?

Answer 98

Vitamin B12 and folic acid deficiencies cause similar hematological pictures. However, neurological dysfunction is only seen in patients with vitamin B12 def. If megaloblastic anemia due to vitamin B12 deficiency is mistakenly treated with folate alone, the neurologic dysfunction can worsen.

Question 99

What is seen in carnitine deficiency?

Answer 99

Carnitine def impairs fatty acid transport from the cytoplasm into mitochondria, preventing beta-oxidation of fatty acids into acetyl CoA. This leads to cardiac and skeletal myocyte injury (lack of ATP from citric acid cycle) and impaired ketone body production by the liver during fasting periods.

Question 100

Type 1 HSR are mediated by?

Answer 100

the interaction of allergen with preexisting IgE bound to basophils and mast cells. This facilitates cross-linking of the surface IgE molecules that signals the cell to degranulate releasing chemical mediators (eg, histamine, heparin). These agents are responsible for the immediate signs and symptoms of allergy, from a local wheal and flare to life-threatening anaphylaxis