Uworld13 Flashcards
Function of aromatase and its deficiency
Aromatase is responsible for converting androgens into estrogens.
Deficiency of this enzyme causes accumulation of androgens during pregnancy, resulting in ambiguous external genitalia in newborn females and maternal gestational virilization
What is stranger anxiety?
Stranger anxiety, which presents as crying or screaming when unfamiliar people approach, is a normal and expected part of childhood development.
It typically begins around 6 months and resolves by 2 years.
What is thyroid hormone resistance?
Decreased sensitivity of peripheral tissues to thyroid hormones due to a defect in the thyroid hormone receptor.
Levels of thyroxine, triiodothyronine, and TSH are increased.
Patients classically have goiter and frequently develop attention deficit hyperactivity disorder.
What is lateral epicondylitis (tennis elbow)?
Overuse of wrist extensor muscles (extensor carpi radialis, extensor digitorum) leading to angiofibroblastic tendinitis at their attachment on the lateral epicondyle
Unlike Plasmodium falciparum, the eradication of Plasmodium vivax and Plasmodium ovale requires?
Requires primaquine to target the dormant hepatic phase.
Patients not receiving treatment that targets the hepatic phase will likely develop relapsed symptoms weeks or months later.
The work of breathing is minimized in patients with?
Increased elastic resistance (eg pulmonary fibrosis) when their respiratory rate is high and tidal volume is low (fast, shallow breaths)
What is the work of breathing in patients with diseases that increase airflow resistance (eg, asthma, chronic obstructive pulmonary disease)?
Breathe at a lower respiratory rate and higher tidal volume (slow, deep breathes) to minimize the work of breathing.
Treatment for bulimia nervosa?
Nutritional rehabilitation, cognitive-behavioral therapy, and pharmacotherapy with selective serotonin reuptake inhibitors. Fluoxetine is drug of choice.
What is ataxia-telangiectasia?
AR; results from a defect in DNA-repair genes.
The DNA of these patients is hypersensitive to ionizing radiation.
Manifestations include cerebellar ataxia, oculocutaneous telangiectasias, repeated sinopulmonary infections, and an increased incidence of malignancy.
What is the function of neprilysin?
Neprolysin is responsible for the breakdown of the natriuretic peptides and angiotensin II; therefore, inhibition of neprilysin increases the activity of these peptides.
For treatment of heart failure, neprilysin inhibition is combined with angiotensin II receptor blockade to optimize the positive effects of the natriuretic peptides (vasodilation, diuresis) while blocking the negative effects of angiotensin II (eg vasocontriction, fluid retention)
Pelvic fracture are frequently associated with injury to?
The posterior urethra, in particular the bulbomembranous junction.
Inability to void despite a full bladder sensation, a high riding boddy prostate, and blood at the urethral meatus are clinical findings suggestive of urethral injury.
How do penicillins and cephalosporins function?
By irreversibly binding to penicillin-binding proteins such as transpeptidases.
A change in the structure of penicillin-binding proteins that prevents cephalosporin binding is one mechanism of bacterial resistance to cephalosporins.
What are the potassium levels in diabetic ketoacidosis?
Most patients with diabetic ketoacidosis have normal to increased serum potassium levels despite a total body potassium deficit.
Replacement of potassium is a crucial step in the management of patients with diabetic ketoacidosis.
MOA of letrozole
Polycystic ovary syndrome can present with irregular menses, enlarged ovaries, and anovulatory infertility.
Letrozole, an aromatase inhibitor, acts on the ovary and peripheral adipose tissue to inhibit androgen-to-estrogen conversion by the enzyme aromatase; the subsequent decrease in estrogen production causes the pituitary to release more FSH and LH, thereby stimulating ovulation
Where do potassium sparing diuretics (spironolactone, amiloride) act on the nephron?
Act on the late distal tubule and cortical collecting duct to antagonize the effects of aldosterone
All diuretics except the potassium sparing class cause potassium loss by increasing sodium delivery to the late distal tubule and cortical collecting duct, where aldosterone-induced sodium reabsorption occurs at the expense of potassium.
What is the path of the phosphoinositol second messenger system?
The phosphoinositol second messenger system begins with ligand-receptor binding and Gq protein activation leading to activation of phospholipase C (PLC).
PLC then hydrolyzes phosphatidyl inositol bisphosphate and forms diacylglycerol and inositol triphosphate (IP3)
Finally, IP3 activated protein kinase C via an increase in intracellular Ca2+
Central nervous system lesions cause what to the face?
Because the upper face receives bilateral input from the motor cortices, central nervous system lesions typically cause lower facial weakness that spares the forehead on one side of the fact.
Peripheral lesions (Bell palsy) cause what to the face?
cause weakness of the entire side of the face. Bell palsy may also result in decreased tear production, hyperacusis, and reduced taste sensation.
How can SNRI be used for neuropathic pain?
Serotonin-norepinephrine reuptake inhibitors are often used for neuropathic pain. They increase norepinephrine in the central synapses, which modulates the descending pain pathway, leading to decreased central perception of pain.
What is primary ciliary dyskinesia?
results from an autosomal recessive mutation in the proteins responsible for normal flagellar and ciliary structure and function (eg, dynein, assembly proteins)
CF: situs inversus, chronic sinusitis, bronchiectasis, and infertility.
What is the most life threatening complication associated with Marfan syndrome?
Cardiovascular lesions.
Early onset cystic medial degeneration of the aorta predisposes to aortic dissection, the most common cause of death in these patients.
When should Turner syndrome be suspected?
Turner syndrome (loss of an X chromosome) should be suspected in a newborn girl with cystic hygroma or lymphedema.
Dysmorphic features (high arched palate, low set ears) and aortic anomalies (coarctation) are some findings.
What is a harmartoma?
Hamartomas are common, slow growing, benign lung neoplasms microscopically characterized by nodules of disorganized, mature connective tissue (cartilage, fat) and entrapped respiratory epithelium. They are often detected incidentally by imaging, appearing as well circumscribed, peripheral, solitary lung lesions.
Lymph from the testes drains?
Through lymph channels directly back to the para-aortic lymph nodes
Lymph from the scrotum drains?
to the superficial inguinal lymph nodes.
Selective estrogen receptor modulators (tamoxifen, raloxifene) MOA
Selective estrogen receptor modulators exhibit estrogen antagonist and agonist properties in a tissue specific manner.
Raloxifene has estrogen agonist activity on bone, which decreases bone resorption and improves bone density. It has an estrogen antagonist effect on breast tissue, decreasing the risk for break cancer; it also acts as an estrogen antagonist in the uterus and does not increase the risk for endometrial cancer.
Tamoxifen acts as an estrogen agonist in the uterus and increases the risk for endometrial hyperplasia and cancer.
How many calories is in protein/carbs and fat?
metabolism of 1 g of protein/carb = 4 calories of energy
metabolism of 1 g fat = 9 calories
MOA of benzodiazepines?
Act by binding to the benzodiazepine binding site, which allosterically modulates the binding of GABA, resulting in an increased frequency of chloride ion channel opening.
The influx of chloride ions into the neurons causes neuronal hyperpolarization and inhibition of the action potential.
What is dissociative amnesia?
An isolated inability to recall important autobiographical information that is inconsistent with ordinary forgetfulness. It typically occurs abruptly following an overwhelming, traumatic event.
Flexor digitorum profundus tendon insertion and function
Inserts onto the base of the distal phalanx and flexes the distal interphalangeal (DIP) joint.
It is susceptible to rupture when an actively flexed DIP joint is forcefully hyperextended
What is factor V Leiden mutatuon?
Inherited causes of hypercoagulability should be considered in patients younger than 50 who present with thrombosis and no obvious explanation for an acquired prothrombotic state.
The factor V Leiden mutation, which causes factor Va resistance to inactivation by activated protein C, may account for approximately 20% of cases of atypical venous thrombosis.
Treatment for enterobius vermicularis infection (enterobiasis)
enterobius vermicularis infection (enterobiasis) occurs most frequently in children and presents with perianal pruritus.
Diagnosis is made by indentifying eggs in the perianal region (cellulose tape test).
Treatment: albendazole, mebendaozle, and pyrantel pamoate.
What is anemia of chronic disease?
Is a consequence of chronically elevated inflammatory cytokines, most important hepcidin.
This peptide inactivates iron channels on enterocytes and reticuloendothelial macrophages, leading to reduced iron absorption and reduced iron release from the reticuloendothelial system.
The net result is normocytic or slightly microcytic anemia with low reticulocyte response, low serum iron level, or normal or low total iron binding capacity.
A stoke in the lateral brainstem can lead to?
Ipsilateral Horner syndrome because sympathetic neurons travel next to the spinothalamnic tract in the lateral medulla.
What is the cause of Down syndrome?
CF: cognitive impairment, facial dysmorphism, and cardiac defects
95% of cases are caused by the presence of an extra chromosome 21 (trisomy) resulting from nondisjunction.
Unbalanced Robertsonian translocations or mosaicism are less common causes.
Lepromin skin test results for patients in leprosy
The lepromin skin test will be positive in patients with tuberculoid leprosy as they exhibit a strong CD4+ Th1 cell mediated immune response to Mycobacterium leprae.
Patients with lepromatous leprosy will test negative due to their weak Th1 cell mediated immune response
Signs of vitamin A toxicity?
benign intracranial hypertension (headache, vomitting, papilledema), dry skin, and hepatomegaly.
Risk factors: excessive dietary intake (egg, liver, kidney) or retinoid containing meds
What is Trousseau syndrome? (migratory superficial thrombophlebitis)
A paraneoplastic syndrome of hypercoagulability may be seen in some patients with cancer, especially adenocarcinomas of the pancreas, colon or lung.
Superficial venous thromboses may therefore appear in one site and then resolve, only to recur in another site. This is known as Trousseau syndrome, an indication of visceral cancer.
What is gonadal dysgensis (streak ovaries)
Most commonly caused by Turner syndrome and results in primary ovarian insufficiency (amenorrhea, infertility)
Patients are at increased risk for aortic dissection and horseshow kidney
