Uworld11 Flashcards
vasopressin-2 receptor mutations are a cause of?
congenital nephrogenic diabetes insipidus, a condition in which renal resistance to antidiuretic hormone results in excessive urinary water losses.
findings: high baseline serum osmolality (typically with hypernatremia), persistently dilute urine after water deprivation (low urine osmolality) and lack of response to desmopressin.
Autism spectrum disorder is characterized by?
impaired social communication/interactions and restricted, repetitive interests or behaviors.
It can occur with or without language and intellectual impairment.
Defective anterior (rostral) neuropore closure (eg, anencephaly) results in?
failure of the skull and meninges to form, allowing exposure of the developing brain to the destructive effects of amniotic fluid.
Open neural tube defects are a result of defects in primary neuralation (development and closure of the neural tube).
Aside from cigarette smoke, what is the most important environmental risk factor for lung cancer?
Radon is a radioactive gas found throughout the earth that enters homes through contaminated soil and groundwater. It emits highly ionzing alpha radiation, causing DNA damage in the respiratory tract epithelium when inhaled.
Folate deficiency inhibits?
the synthesis of nucleic acids, particularly the formation of thymidine.
This leads to defective DNA synthesis and increased apoptosis affecting hemopoietic cells (megaloblastic anemia).
Thymidine supplementation bypasses the enzyme thmidylate synthase and can reduce erythroid cell apoptosis.
How can glycerol be be used to synthesize glucose during gluconeogenesis?
Glycerol produced by the degradation of triglycerides in adipose tissue can be used by glycerol kinase in the liver and kidney to synthesize glucose during gluconeogensis.
What is cholesteatomas?
collections of squamous cell debris that form a mass behind the tympanic membrane.
Can be congenital or may occur as an acquired primary lesion or following infecton, trauma, or surgery of the middle ear.
Can cause hearing loss due to erosion into auditory ossicles.
The histopathologic features of esophageal squamous cell carcinoma include?
solid nests of neoplastic squamous cells with abundant eosinophilic cytoplasm and distinct borders.
Areas of keratinization and the presence of intercellular bridges are also present.
Patients present with progressive solid and eventually liquid dysphasia and weight loss.
What is sick sinus syndrome>
Sick sinus syndrome results from degeneration (usually age related) of the sinoatrial node, leading to impaired conduction and reduced cardiac output with symptoms of dyspnea, fatigue, lightheadedness, presyncope, and syncope.
ECG: bradycardia with sinus pauses (delated P waves), sinus arrest (dropped P waves) and junctional escape beats
Calcium efflux from cardiac cells prior to relaxation is primarily mediated via?
Na/Ca exchange pump and sarcoplasmic reticulum Ca-ATPase pump
What is the most common cause of renal infarction?
Systemic thromboembolism, often due to thrombus formation during atrial fibrillation.
Renal infarction presents with flank pain, hematuria, elevated lactate dehydrogenase, and a wedge shaped kidney lesion on CT.
The brain and kidneys are more likely to suffer embolic infarctions because they are perfused at a higher rate.
The initial management of septic shock requires rapid fluid resuscitation to replace intravascular volume and restore adequate end-organ perfusion. This is best accomplished with?
intravenous boluses of isotonic crystalloid in the form of 0.9% (normal) saline or lactated Ringer solution because these solutions remain in the extracellular space.
What is Kartagener syndrome?
a form of primary ciliary dyskinesia characterized by the triad of situs inversus, chronic sinusitis, and bronchiectasis.
Occurs due to mutations that impair the structure or function of cilia
Scaphoid fracture increase the risk of?
Scaphoid fracture can disrupt retrograde blood supply to the proximal scaphoid, increasing risk of avascular necrosis.
Fracture of the scaphoid bone may result from a fall on an outstretched hand and should be suspected if exam shows tenderness in the anatomic snuff box.
Patients with Bell Palsy may experience?
Because of the diverse functions of the facial nerve CNVII, patients with Bell palsy may experience decreased tear production, hyperacusis, and/or loss of taste over the anterior 2/3 tongue, in addition to unilateral facial weakness.
How does phenytoin cause vitamin D def?
Phenytoin and other antiepileptic meds are inducers of cytochrome P450 enzymes, including CYP24, which converts 25-hydroxyvitamin D to 24,25-dihydroxyvitamin D (inactive from).
As a result, there is less 25-hydroxyvitamin D available for conversion to 1,25-dihydroxyvitamin D (Active form), leading to def
Parathyroid hormone is released in a combination continuous/tonic and pulsatile pattern. Continous high levels of PTH lead to?
excessive release of calcium from bones and increase risk of osteoporosis.
Parathyroid hormone is released in a combination continuous/tonic and pulsatile pattern. Pulsatile secretion leads to?
an anabolic effect on bone metabolism, stimulating osteoblast proliferation and inducing increased formation of new bone.
Atrial natriuretic peptide, brain natriuretic peptide, and nitric oxide activates?
guanylyl cyclase and increase conversion of guanosine 5’-triphosphate to cyclic guanosine 3’,5’-monophosphate (cGMP).
MOA of phosphodiesterase inhibitors (eg, sildenafil)
decrease the degradation of cGMP.
Elevated intracellular cGMP levels lead to relaxation of vascular smooth muscle and vasodilation.
What is pleiotropy?
pleiotropy describes instances where multiple phenotypic manifestations result from a single genetic mutation
Rheumatoid arthritis has what antibodies?
Rheumatoid arthritis: symmetric polyarthritis (involving the metacarpophalangeal and proximal interphalangeal joints) with prolonged morning stiffness and fatigue.
Antibodies to citrullinated peptides/proteins have a high specificity for the condition.
What is polycythemia vera?
a myeloproliferative disorder characterized by uncontrolled erythrocyte production.
Almost all patients have a mutation in the JAK2 gene, which encodes a non-receptor (cytoplasmic) tyrosine kinase a/w the erythropoietin receptor.
What makes the pulmonary vascular bed unique?
The pulmonary vascular bed is unique in that tissue hypoxia results in a vasoconstrictive response.
Such hypoxic vasoconstriction occurs in the small muscular pulmonary arteries to divert blood flow away from underventilated lung regions and toward well-ventilated lung areas to minimize ventilation-perfusion mismatch, leading to more efficient overall gas exchange.
Pathogenesis of chronic granulomatous disease
Defective intracellular killing of phagocytized organisms within neutrophils due to an impaired respiratory burst.
CGD should be suspected in a child with recurrent infections by catalase+ organisms (staph aureus, aspergillus) who has normal immunoglobins and no leukopenia.
Why can repeat infection of dengue be more severe?
There are 4 different serotypes of dengue virus. Repeat infection occurs when a person is exposed to a serotype not previously encountered. Secondary infections are often far more severe than primary infections and may be a/w a life threatening shock syndrome.
MOA of class IA antiarrythmics (quinidine, procainamide, disopyramide)
sodium channel blocking agents that depress phase 0 depolarization. They also prolong repolarization due to moderate potassium channel blocking activity, increasing action potential duration in cardiac myocytes
What is hereditary hemochromatosis?
AR disease characterized by excessive gastrointestinal absorption of iron, which is then stored as hemosiderin in various tissues.
Secondary arthritis is common and typically involves the second and third metacarpophalangeal joints.
Liver disease, skin hyperpigmentation, diabetes, pituitary hormone def (eg central hypogonadism) and cardiomyopathy can also manifest.
What is croup
croup is a viral infection in which edema and narrowing of the proximal trachea (subglottis) result in a barky cough and inspiratory stridor.
MOA of penicillins
penicillins, structurally similar to D-alanine-D-alanine, inhibit transpeptidase by binding covalently to its active site.
The result is failed synthesis of the bacterial peptidoglycan cell wall
What does the murmur of aortic stenosis sound like?
systolic ejection type, crescendo-decrescendo murmur that starts after the first heart sound and typically ends before the A2 component of the second heart sound.
The intensity of the murmur is proportional to the magnitude of the left ventricle to aorta pressure gradient during systole.
what is the formula of maintenance dose?
clearance (CL) determines the dose rate required to maintain a given steady-state plasma concentration (Css)
maintenance dose= Css x CL x dosing interval
What does helicobacter pylori produce?
Produces the enzyme urease, which spilts urea into CO2 and ammonia and neutralizes the local acidic gastric pH.
Active infection can be confirmed through rapid urease testing, in which a biopsy specimen of gastric mucosa is evaluated in the presence of urea and a pH indicator.
Evidence of alkalization (due to ammonia formation) confirms the diagnosis
What are some complications of hand foot and mouth disease?
hand foot and mouth disease (oral ulcerations and rash on palms/soles) is a common manifestation of enterovirus infection.
Although enterovirus are typically self-limited, rare but serious complications include myocarditis and aseptic meningitis.
Closure of a patent ductus arteriosus results in?
decreased pulmonary venous return to the left atrium (decreased left ventricular preload) and increased diastolic blood pressure in the aorta (increased left ventricular afterload).
Together, these changes acutely lower left ventricular stroke volume and cardiac output
What is the virulence factor for group B strep
GBS is a major cause of neonatal sepsis.
Virulence factor: polysaccharide capsule, which contains sialic acid residues that prevent phagocytosis via molecular mimicry
What is a complication of giant cell arteritis?
GCA: granulomatous inflammation of the media with fragmentation of the internal elastic lamina most often affecting the medium and small branches of the carotid artery
Ischemic optic neuropathy with irreversible blindness is a potential complication; therefore patients require immediate glucocorticoid therapy
function of osteocytes
Osteocytes detect increased mechanical load in the bones (eg, weight-bearing exercise) and communicate with one another through gap junctions to orchestrate bone remodeling.
What is adenovirus
self-limiting, year round infection that causes the acute onset of fever, cough, congestion, pharyngitis, and conjunctivitis.
This pharyngoconjunctival disease can occur in outbreaks among those living in close quarters (eg, camp dormitories, military barracks).
