UWorld_1.17

Question 1

Presentation of Fragile X

Answer 1

• more common/severe in males
• mild-moderate cognitive impairment, speech/language delay, ADHD, mild autism
• macroorchidism
• prominent jaw, long face, large ears, cleft palate
• mitral valve prolapse
• short height, joint laxity, scoliosis, pes cavus, double-jointed thumbs, single palmar crease

Question 2

Cause of Fragile X

Answer 2

• highest inherited cause of cognitive impairment
• increase in trinucleotide repeat in FMR1 gene on X chromosome

Question 3

Presentation of CNIII palsy

Answer 3

• unilateral headache
• eye pain
• dilated, unreactive pupil
• diplopia
• ptosis
• ipsilateral eye = “down and out”

Question 4

Cause of CNIII palsy

Answer 4

• CN III runs between posterior cerebral and superior cerebellar artery
• aneurysm @ either vessel ==> CNIII palsy

Question 5

Calculation of number needed to harm

Answer 5

• NNH = number of people that must be treated in order to harm 1 person
• NNH = 1/attributable risk
• attributable risk = adv.event rate_treatment - adv.event rate_placebo

Question 6

Isoproteronol MOA

Answer 6

• agonist at B₁ and B₂ receptors w/no alpha receptor activity ==>
  
  • increase in cardiac contractility (B₁)
  • vascular smooth muscle relaxation (B₂)

Question 7

Major process used to maintain blood glucose levels @ 18-24 hrs

Answer 7

• gluconeogenesis = glucose formed from lactate, glycerol, and amino acids

Question 8

Important steps in gluconeogenesis

Answer 8

1. pyruvate ==> oxaloacetate (pyruvate carboxylase) [@ mitochondria]
2. OAA ==> malate (malate dehydrogenase) [@ mitochondria]
3. malate ==> OAA ==> phosphoenolpyruvate (PEP carboxykinase = “PEPCK”) [@ cytosol]
4. PEP ==> glucose (fructose-1,6-bisphosphatase & glucose-6-phosphatase)

Question 9

unsteady gait + blanching nests of distended capillaries + pulmonary infections ==> dx? + mechanism

Answer 9

• Ataxia telangectasia
• [autosomal recessive] mutation @ ATM (“Ataxia telangectasia mutated”) gene = DNA break repair ==>
  
  • sensitive to xray radiation
  • cerebellar ataxia
  • telangectasias = blanching nests of distended cappilaries
  • predisposed to hematologic malignancies
• IgA deficiency ==> predisposition to respiratory infections

Question 10

Nerve coursing near piriform recess + fxn

Answer 10

• internal laryngeal nerve (branch of CN X) courses superficially through mucosa @ piriform recess
  
  • fxn = afferent cough reflex
  • can be damage by food objects caught in piriform recess or in efforts to retrieve them

Question 11

Factors ==> increased risk of renal calculi

Answer 11

• increased concentrations of:
  
  • calcuim
  • uric acid
  • oxalate
  • phosphate
• decreased water

Question 12

Factors ==> decreased risk of renal caculi

Answer 12

• increased water intake
• increased citrate ==> binds free Ca and prevents precipitation and facilitates excretion

Question 13

Rates of metabolism of various non-glucose sugars

Answer 13

• Fructose = fastest
  
  • phosphorylated @ liver ==> fructose-1-P ==> bypasses PFK-1 = rate-limiting step
• other sugars metabolized slower than fructose:
  
  • Galactose ==> glucose-6-P ==> glycolysis
  • Mannose ==> fructose-6-P ==> glycolysis

Question 14

Cresent formation @ kidney on light microscopy ==> dx?

Answer 14

rapidly progressive glomerulonephritis

Question 15

Mechanism of rapidly progressive glomerulonephritis

Answer 15

• RPG ==> formation of crescent formation + focal necrosis
• crescents = glomerular parietal cells, monocytes, macrophages, fibrin ==> sclerotic ==> irreversible renal injury

Question 16

Muscle contraction @ skeletal msucle vs. cardiac muscle

Answer 16

• skeletal muscle
  
  • AP ==> L-type-Ryr ==> Ca in T-tubule system (most of Ca from sarcoplasmic reticulum) ==> contraction
  • NO DEPENDENCE ON EXTRACELL Ca
• cardiac muscle
  
  • AP ==> opening L-type Ca channels ==> entry of Ca ==> contraction
  • DEPENDENT ON EXTRACELL Ca

Question 17

Vascular rxn to intimal/endothelial injury

Answer 17

• hyperplasia and fibrosis
• mostly mediated by medial smooth muscle cells
  
  • injured endothelial cells release platelet-derived growth factor ==> migration and proliferation of mSMCs
  • vascular cell-adhesion molecules (VCAMs) allow attachment of WBCs ==> release of cytokines ==> also attract mSMCs

Question 18

Embryonic origin of melanocytes = ?

Answer 18

neural crest cells

Question 19

intensly pruritic rash on flexor surfaces, worse at night, usually @ kids or those who work w/kids ==> dx? + mechanism

Answer 19

• Scabies = infestation of sarcoptes scabiei mite
• Type IV hypersensitivity rxn to mites and eggs
• erythematous papules + excoriations; rapidly spreading

Question 20

Characteristics of HepA infection

Answer 20

• commonly asymptomatic or subclinical (anicteric) in children; self-lmiting
• can also: N/V, jaundice, RUQ pain, malaise/fatigue, aversion to smoking
• usually uncommon but more severe @ adults

Question 21

Extent/fxn of mucous and cilia @ lungs

Answer 21

• cilia = trachea ==> respiratory bronchials
• mucous (goblet cells) = interspersed from trachea ==> larger bronchials (not present @ terminal bronchials)
• mucous + cilia ==> mucociliary clearance of foreign particles and organisms

Question 22

Common organisms + treatment of urethritis in young male

Answer 22

• organisms = N. gonorrheae or C. trachomatis
• N. gonorrhea tx = ceftriaxone
• C. trachomatis = doxycycline or azithromycin

Question 23

Tx of acute mania

Answer 23

• mood stabilizers = lithium, valproate, carbamazepime
• • atypical antipsychotic = olanzapine