NBME Explanations

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NBME Explanations

NBME 19 questions and answers

Discussion in 'USMLE Step 1' started by conan, Mar 20, 2017.

  1. conan

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    If thats what you got for correct answer i will change. Thank you. You would think since lymph node were dissected. N would be considered as well.
     
  2. jeremiah dore

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    I put rocky mountain and got it wrong so I am assuming they want Lyme disease??
     
  3. notoch0rd

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    I answered with Lyme Disease and it was correct.
     
  4. notoch0rd

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    I was wandering if someone can elaborate on the answers to the following questions.


    9) 48 yo woman fatigue, weakness, loss of appetite, and weight loss. Serum PTH increased. Xray of skeletal system shows generalized osteopenia with subperiosteal resorption of bone within the phalanges. MOA?

    PTH mediated production of transforming growth factor beta 1?



    47) 40yo woman chorionic villus sampling. Chromosome analysis shows 46XY in 14 cells and 47, XY+15 in 25 cells. Chromosome analysis of amniotic fluid shows 46XY in 50 cells. Dx?

    confined placental mosaicism



    50) 2 wk old full term female newborn develops pale stools and progressive jaundice. Nuclear scans show no excretion of bile. A1AT deficiency ruled out. Liver biopsy shows inflammation and proliferation of small bile ducts and increased portal fibrosis. If not treated, what develops?

    Budd-Chiara syndrome



    26) Study function of voltage-gated sodium channel. A mutant form that inactivates more rapidly than normal is developed. Whats effected?

    Increase the conduction velocity of axon?



    3) Niemann-Pick diease pathophysiologic process?

    Increased synthesis of glycosphingolipids?

    (that’s what I chose as well but it was wrong. Was “decreased lysosomal hydrolase activity” the correct answer then?”



    34) 65 yo man radical prostatectomy and lymph node dissection for adenocarcinoma of prostate. Grading?

    Metastatic spread

    (I chose Metastatic spread as well, but it was wrong. My next choice would be lymph node involvement?)




    44) 53 yo woman w/ GERD. Dietary change and stress reduction no effect symptoms. Physical exam shows mild epigastric tenderness. Tx?

    Omeprazole

    (My initial instinct was to look for a sucralfate as a knee jerk reaction to ‘protection’ but then chose Misoprostol. Wouldn’t Misoprostol provide protection by increasing the production and secretion of the mucous barrier?)



    35) 66 yo man inability to maintain erection. Fatigue and difficulty sleeping and concentrating. Cerebral infract 3 months ago with right hemiparesis that gradually improved. Physical exam normal. What other findings?

    Lidido, Nocturnal erections: normal

    (Was the cerebral infarction just a distractor?)



    31) 5 yo boy pain in right eye at night. No Fx of neoplasia. Exam shows strabismus and tenderness in eye. Left eye normal. Retina show presence of mass. Physician explain unlikely to develop other neoplasms. Mutation occurs?

    Retinal cells



    27) cDNA clone of ovalbumin contains 1872 bp. Genomic clone contains 7700 bp. why?

    Introns

    (I almost always get these kinds of questions wrong… Wiki elaborates on the subject of cDNA by stating that - The number of introns present in a cDNA is zero, since it is derived from eukaryotic mRNA which does not contain introns (polycistronic))



    35) 41 yo woman at 34wk gestation has amniocentesis due to uncontrolled HTN. Amnionic fluid shows decreased lecithin:sphingomyelin of 1.5:1 (N=3:1). What condition to newborn born at this time?

    Decreased FRC



    24) 40yo man increased malaise, nausea, abdominal pain and light colored stools. Tenderness to RUQ. Bilirubin:4, ALP: 180, AST: 1500, ALT: 1700. HBeAg, HBsAg, HBV-DNA, IgM anti-HBc antigen: positive. Further observation shows CD8 T cells bind to antigens resulting in liver injury. Where’s antigen from?

    Hepatocytes.



    25) 52 yo man severe headache, anxiety, sweating and palpitations. Well controlled HTN w/ clonidine and HCTZ, but ran out of Rx 3 days ago. P120, BP170/110, Physical exam diaphoresis. What happens after injection of propranolol?

    Increase total peripheral resistance and decrease cardiac output?


    Thanks!
     
  5. A-Cor

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    Propanolol is b1/b2 noselect block so, dont think CO will increase. This also indicates that it decreased
    https://www.ncbi.nlm.nih.gov/pubmed/8237812
    A is wrong, I picked it so, must be B
     
  6. A-Cor

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  7. notoch0rd

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    I believe the answer to
    "3) 13yo girl grew 3in over summer. What accounts for increased Ca absorption?"
    was - "increased Ca absorption due to 7 dehydrocholesterol" , as that's what I answered and it didn't appear in my incorrects. My approach to this was: summer months->increased exposure to the sun->increased vit.D->increased Ca absorption.
     
  8. A-Cor

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  9. A-Cor

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    Sorry misread the answers D would be correct.
     
  10. A-Cor

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    Can anyone tell me what D is then?
     
  11. A-Cor

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    Budd-Chiari is wrong I picked it. Dont think it is cirrhosis since, a1 is ruled out and that leads to it. Seems like hepatitis cells are inflamed.Probably got it from mom.
     
  12. conan

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    The qustion stem was too vague anyway. usually for Lyme disease they would put targetoid lesion as well. just rash, joint pain, flu like symptoms can be anything, without using geographic location as indication for most common disease.
     
  13. conan

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    #33 conan, Mar 27, 2017
    Last edited: Mar 27, 2017
    chorionic villus only sample the placental. but amniotic fluid actually sample fetus DNA. thats why although placental shows 2 types of cell. but amniotic fluid shows one type, the fetus is still normal. And its mosaic b/c there's 2 types of cell in placenta
     
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  14. conan

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    LOL. yes cerebral infarction was a distractor. since he doesn't have any physical nerve damages down there. his nocturnal erections should be normal. ANd remember our (men) libido never decreases...LOL. but our refractory time does increase...ah..the sadness of being old...can't wait.
     
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  15. conan

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    The diagnosis is not hepititis. Its Congenital biliary atresia i think. so if portal vein fibrosed you would get budd chiari syndrome.
     
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  16. conan

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    PPI is always 1st line for GERD
     
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  17. conan

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    #37 conan, Mar 27, 2017
    Last edited: Mar 27, 2017
    there's distinction between congenital and acquired. If its congenital then yes he has both the Rb gene turned off then he will have more cancer. And you know the boy doesn't have congenital Retinoblastoma (Rb) because no one in family has Rb. So this is just random acquired mutation, its only limited to the retinal cells not germ cells.
     
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  18. conan

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    #38 conan, Mar 27, 2017
    Last edited: Mar 27, 2017
    Pt has acute HBV infection. high AST and ALT means hepatocytes are lysing. once hypatocytes are infected w/ HBV it places HBV on surface and signals cytotoxic Ts to kill them.
     
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  19. conan

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    the baby has trouble producing surfactant thats why lecithin:sphingomyelin ratio low (below normal). so lungs cannot inflate fully. as a result baby functional residual capacity would be low as well.
     
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  20. conan

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    ok. cDNA means complementary DNA which is DNA produced from processed RNA. genomic DNA has full base pair: 7700. After transcription and all the introns spliced out the final RNA would only have 1872bp and be ready for translation. So a cDNA produced from a processed RNA would be shorter b/c all the introns are cut out.
     
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