First Aid 2013 Errata pdf free download - 2013 First Aid for the USMLE Step 1 Official Updates, Corrections, and Clarifications Last Revised: May 13th 2013


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2013 First Aid for the USMLE Step 1 Official Updates, Corrections, and Clarifications Last Revised: May 13th, 2013 Despite our best efforts, errors do occur during a revision. This update addresses content errors and typos that may create confusion. If you are the first to submit a referenced correction or suggestion to us at www.firstaidteam.com that we accept and integrate into the book, you will receive up to a $20 gift certificate. We check every submission against your reference or other authoritative references to ensure accuracy. Please note that our goal is to provide a high-yield framework for studying and not a comprehensive textbook. Good luck with your studies! –The First Aid/USMLE-Rx Team CATEGORIES OF UPDATES Corrections  Factual errors that interfere with comprehension Minor Corrections  Less significant errors that may cause confusion Suggestions & Clarifications  The text is accurate, but could be written more clearly  Minor formatting issues (misalignments, indents, etc.)  Helpful additions that improve the quality of a fact NOTE: Entries with bolded/underlined page number are the newest additions to the official errata (also includes older entries that have been recently updated or reclassified). CORRECTIONS Page Fact Name Correction 72 tRNA In the figure depicting tRNA charging, methionine should not be included on the left image. Amino acids such as methionine are covalently bound to the 3’ end of the tRNA by aminoacyl-tRNA synthetases. 102 Electron transport chain and oxidative phosphorylation The arrow beneath “Complex V” should be facing upwards (to reflect movement of protons through the complex), not downward. 118 Bacterial structures The chemical composition of the plasma membrane is best described as a phospholipid bilayer, not a lipoprotein bilayer. 135 E. Coli In the entry for EIEC, in the second column, delete “No toxins produced.” 136 Salmonella vs. Shigella Under the column for Shigella, note that antibiotic therapy shortens the duration of organism excretion (shedding) in the stool. 162 Hepatitis viruses For the hepatitis D virus (HDV) entry, in the incubation column, note that co-infection represents an acute infection of both HBV and HDV and superinfection represents infection with HDV after developing chronic HBV. 221 Tumor suppressor genes BRAF is a proto-oncogene, not a tumor suppressor gene. 231 G-protein–linked 2nd messengers For the Gq-coupled receptor pathway, note that the role of phospholipase C is not to cleave lipids into PIP2, but rather to cleave PIP2 into both DAG and IP3 (one step downstream). 255 Cardiac and vascular function curves For the graph, note that an acute, uncompensated hemorrhage would only result in a left shift of the volume curve; cardiac function is unchanged. See the new position of bullet point #3 below. 288 Insulin (1) In the entry for regulation, note that growth hormone (GH) increases insulin resistance, leading indirectly to increased insulin secretion. It does not directly stimulate insulin release. (2) Under the list of insulin regulators, note that β2-agonists, not antagonists, increase insulin secretion. (3) In the image of a pancreatic β cell, note that glucose enters the cell via GLUT-2, not GLUT-1. 322 Pancreatic secretions In the entry for trypsinogen, replace “creation of more trypsinogen” with “cleaving of other trypsinogen molecules into active trypsin.” 350 Pathologic RBC forms In the entry for acanthocytes (spur cells), the image shown is actually an echinocyte (burr cell). Acanthocytes have irregularly spaced, longer projections (see image below) as compared to burr cells, whose projections are smaller and more uniformly spaced. Image: Zamel, R et al. Abetalipoproteinemia: two case reports and literature review. Orphanet Journal of Rare Diseases 2008, 3:19. doi:10.1186/1750-1172-3-19 351 Other RBC pathologies Under the entry for Heinz bodies, note that the mechanism for Heinz body formation is oxidation of hemoglobin sulfhydryl groups leading to denatured hemoglobin precipitation, not iron oxidation from the ferrous to the ferric form as we currently state. 361 Reed-Sternberg cells It is the lymphocyte-rich variant of Hodgkin’s lymphoma that has the best long-term prognosis, not the nodular sclerosing form. 427 Spinal cord and associated tracts The lateral spinothalamic tract label should be posterior and lateral to the anterior spinothalamic tract, as opposed to indicating the dorsal horn. 475 Tricyclic antidepressants Desipramine has a lower (not higher) seizure threshold than the other TCAs. 525 Hydatidiform mole For complete hydatidiform moles, the most common genetic makeup is an enucleated egg fertilized by a single sperm that subsequently duplicates the paternal DNA; an egg being fertilized by two distinct sperm is rare. MINOR CORRECTIONS Page Fact Name Correction 64 Chromatin structure For the Histone methylation entry, please replace “Inactivates transcription of DNA” with “Can activate or repress transcription in a context-specific manner.” For the DNA methylation entry, please add “DNA methylation at CpG islands represses transcription” and move the mnemonic “Methylation makes DNA mute” to the DNA methylation row. 68 DNA replication In the table entry for DNA ligase, please replace “phosphodiesterase” with “phosphodiester.” 77 Collagen For the type III entry, replace the phrase in column 3 as follows: Type III: defective in Ehlers-Danlos syndrome, vascular type. 78 Osteogenesis imperfecta Please note that in the most common type of OI (type I), the mutation leads to decreased production of otherwise normal type I collagen. 88 Autosomal trisomies In the entry for Down syndrome, the last sentence of the third column should read, “Ultrasound shows ↑nuchal translucency in first trimester.” 113 Fatty acid metabolism Replace the label “Inner mitochondrial membrane” with “Mitochondrial membranes.” 121 Obligate anaerobes Actinomyces israelii is better classified as a facultative anaerobe, not an obligate one. 148 Protozoa – CNS infections In the entry for transmission of Toxoplasma gondii, replace the first part of the first sentence with: “Cysts in meat or oocysts in cat feces.” 193 205 Sinusoids of spleen Infections in immunodeficiency For these two facts, add E. coli to the list of encapsulated organs and change the mnemonic to “ShiNE SkiS” (the E is for E. coli). 207 Immune deficiencies (cont.) Wiskott-Aldrich syndrome is due to a defect in the WASP gene, not the WAS gene. 251 Interatrial septum development In the text for step 5, note that the septum secundum, not the foramen secundum, enlarges. 294 Signaling pathways of endocrine hormones To clarify, the IP3 pathway plays a minor role in GHRH signaling. The principal signaling pathway for GHRH is cAMP accumulation. 335 Budd-Chiari syndrome Budd-Chiari syndrome is associated with hypercoagulable states (plural). 366 Langerhans cell histiocytosis Delete “(neural crest origin)” from the second-to-last sentence of the second paragraph. Langerhans cells are of mesodermal origin, despite expressing the marker S-100. 406 Gout drugs Please note that colchicine is primarily used clinically to treat acute gout rather than chronic gout. 494 Wilms’ tumor (nephroblastoma) It is the WT2 gene (not WT1) that has a stronger association with Beckwith-Wiedemann syndrome. 505 Embryologic derivatives The urethra is derived mostly from endoderm, not mesoderm. 521 Menstrual cycle The arrow indicating when ovulation occurs should appear slightly after the LH surge, rather than before the LH surge. 576 Rapid review The treatment for Sporothrix schenckii should be oral potassium iodide, not potassium chloride. SUGGESTIONS & CLARIFICATIONS Page Fact Name Suggestion/Clarification 60 Grief In the entry for the onset of pathologic grief, replace “prolonged grief lasting > 2–6 months” with “prolonged grief lasting > 1 year” to make it consistent with the duration of normal bereavement (pathologic grief is normal bereavement that does not resolve within 1 year). 65 De novo pyrimidine and purine synthesis This fact states that “Various antineoplastic and antibiotic drugs function by interfering with purine synthesis.” Please note that some of the drugs listed interfere with purine synthesis, while others interfere with pyrimidine synthesis. 78 Ehlers-Danlos syndrome Delete the sentence “Type I or Type V collagen most frequently affected in severe classic Ehlers-Danlos syndrome” as this information goes beyond the scope of the Step I. Instead, replace it with the following high-yield clinical pearl: “May be confused with Marfan syndrome which is due to a defect in fibrillin, not collagen.” 79 Alport syndrome Replace “Most common form is X-linked recessive” with “Most common form is X-linked; males are more severely affected than female carriers.” 82 Genetic terms In the entry for Imprinting, please change the word “mutation” to “allele.” 83 Imprinting (1) For Prader-Willi syndrome, change “Paternal allele is not expressed” to “Paternal (active) allele is deleted.” (2) For Angelman syndrome, change “Maternal allele is not expressed” to “Maternal (active) allele is deleted.” 91 Vitamin B3 (niacin) The synthesis of vitamin B3 (niacin) requires both vitamin B6 (pyridoxine) and vitamin B2 (riboflavin). 98 Summary of pathways For the vitamin B12-dependent succinyl-CoA synthesis pathway, replace “Odd-chain fatty acids and branched-chain amino acids” with “Odd-chain fatty acids and the amino acids valine, isoleucine, methionine, and threonine.” 100 Glycolysis regulation, key enzymes Under the box for glycolysis steps requiring ATP, replace “*Glucokinase in liver; hexokinase in all other tissues.” With “*Glucokinase in liver and β cells of pancreas; hexokinase in all other tissues.” 101 TCA cycle (Krebs cycle) The calculation of 10 ATP produced per acetyl-CoA via the TCA cycle is based on 2.5 ATP per NADH, 1.5 ATP per FADH2, and 1 ATP per GTP. 102 Electron transport chain and oxidative phosphorylation In the entry for ATP produced via ATP synthase, replace “1 NADH  3 ATP; 1 FADH2  2 ATP.” With “1 NADH  2.5 ATP; 1 FADH2  1.5 ATP.” 105 Sorbitol Note that levels of sorbitol dehydrogenase in the lens of the eye, while present, are much lower than in the other tissue types listed. 108 Catecholamine synthesis/tyrosine catabolism For the box labeled “Breakdown products via MAO and COMT,” update the contents as follows: Dopamine  HVA Norepinephrine  Normetanephrine  VMA Epinephrine  Metanephrine  VMA 121 Obligate aerobes Pseudomonas aeruginosa may use some nitrogen-containing compounds (e.g., nitrates) as terminal electron acceptors for anaerobic metabolism in environments with low or absent oxygen. 154 Viral envelopes Since picornavirus is an RNA virus and parvovirus is a DNA virus, the mnemonic makes more sense if the order of picornavirus and parvovirus is switched in the second column. 215 Leukocyte extravasation In the entry for migration, under the second column, replace “bacterial products” with “products released in response to bacteria.” 238 β-blockers Under the entry for MIs as an application of β-blockers, note that the specific agents shown to reduce mortality (per the COMET trial) are metoprolol, carvedilol, and bisoprolol. 258 Auscultation of the heart Please refer to the updated heart murmurs chart shown below: 259 Heart murmurs (1) For the description of the aortic stenosis murmur, replace “Radiates to carotids/heart base” with “Loudest at heart base; radiates to carotids.” (2) In the entry for mitral valve prolapse, please replace the sentence “Loudest at S2” with “Loudest just before S2.” (3) In the entry for mitral valve prolapse, please replace “Enhanced by maneuvers…” with “Occurs earlier with maneuvers…” 267 Patent ductus arteriosus Please note that there are two key pathologic stages. In the neonatal period, lung resistance ↓ and the shunt becomes left to right. Untreated, the shunt may lead to RVH, LVH, and rarely heart failure. Uncorrected PDA with chronic overload of the pulmonary vasculature can eventually result in pulmonary hypertension and shunt reversal (Eisenmenger syndrome), manifesting as cyanosis and clubbing in the lower extremities (differential cyanosis). 281 Lipid-lowering agents In the table entry for ezetimibe, please replace “reabsorption” with “absorption.” 291 Adrenal steroids In the figure, please note that the primary source of both testosterone and DHT is not the zona reticularis. For testosterone, it is the testes; for DHT, it is peripheral tissues. 298 Hypothyroidism vs. hyperthyroidism Myxedema (facial/periorbital) is correctly mentioned as associated with hypothyroidism. Note, however, that periorbital edema is also associated with hyperthyroidism. 301 SIADH Note that hyponatremia in SIADH is secondary to increased water reabsorption; hypoaldosteronism is a compensatory response to maintain volume status which has the undesired effect of increased Na+ excretion. 302 Diabetes mellitus (1) In the entry for acute manifestations, in the second column, please add “can be caused by” before the “unopposed secretion of GH” (diabetes does not cause unopposed secretion of GH). (2) In the entry for chronic manifestations, in the second paragraph, please replace “(sorbitol accumulation in organs with aldose reductase)” with “(sorbitol accumulation in organs with aldose reductase and low or absent sorbitol dehydrogenase).” (3) In the entry for chronic manifestations, in the first bullet point, replace “arteriosclerosis leading to hypertension” with “arteriolosclerosis leading to hypertension,” which better reflects the small vessel nature of the disease process. 304 Multiple endocrine neoplasias (MEN) Please note that MEN 2A is associated with parathyroid hyperplasia, not parathyroid adenomas. 326 Celiac sprue Replace “↓ mucosal absorption that primarily affects jejunum” with “↓ mucosal absorption that primarily affects distal duodenum and/or proximal jejunum.” 336 Hereditary hyperbilirubinemias In the entry for Gilbert’s syndrome, in the second column, replace the first sentence with the following: “Mildly ↓ UDP-glucuronyl transferase conjugation activity leading to ↓ bilirubin uptake by hepatocytes.” 352 Microcytic, hypochromic (MCV < 80 fL) anemia (1) In the entry for α-thalassemia, first sentence of second column, replace “α-globin gene mutations” with “α-globin gene deletions” to better reflect the genetic defect. (2) In the third column, replace all instances of “gene” with “allele.” 357 Extrinsic hemolytic normocytic anemia (1) For the indirect Coombs’ test, to trigger the reaction, anti-IgG antibodies (Coombs’ reagent) must be added after the RBCs are added to the patient’s serum. (2) For the direct Coombs’ test, note that anti-Ig antibodies are added to the patient’s blood, not serum. 360 Hereditary thrombosis syndromes leading to hypercoagulability For antithrombin deficiency, please replace “↑ in PTT is blunted after heparin administration” with “PTT normalizes after heparin administration.” 366 Chronic myeloproliferative disorders In the entry for chronic myeloproliferative disorders, please replace “constitutively active JAK2 receptors” with “constitutively active JAK-STAT signaling pathway” (JAK2 is a non-receptor tyrosine kinase). 371 Antimetabolites In the “Azathioprine, 6-mercaptopurine (6-MP), 6-thioguanine (6-TG)” entry, for toxicities, note that only 6-MP toxicity increases with allopurinol administration (6-TG is broken down by an alternative deamination mechanism and its metabolism is not affected by allopurinol). 373 Microtubule inhibitors In the entry for vincristine and vinblastine, the mechanism of action affects both the S phase and the M phase of the cell cycle. 382 Upper extremity nerves For the radial nerve and median nerve territories, “(C5–T1)” and “(C5–C8, T1)” mean the same thing. 418 Homunculus In the homunculus image, we do not show the sensory distribution of the abdomen and genitalia. 422 Effects of strokes With a PICA (lateral medullary) stroke, there is ipsilateral loss of facial pain/temperature sensation and contralateral loss of body pain/temperature sensation. 425 Ischemic brain disease/stroke The definition of a transient ischemic attack is an episode of focal neurological dysfunction lasting < 24 hours. The majority of attacks resolve prior to 1 hour. 437 Facial lesions In the diagram, remove the arrows associated with the green lines that point toward the cerebral cortex; CN VII is predominantly efferent. 438 Common eye conditions Accommodation is not an eye condition, but rather a normal physiological function to focus on near objects. 439 Extraocular muscles and nerves Patients with a CN IV palsy will tilt their head in the contralateral direction as a compensatory mechanism. Tilting the head in the ipsilateral direction worsens the vertical eye deviation, as stated in the book. 446 Neurocutaneous disorders Sturge-Weber syndrome can be associated with either hemiparesis or hemiplegia. 502 ACE inhibitors In the third column, angiotensin II receptor blockers have a reduced (rather than absent) risk of cough/angioedema. 515 Female reproductive epithelial histology Note that the stratified squamous epithelium of the ectocervix is also nonkeratinized. 517 Seminiferous tubules To clarify, in the line drawing, the size of primary spermatocytes is generally equal to that of spermatogonia, not smaller. 528 Cervical pathology Replace the third sentence of the second column with the following: “Associated with HPV 16 and HPV 18, which produce both the E6 gene product (inhibits p53 suppressor gene) and E7 gene product (inhibits RB suppressor gene).” 545 Diaphragm structures In the third column, the spelling of “esophagus” should be changed to “oesophagus” to make the mnemonic for “10 letters at T10” valid. 563 Asthma drugs In the entry for methylxanthines, replace “thereby ↓ cAMP hydrolysis” with “thereby resulting in ↑ cAMP levels due to ↓ cAMP hydrolysis.”

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