USMLE Step 2 CK Lecture Notes 2021: Pediatrics (2020)

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USMLE®Step 2 CKLecture Notes2021Pediatricsmedbookvn.com

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USMLE® is a joint program of the Federation of State Medical Boards (FSMB) and the NationalBoard of Medical Examiners (NBME), which neither sponsor nor endorse this product.This publication is designed to provide accurate information in regard to the subject matter coveredas of its publication date, with the understanding that knowledge and best practice constantly evolve.The publisher is not engaged in rendering medical, legal, accounting, or other professional service.If medical or legal advice or other expert assistance is required, the services of a competent profes-sional should be sought. This publication is not intended for use in clinical practice or the deliveryof medical care. To the fullest extent of the law, neither the publisher nor the editors assume anyliability for any injury and/or damage to persons or property arising out of or related to any use ofthe material contained in this book.© 2020 by Kaplan, Inc.Published by Kaplan Medical, a division of Kaplan, Inc.750 Third AvenueNew York, NY 10017All rights reserved. The text of this publication, or any part thereof, may not be reproduced in anymanner whatsoever without written permission from the publisher.10 9 8 7 6 5 4 3 2 1Course ISBN: 978-1-5062-6147-8Course Kit ISBN: 978-1-5062-6135-5Retail ISBN: 978-1-5062-6145-4Retail Kit ISBN: 978-1-5062-6137-9Kititemscome as a set and should not be broken out and sold separately.Kaplan Publishing print books are available at special quantity discounts to use for salespromotions, employee premiums, or educational purposes. For more information or to purchasebooks, please call the Simon & Schuster special sales department at 866-506-1949.

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EditorsWilliam G. Cvetnic, MD, MBAFellow of the American Academy of PediatricsBoard Certified in Pediatrics and Neonatal-Perinatal MedicineJacksonville, FloridaEduardo Pino, MDAssociate Professor, Department of PediatricsMarshall University School of MedicineMedical Director, Hoops Family Children’s HospitalCabell Huntington HospitalHuntington, West Virginia

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We want to hear what you think. What do you like or not like about the Notes?Please email us atmedfeedback@kaplan.com.

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Chapter Title00vTable of ContentsChapter 1:The Newborn1Chapter 2:Genetics/Dysmorphology21Chapter 3:Growth and Nutrition31Chapter 4:Development43Chapter 5:Behavioral/Psychological Disorders49Chapter 6:Immunizations53Chapter 7:Child Abuse and Neglect61Chapter 8:Respiratory Disease67Chapter 9:Allergy and Asthma81Chapter 10:Immune-Mediated Disease91Chapter 11:Disorders of the Eye99Chapter 12:Disorders of the Ear,Nose,andThroat105Chapter 13:Cardiology113Chapter 14:Gastrointestinal Disease139Chapter 15:Renal and Urologic Disorders155Chapter 16:Endocrine Disorders167Chapter 17:Orthopedic Disorders179

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viUSMLE Step 2 CKlPediatricsChapter 18:Rheumatic andVasculitic Disorders187Chapter 19:Hematology197Chapter 20:Oncology213Chapter 21:Neurology219Chapter 22:Infectious Disease237Chapter 23:Adolescence261Index267Additional resources available atkaptest.com/usmlebookresources

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Chapter Title001Learning Objectives❏Calculate an Apgar score❏Use knowledge of birth injuries to predict symptomology❏Demonstrate understanding of newborn screening, fetal growth/maturity, andneonatal infectionsAPGAR SCOREA newborn infant at birth is noted to have acrocyanosis, heart rate 140/min, andgrimaces to stimulation. She is active and has a lusty cry. What is her Apgar score?Table 1-1. Apgar Scoring SystemEvaluation0 Points1 Point2 PointsHeart rate0<100/min>100/minRespirationNoneIrregular, shallow, gaspsCryingColorBluePale, blue extremitiesPinkToneNoneWeak, passiveActiveReflex irritabilityNoneFacial grimaceActive withdrawalApgar scores are routinely assessed at 1 and 5 minutes, and every 5 minutes thereafter as longas resuscitation is continuing.•The1-minute scoregives an idea of what was going on during labor and delivery.•The5-minute scoregives an idea of response to therapy (resuscitation).In general, the Apgar score isnotpredictive of outcome; however, infants with score 0−3 at≥5minutes compared to infants with score 7−10 have a worse neurologic outcome.The Newborn1

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2USMLE Step 2 CKlPediatricsNewborn Care•Vitamin K IM•Prophylactic eye erythromycin•Umbilical cord care•Hearing test•Newborn screening testsBIRTH INJURIESOn physical exam, a 12-hour-old newborn is noted to have nontender swellingof the head that does not cross the suture line. What is the most likely diagnosis?Table 1-2. Common Injuries During DeliveriesInjurySpecificsOutcomeSkull fracturesIn utero from pressure against bones orforceps;linear:most common•Linear: no symptoms and no treatment needed•Depressed:elevate to prevent cortical injuryBrachial palsyErb-Duchenne:C5–C6; cannot abductshoulder; externally rotate and supinateforearm;Klumpke:C7–C8±T1; paralyzedhand±Horner syndromeMost with full recovery (months); depends onwhether nerve was injured or lacerated; Rx: properpositioning and partial immobilization; massageand range of motion exercises; if no recovery in3–6 mo, then neuroplastyClavicular fractureEspecially with shoulder dystocia in vertexposition and arm extension in breechPalpable callus within a week; Rx: withimmobilization of arm and shoulderFacial nerve palsyEntire side of face with forehead; forcepsdelivery or in utero pressure over facial nerveImprovement over weeks (as long as fibers werenot torn); need eye care; neuroplasty if noimprovement (torn fibers)Caput succedaneumDiffuse edematous swelling of soft tissues ofscalp;crosses suture linesDisappears in first few days; may lead to moldingfor weeksCephalohematomaSubperiosteal hemorrhage:does not crosssuture linesMay have underlying linear fracture; resolve in 2 wkto 3 mo; may calcify; jaundice

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Chapter 1lThe Newborn3PHYSICAL EXAMINATIONA newborn infant has a blue-gray pigmented lesion on the sacral area. It is clearlydemarcated and does not fade into the surrounding skin. What is the most likely diagnosis?A newborn has a flat, salmon-colored lesion on the glabella, which becomes darker redwhen he cries. What is the best course of management?Table 1-3. Physical Examination—Common FindingsFinding/DiagnosisDescription/CommentsSkinCutis marmorataLacy, reticulated vascular pattern over most of body when baby is cooled; improves over firstmonth; abnormal if persistsSalmon patch(nevus simplex)Pale, pink vascular macules; found in nuchal area, glabella, eyelids; usually disappearsMongolian spotsBlue to slate-gray macules; seen on presacral, back, posterior thighs; > in nonwhite infants;arrested melanocytes; usually fade over first few years;differential: child abuseErythema toxicum,neonatorumFirm, yellow-white papules/pustules with erythematous base; peaks on second day of life; containeosinophils; benignHemangiomaSuperficial: bright red, protuberant, sharply demarcated; most often appear in first 2 months;most on face, scalp, back, anterior chest; rapid expansion, then stationary, then involution (mostby 5–9 years of age); Rx: beta blockers, embolization;deeper: bluish hue, firm, cystic, less likelytoregress; Rx: (steroids, pulsed laser) only if large and interfering with functionHeadPreauriculartags/pitsLook for hearing loss and genitourinary anomalies.Coloboma of irisCleft of lid, iris, lens, retina, or choroid. In iris, manifests as keyhole appearance at the 6 o’clockposition. May be autosomal-dominant or part of CHARGE syndrome.Leukocoria—whitereflexRetinoblastoma; cataract; retinopathy of prematurity; retinal detachment; larval granulomatosisAniridiaHypoplasia of iris; defect may go through to retina; association with Wilms tumorextremitieSPolydactylyExtra digit, partial digit, or cleft digit after the 4th finger (ulnar side); world’s most common minormalformation; usually surgically removed at 1–2 years of agemedbookvn.com

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4USMLE Step 2 CKlPediatricsNEWBORN SCREENINGA 1-month-old fair-haired, fair-skinned baby presents with projectile vomiting of4days’ duration. Physical exam reveals a baby with eczema and a musty odor.Which screening test would most likely be abnormal?As per the American College of Medical Genetics, every newborn is screened for a corepanel of 29 disorders, with an additional 25 recommended (Expanded Newborn ScreeningProgram; varies per state).•All states now use tandem mass spectrometry; typically done after 24–48 hrs offeedings prior to baby leaving the birth hospital•With early discharge, may be performed at first postnatal visit (3–5 days) forimproved accuracy•In addition to a heel stick blood sample, current program also includes a hearingtest and pulse oximetry for critical congenital heart disease.Examples of the more common disorders in the expanded program include:•Phenylketonuria, tyrosinemia type I, 21-hydroxylase deficiency, classicgalactosemia•HbS/β-thal, Hb SS, HbS/HbC•Congenital hypothyroidism•Cystic fibrosisTable 1-4. Two Newborn Screening Diseases*Phenylketonuria (PKU)Classic GalactosemiaDefectPhenylalanine hydroxylase;accumulation of PHE in bodyfluids and central nervous systemGal-1-P uridylyltransferase deficiency;accumulation of gal-1-P with injury tokidney, liver, and brainPresentationIntellectual disabilityvomiting,growth retardation, purposelessmovements, athetosis, seizuresJaundice (often direct),hepatomegaly,vomiting,hypoglycemia,cataracts,seizures, poor feeding, poor weightgain,intellectual disabilityAssociationsFair hair, fair skin, blue eyes,tooth abnormalities,microcephalyPredisposition toE. colisepsis;developmental delay, speechdisorders, learning disabilitiesOthercommentsNormal at birth; gradual MR overfirst few monthsMay begin prenatally—transplacentalgalactose from motherTreatmentLow PHE diet for lifeNo lactose—reverses growth failure,kidney and liver abnormalities andcataracts,but notneurodevelopmental problemsG-1-P, galactose-1-phosphate; PHE, phenylalanine*Items inboldhave a greater likelihood of appearing on the exam.

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Chapter 1lThe Newborn5Hearing LossPediatric hearing loss is more prevalent than diabetes mellitus and all childhood cancers. Auniversal newborn hearing screening is recommended prior to newborn discharge, with thegoal of evaluating all hearing loss by age 3 months. Usually the otoacoustic emissions test (OAE)is used, where a small earphone/microphone is placed in the ear and sounds are played.•If hearing is normal, an echo is reflected back into the ear canal and is measuredby the microphone.•If hearing is not normal (patient does not pass), newborns are given the audi-tory brainstem response test (ABR) (most accurate hearing measure through age6 months). Sounds are presented through a small earphone, measured with headelectrodes, and analyzed by a computer.•Normal OAE: intact hearing through the cochlea•Normal ABR: also establishes the integrity of the auditory nerveAs for the causes of hearing loss, up to 60% prelingual isgenetic(>60 gene loci, >500 syndromeswith hearing loss); 70-80% is autosomal recessive, with 50% having a defect in connexin 26(a gap junction protein). Examples include Waardenburg syndrome (most common autosomaldominant condition with hearing loss), neurofibromatosis-2 (AD),Alport syndrome(AR).Up to 25% are nongenetic and up to 25% are idiopathic. Examples includeCMV(most com-mon congenital cause; then other congenital infections); otitis media with effusion (OME)(most common childhood cause); bacterial meningitis, especiallypneumococcus(occursearly and in >30%); trauma, especially to temporal bone; medication (aminoglycosides, loopdiuretics, cisplatin); acoustic (loud music, especially with earbuds/phones; audiograms showhigh-frequency loss at 4,000 Hz).FETAL GROWTH AND MATURITYTable 1-5. Intrauterine Growth Restriction (IUGR)TypeReasonMain EtiologiesComplicationsSymmetricEarly, in uteroinsult thataffects growthof most organsGenetic syndromes,chromosomalabnormalities, congenitalinfections, teratogens,toxinsEtiology dependent;delivery of oxygen andnutrients to vital organsusually normalAsymmetric(head sparing)Relatively lateonset after fetalorgandevelopment;abnormaldelivery ofnutritionalsubstances andoxygen to thefetusUteroplacentalinsufficiency secondary tomaternal diseases(malnutrition, cardiac,renal, anemia) and/orplacental dysfunction(hypertension,autoimmune disease,abruption)Neurologic (asphyxia) ifsignificant decreaseddelivery of oxygen tobrain

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6USMLE Step 2 CKlPediatricsGestational Age and Size at BirthPretermLarge for Gestational Age(LGA)—Fetal MacrosomiaPost-term•Premature—liveborninfants delivered prior to37 weeks as measuredfrom the first day of thelast menstrual period•Low birth weight (<2,500grams), possibly due toprematurity, IUGR, orboth•Birth weight >4,500grams at term•Predisposing factors:obesity, diabetes•Higher incidence of birthinjuries and congenitalanomalies•Infants born after 42weeks’ gestation from lastmenstrual period•When delivery is delayed≥3 weeks past term,significant increase inmortality•Characteristics–Increased birth weight–Absence of lanugo–Decreased/absentvernix–Desquamating, pale,loose skin–Abundant hair, longnails–If placental insufficiency,may be meconiumstainingENDOCRINE DISORDERSInfants of Diabetic MothersYou are called to see a 9.5-pound newborn infant who is jittery. Physical exam revealsa large plethoric infant who is tremulous. A murmur is heard. Blood sugar is low.•Maternal hyperglycemia (types I and II DM)→fetal hyperinsulinemia•Insulin is the major fetal growth hormone→increase in size of all organs exceptthe brain•Major metabolic effect is at birth with sudden placental separation→hypoglycemia•Infants may belarge for gestational age and plethoric(ruddy).•Othermetabolic findings: hypocalcemia and hypomagnesemia (felt to be a resultof delayed action of parathyroid hormone)•Common findings–Birth trauma(macrosomia)–Tachypnea(transient tachypnea, respiratory distress syndrome, cardiac failure,hypoglycemia)–Cardiomegaly—asymmetric septal hypertrophy(insulin effect, reversible)–Polycythemia (and hyperviscosity)→hyperbilirubinemia→jaundice

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Chapter 1lThe Newborn7–Renal vein thrombosis(flank mass, hematuria, thrombocytopenia) from polycythemia–Increased incidence of congenital anomalies°Cardiac—especially VSD, ASD, transposition°Small left colon syndrome(transient delay in development of left side ofcolon; presents with abdominal distention)°Caudal regression syndrome:spectrum of structural neurologic defects ofthe caudal region of spinal cord which may result in neurologic impairment(hypo, aplasia of pelvis & LE)•Prognosis—Infants of diabetic mothers are more predisposed to diabetes and LGAinfants are at increased risk of childhood obesity.•Treatment—careful monitoring and glucose control during pregnancy + closemonitoring of infant after delivery; early frequent feeds (oral, NG if hypoglycemiacontinues) followed by IV dextrose if euglycemia has not resultedClinical RecallWhich of the following is commonly seen in infants of diabetic mothers?A.MicrosomiaB.Small heart sizeC.PolycythemiaD.Renal artery thrombosisE.Slow respiratory rateAnswer: CRESPIRATORY DISORDERSPneumoniaChoanal atresiaRespiratory DistressRespiratoryNonrespiratoryRespiratorydistresssyndromeTransienttachypneaof thenewbornMeconiumaspirationsyndromeDiaphragmatic herniaCardiac: cyanotic CHDHeme:anemia, polycythemiaOther:infectious, metabolic, neurologicFigure 1-1.Respiratory Distress

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8USMLE Step 2 CKlPediatricsRespiratory Distress Syndrome (RDS)Shortly after birth, a 33-week gestation infant develops tachypnea, nasal flaring,and grunting and requires intubation. Chest radiograph shows a hazy, ground-glassappearance of the lungs.•Deficiency ofmature surfactant(surfactant matures over gestation with the additionof phosphatidyl groups; therefore, the incidence of surfactant deficiency diminishestowardterm.)•Inability to maintain alveolar volume at end expiration→decreased functionalresidualcapacity and atelectasis•Primary initial pulmonary hallmark ishypoxemia.Then,hypercarbia and respiratoryacidosis ensue.•Diagnosis–Best initial diagnostic test—chest radiograph°Findings:ground-glass appearance, low lung volume, air bronchograms–Most accurate diagnostic test—L/S ratio(part of complete lung profile; lecithin-to-sphingomyelin ratio)°Done on amniotic fluid prior to birth•Best initial treatment—oxygen•Most effective treatment—intubation and exogenous surfactant administration•Primary prevention– Avoid prematurity (tocolytics)–Antenatal betamethasoneTransient Tachypnea of the Newborn (TTN)•Slow absorption of fetal lung fluid→decreased pulmonary compliance and tidalvolume with increased dead space•Tachypnea after birth•Generally minimal oxygen requirement•Common in term infant delivered by Cesarean sectionor rapid second stageof labor•Chest x-ray (best test)—air-trapping, fluid in fissures, perihilar streaking•Rapid improvement generally within hours to a few daysMeconium Aspiration•Meconium passed as a result of hypoxia and fetal distress; may be aspirated in utero orwith the first postnatal breath→airway obstruction and pneumonitis→failure andpulmonary hypertension•Chest x-ray (best test)—patchy infiltrates, increased AP diameter, flattening ofdiaphragm•Other complications—air leak (pneumothorax, pneumomediastinum)

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