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involvementofthecardiacandtheskeletalmuscles.Chestradiographywill
showtheassociateddeformitiesofthebonythoraxtogetherwithanelevated
hemidiaphragm.Thecardiacsilhouetteisnormal.Deathfromcardiac
involvementisalmostalwayscausedbycompleteatrioventricularblockor
ventriculartachycardia.Itisveryrarelycausedbymyocardialfailure.
ThemostcommonabnormalitiesintheECGarelowamplitudesoftheP
wave,atrioventricularblockofanydegree,rightandleftbundlebranchblock,
abnormalQwaves,andchangesintheSTsegmentandTwave.Itisbelieved
thatregionalmyocardialdystrophyisresponsiblefortheabnormalQwaves.242
Rhythmdisturbancesincludesinusbradycardia,prematureatrialbeats,atrial
fibrillation,atrialflutter,ventricularprematurebeats,andventricular
tachycardia.Four-fifthsofthepatientshaveelectrophysiologicevidenceof
diseaseoftheatrioventricularconductionaxis.Afurtherone-fifthhaveevidence
ofintra-atrialconductiondisturbances.243Diseaseoftheatrioventricular
conductionaxisprogresseswithtime.Acorrelativestudyrevealedfibrosisofthe
rightandleftbundlebranchesandfattyinfiltrationanddegenerationaroundthe
atrioventricularnode,whichcorrespondedaccuratelywiththeECGand
electrophysiologicevaluationperformedduringlife.244
Mitralvalveprolapseisfrequentlyassociatedwithmyotonicmuscular
dystrophyandisdiagnosedechocardiographically.Itispresentinapproximately
one-thirdofpatients.Thereisnorelationship,however,betweenmitralvalve
prolapseandthearrhythmias.Systolicanddiastolicfunctionisnormal,although
somepatientsfailtoshowanincreaseinejectionfractionwithexercise.Apical
hypokinesiamaybepresentbutisofdoubtfulsignificance.
Carefulclinicalexaminationandahighdegreeofsuspicionarerequiredforan
earlydiagnosis.Electromyographyandmusclebiopsyareusefultechniques,as
isslit-lampexaminationforcataracts.Regularcardiacevaluationisrequiredin
allpatientsbecauseofthefrequentassociationofheartdisease.Thediseases
showprogressivedeterioration,withphysicalincapacity15to20yearsafterthe
onsetofmuscularsymptoms.Deathisusuallyfromrespiratoryinfections,
aspiration,cardiacarrhythmias,oranestheticcomplications.

Thereisnospecifictreatmentforthecondition.Activeexerciseandweight
controlareimportantgeneraltherapeuticmeasures.Systemiccomplicationsare
treatedastheyarise.Myotoniaisrelievedbytheuseofprocainamideor
phenytoin(diphenylhydantoin).Cautionmustbeexercised,however,since
procainamideexacerbatespreexistingconductiondisturbances.
Electrophysiologicstudiesarewarrantedinsymptomaticpatientspresenting


withsyncopeorpresyncope.Aventricularpacemakerisneededwhenthereare
significantabnormalitiesintheformationorconductionofthecardiacimpulse.
Myotonicmusculardystrophyappearsandprogressesduringearlyadultlifein
themajorityofthoseaffected.Inaproportion,however,thediseaseispresentat
birth.Suchcongenitalcasesareoftentreatedasaseparateentity.Indeed,aswill
beseen,theyhaveatotallydifferentpresentationandclinicalpicture.
Nonetheless,inthefullnessoftimetheycometoresembletheadultform.The
congenitalformischaracterizedbybilateralfacialweakness,hypotonia,and
mentalretardationwithdelayedmotorandspeechdevelopment.Neonatal
respiratorydistressisveryfrequent.Suchinfantshaveahighincidenceof
feedingdifficultiesowingtomuscleweakness.Talipesisacommonassociation.
Clinicalmyotoniaisabsentbutcanbedemonstratedelectromyographically.The
adultfeaturesofthediseaseappearduringlatechildhoodandadolescence.
Cardiacinvolvementtakestheformofadilatedcardiomyopathy.Nonspecific
electrocardiographicabnormalitiesappearwithprogressionofthedisease.
Mortalityoccursintheneonatalperiodasaresultofrespiratorydistress.Beyond
thistime,thereisatendencytoimprove,onlyforthepatientstodeteriorateas
theadultcharacteristicsofthediseaseappear.Theconditionistransmittedbythe
mother.Previouslyherclinicalinvolvementhasoftenbeenmissed.

AutosomalDominantScapuloperoneal
Myopathy

Scapuloperonealmyopathyisaveryrareformofmusculardystrophy.Two
distinctgroupsarerecognizedaccordingtotheageofonset.Theysharean
autosomaldominantformofinheritanceandinvolvethesamemusclegroups.
Weaknessandatrophyaffectstheneck,shouldergirdle,andupperarmmuscles
togetherwiththetibialandperonealmusclesinthelegs.Footdropandan
awkwardgaitarefrequentearlysymptoms.Deeptendonreflexesarecommonly
absent.Serumlevelsofcreatinekinaseareslightlyelevated.Electromyography
andmusclebiopsyshowthechangescommontomusculardystrophies.
Patientswithearlyonsetgenerallypresentundertheageof10years,andin
thesethediseasetakesarapidcourse.Patientsdevelopearlycontracturesandare
severelyincapacitatedbytheirlateteens.Theyfrequentlyhaveclinicaland
electrocardiographicsignsofadilatedcardiomyopathywithCHF.245Those
havingalateonsetpresentovertheageof40yearsandtheclinicalcourseis
slow.Theyseldomdevelopcontractures.Cardiacinvolvement,usuallylate,


couldwellbearesultofischemicheartdisease.246

BeckerMuscularDystrophy
Beckermusculardystrophyisoneofthemostfrequenttypesofmuscular
dystrophyandisinheritedinX-linkedrecessivefashion.Theincidenceisofthe
orderof3to6per100,000malebirths.Themusculargroupsinvolvedarevery
similartothoseinDuchennemusculardystrophy.Theperonealandanterior
tibialmusclesarealsoaffectedintheBeckerformofdystrophy.Thefacial
musclesarenotinvolved.Calfhypertrophyandmusclecrampsarefrequent
earlysymptoms.Clubfeetareoftenseen.Contracturesappearinthefinalstages
andscoliosisisrare.Developmentaldelayisuncommon.Theonsetofthe
symptomsisbetween5and15yearsofage,withinabilitytowalkbeingpresent
bythethirddecadeanddeathoccurringinthefifth.Theindividualrange,
however,isverywide.Thediagnosisisprimarilyclinical.Serumcreatinekinase

activityis25to200timesnormal.Theelectromyogramandthemusclebiopsy
arenonspecificbuthelptoruleoutotherconditions.
Cardiacabnormalitiesareinfrequentinchildhoodbutarealmostalways
presentinsomeformbytheonsetofthefourthdecade.247ECGabnormalities
arecommonandincluderestingtachycardia,interventricularconductiondelay,
andQwavesinleadsII,III,andAVF,suggestingdamagetothelateralwallof
theleftventricle.248Heartratevariabilityisalsodecreasedandmayindicaterisk
forsuddendeath.249DilatedcardiomyopathyassociatedwithBeckermuscular
dystrophyisalsoseen.Theriskofventriculardysfunctionincreaseswithage,
althoughmanypatientsareasymptomaticfromacardiacstandpointandexhibit
abnormalitiesonlyontheECGorechocardiogram.250Hearttransplantationfor
severeleftventricularsystolicdysfunctionisawell-establishedpalliative
option.251

FacioscapulohumeralMuscularDystrophy
(Landouzy-DéjérineSyndrome)
Facioscapulohumeralmusculardystrophyisinheritedinanautosomaldominant
fashion.Ithasanincidenceofapproximately5per100,000livebirths.Facial
andshoulderweaknessgenerallydevelopinthesecondorthirddecadeand
progressveryslowly.Patientswithsevereformsofthisdiseasewilloccasionally