involvement of the cardiac and the skeletal muscles Chest radiography will show the associated deformities of the bony thorax together with an elevated hemidiaphragm The cardiac silhouette is normal Death from cardiac involvement is almost always caused by complete atrioventricular block or ventricular tachycardia It is very rarely caused by myocardial failure The most common abnormalities in the ECG are low amplitudes of the P wave, atrioventricular block of any degree, right and left bundle branch block, abnormal Q waves, and changes in the ST segment and T wave It is believed that regional myocardial dystrophy is responsible for the abnormal Q waves.242 Rhythm disturbances include sinus bradycardia, premature atrial beats, atrial fibrillation, atrial flutter, ventricular premature beats, and ventricular tachycardia Four-fifths of the patients have electrophysiologic evidence of disease of the atrioventricular conduction axis A further one-fifth have evidence of intra-atrial conduction disturbances.243 Disease of the atrioventricular conduction axis progresses with time A correlative study revealed fibrosis of the right and left bundle branches and fatty infiltration and degeneration around the atrioventricular node, which corresponded accurately with the ECG and electrophysiologic evaluation performed during life.244 Mitral valve prolapse is frequently associated with myotonic muscular dystrophy and is diagnosed echocardiographically It is present in approximately one-third of patients There is no relationship, however, between mitral valve prolapse and the arrhythmias Systolic and diastolic function is normal, although some patients fail to show an increase in ejection fraction with exercise Apical hypokinesia may be present but is of doubtful significance Careful clinical examination and a high degree of suspicion are required for an early diagnosis Electromyography and muscle biopsy are useful techniques, as is slit-lamp examination for cataracts Regular cardiac evaluation is required in all patients because of the frequent association of heart disease The diseases show progressive deterioration, with physical incapacity 15 to 20 years after the onset of muscular symptoms Death is usually from respiratory infections, aspiration, cardiac arrhythmias, or anesthetic complications There is no specific treatment for the condition Active exercise and weight control are important general therapeutic measures Systemic complications are treated as they arise Myotonia is relieved by the use of procainamide or phenytoin (diphenylhydantoin) Caution must be exercised, however, since procainamide exacerbates preexisting conduction disturbances Electrophysiologic studies are warranted in symptomatic patients presenting with syncope or presyncope A ventricular pacemaker is needed when there are significant abnormalities in the formation or conduction of the cardiac impulse Myotonic muscular dystrophy appears and progresses during early adult life in the majority of those affected In a proportion, however, the disease is present at birth Such congenital cases are often treated as a separate entity Indeed, as will be seen, they have a totally different presentation and clinical picture Nonetheless, in the fullness of time they come to resemble the adult form The congenital form is characterized by bilateral facial weakness, hypotonia, and mental retardation with delayed motor and speech development Neonatal respiratory distress is very frequent Such infants have a high incidence of feeding difficulties owing to muscle weakness Talipes is a common association Clinical myotonia is absent but can be demonstrated electromyographically The adult features of the disease appear during late childhood and adolescence Cardiac involvement takes the form of a dilated cardiomyopathy Nonspecific electrocardiographic abnormalities appear with progression of the disease Mortality occurs in the neonatal period as a result of respiratory distress Beyond this time, there is a tendency to improve, only for the patients to deteriorate as the adult characteristics of the disease appear The condition is transmitted by the mother Previously her clinical involvement has often been missed Autosomal Dominant Scapuloperoneal Myopathy Scapuloperoneal myopathy is a very rare form of muscular dystrophy Two distinct groups are recognized according to the age of onset They share an autosomal dominant form of inheritance and involve the same muscle groups Weakness and atrophy affects the neck, shoulder girdle, and upper arm muscles together with the tibial and peroneal muscles in the legs Foot drop and an awkward gait are frequent early symptoms Deep tendon reflexes are commonly absent Serum levels of creatine kinase are slightly elevated Electromyography and muscle biopsy show the changes common to muscular dystrophies Patients with early onset generally present under the age of 10 years, and in these the disease takes a rapid course Patients develop early contractures and are severely incapacitated by their late teens They frequently have clinical and electrocardiographic signs of a dilated cardiomyopathy with CHF.245 Those having a late onset present over the age of 40 years and the clinical course is slow They seldom develop contractures Cardiac involvement, usually late, could well be a result of ischemic heart disease.246 Becker Muscular Dystrophy Becker muscular dystrophy is one of the most frequent types of muscular dystrophy and is inherited in X-linked recessive fashion The incidence is of the order of 3 to 6 per 100,000 male births The muscular groups involved are very similar to those in Duchenne muscular dystrophy The peroneal and anterior tibial muscles are also affected in the Becker form of dystrophy The facial muscles are not involved Calf hypertrophy and muscle cramps are frequent early symptoms Club feet are often seen Contractures appear in the final stages and scoliosis is rare Developmental delay is uncommon The onset of the symptoms is between 5 and 15 years of age, with inability to walk being present by the third decade and death occurring in the fifth The individual range, however, is very wide The diagnosis is primarily clinical Serum creatine kinase activity is 25 to 200 times normal The electromyogram and the muscle biopsy are nonspecific but help to rule out other conditions Cardiac abnormalities are infrequent in childhood but are almost always present in some form by the onset of the fourth decade.247 ECG abnormalities are common and include resting tachycardia, interventricular conduction delay, and Q waves in leads II, III, and AVF, suggesting damage to the lateral wall of the left ventricle.248 Heart rate variability is also decreased and may indicate risk for sudden death.249 Dilated cardiomyopathy associated with Becker muscular dystrophy is also seen The risk of ventricular dysfunction increases with age, although many patients are asymptomatic from a cardiac standpoint and exhibit abnormalities only on the ECG or echocardiogram.250 Heart transplantation for severe left ventricular systolic dysfunction is a well-established palliative option.251 Facioscapulohumeral Muscular Dystrophy (Landouzy-Déjérine Syndrome) Facioscapulohumeral muscular dystrophy is inherited in an autosomal dominant fashion It has an incidence of approximately 5 per 100,000 live births Facial and shoulder weakness generally develop in the second or third decade and progress very slowly Patients with severe forms of this disease will occasionally