Muscular dystrophy

Muscular dystrophy - Chronic
Rahul Soman, M. Pharm

 

Definition  

A group of hereditary disorders involving muscle protein dysfunction (deficient or abnormally formed protein), caused by mutations involving many different genes that are located on different chromosomes, resulting in different patterns of progressive muscle weakness, along with specific comorbid disorders .

 

Respiratory failure  

* Spirometry: A peak expiratory flow of 20% to 30% and an FEV1 of 20% to 30% of predicted normal values suggest significant airflow limitation and ventilatory effect.

 

Respiratory insufficiency  

* Pulse oximetry

 

Suspected obstructive sleep apnea  

* Polysomnography: More than 5 apneic episodes per hour of sleep, or 15 episodes without other findings, is important if sleepiness or other cardiovascular comorbidities exist

 

Evaluation for Sleep-Disordered Breathing and Alveolar Hypoventilation  

 

Suspected obstructive sleep apnea  

* Polysomnography: More than 5 apneic episodes per hour of sleep, or 15 episodes without other findings, is important if sleepiness or other cardiovascular comorbidities exist

 

Suspected alveolar hypoventilation in muscular dystrophy  

* Overnight pulse oximetry

 

Routine Evaluation of Cardiac Function  

 

Suspected or known muscular dystrophy  

* 12 lead ECG: Electrocardiography plays a key role in early detection of cardiomyopathy and cardiac conduction defects in muscular dystrophy .

 

Suspected and known dilated cardiomyopathy .  

* Transthoracic echocardiography

 

Findings  

* Difficulty running

* Difficulty walking up stairs

* Feeding problems in newborn

* Not yet walking

* Muscle atrophy

* Muscle weakness

* Mental retardation

* Coughing ineffective

* Hypoventilation

* Decreased cardiac function

* Dyspnea - Chronic

* Poor muscle tone

* Pseudohypertrophy of muscle

* Contracture of joint

* Myotonia

* Dysphagia - Chronic

* Ptosis of eyelid

* Hearing loss

* Nasal voice

* Abnormal vision

* Disorder of extraocular muscle

 

Tests  

 

Suspected muscular dystrophy  

* Serum creatine kinase measurement: Serum creatine kinase levels may be markedly elevated in some forms of muscular dystrophy; levels are high from birth in Duchenne muscular dystrophy .

 

Suspected muscular dystrophy .  

* Electromyography

 

Suspected muscular dystrophy  

* Biopsy of muscle: Typical muscle histological findings are variation in fiber sizes, fiber necrosis, presence of macrophages, and replacement by connective tissue and fat .

* Gene mutation analysis

 

Suspected muscular dystrophy  

* Immunohistochemistry procedure

* Western blot assay

 

Suspected or known muscular dystrophy  

* 12 lead ECG: Electrocardiography plays a key role in early detection of cardiomyopathy and cardiac conduction defects in muscular dystrophy .

 

Differential Diagnosis  

* Polymyositis

* Peripheral neuropathy - Chronic

* X-linked muscular dystrophy with abnormal dystrophin

* Congenital muscular dystrophy

* Limb-girdle muscular dystrophy

* Emery-Dreifuss muscular dystrophy

* Distal muscular dystrophy

* Facioscapulohumeral muscular dystrophy

* Oculopharyngeal muscular dystrophy

* Steinert myotonic dystrophy syndrome

 

Treatment  

 

Drug Therapy  

 

Duchenne muscular dystrophy  

 

PREDNISONE  

Pediatrics: 0.75 mg/kg/day orally; decrease as low as 0.3 mg/kg/day if necessary due to side effects

 

Procedural Therapy  

 

Ventilatory compromise in Duchenne muscular dystrophy  

* Respiratory therapy: Aggressive pulmonary care helps prevent respiratory complications and improves cardiac output by reducing afterload and left ventricular wall stress .

 

Respiratory failure  

* Noninvasive positive pressure ventilation: Most studies have shown favorable outcomes with the use of noninvasive positive pressure ventilation support for patients with respiratory failure ..

 

Respiratory failure  

* Mechanical ventilation: Early treatment of acute respiratory failure with mechanical ventilation may decrease morbidity, mortality, and length of hospitalization.

 

Non-Procedural Therapy  

 

Duchenne muscular dystrophy  

* Patient Education