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Duchenne Muscular Dystrophy

- Discussion:
    - is the most severe and is the most common of the dystrophies;
    - clinical manifestations are usually obvious by 3 years of age, with child experiencing particular difficulty in running and climbing;
          - toe walking may be an early manifestation;
    - proximal muscles are more severely affected than the distal;
    - some muscles, particularly gastrocnemius, may be large and bulky, although weak, a condition termed pseudohypertrophy;
    - proximal muscle weakness progresses; child is often restricted to wheelchair before 10 years of age;
    - pts usually die of cardiorespiratory complications before age 20 yr;
    - ref: Images in Clinical Medicine: Muscular Dystrophy
    - genetics:
          - it is transmitted as an X-linked recessive disease;
                - DNA chromosome analysis in these pts is almost 100% accurate in determining either carrier state or disease in the fetus;
          - females are carriers and show no, or only very mild, clinical effects, but males are severely incapacitated;
                - two thirds of affected patients or female carriers have deletion of XP-21 chromosome;
                - in remaining third, genetic linkage studies and measurement of CPK levels may still identify the carrier;
     - differential diagnosis:
          - biopsy remains the most effective test for differentiating the various muscular dystrophies;
          - Myopathic Disorders
          - Becker Muscular Dystrophy
                - also sex linked recessive dystrophy but is less severe;
                - some of these patients may be color blind;
          - Facioscapulohumeral Muscular Dystrophy
                - autosomal dominant disorder typically seen in a 6-20 yo with facial muscle abnormalities, normal CPK, and winging of the 
                       scapula (stabilize the scapula w/ scapula thoracic fusion);
          - Limb Girdle:
                - autosomal recessive disorder (10-30 yo with pelvic or shoulder girdle involvement and decreased CPK)
                - this is a likely diagnosis in a female patient who displays clinical features of DMD;

- Laboratory Dx of Duchennes Muscular Dystropy

- Treatment:  
     - Malignant Hyperthermia
     - Cardiac:
             - patients w/ DMD are prone to Mitral Valve Prolapse, and should have ECHO prior to surgery;
             - these pts are also prone to arrhythymias under anesthesia;
             - PFTs (note FEV1) and ABG;
     - Contractures of the Upper Extremities
     - Contractures of the Lower Extremities
             - treatment is based on keeping pt ambulatory as long as possible;
             - KAFO bracing and release of contractures are important;
             - hip extensors are the first muscle group to be involved;
             - child may be noted to be an early toe walker;
             - equinus contractures:
     - Scoliosis

Progression of scoliosis in Duchenne muscular dystrophy.

Spinal stabilisation in Duchenne muscular dystrophy.

Prednisone in Duchenne dystrophy. A randomized, controlled trial defining the time course and dose response. Clinical Investigation of Duchenne Dystrophy Group.

Advantage of early spinal stabilization and fusion in patients with Duchenne muscular dystrophy

Scoliosis associated with Duchenne muscular dystrophy.    

The effect of spine fusion on respiratory function in Duchenne muscular dystrophy.   

Steroid Treatment and the Development of Scoliosis in Males with Duchenne Muscular Dystrophy.

Should Foot Surgery Be Performed for Children With Duchenne Muscular Dystrophy?