Duchenne Muscular Dystrophy

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- 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;
    - 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

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- 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:

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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.
    Sussman MD:   Pediatr Orthop 1984;4:532-537.

Scoliosis associated with Duchenne muscular dystrophy.
      Cambridge W, Drennan JC:   J Pediatr Orthop   1987;7:436.

The effect of spine fusion on respiratory function in Duchenne muscular dystrophy.
    Miller RG, Chambers AC, Dao H, et al:   Neurology 1991;41:38.

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

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

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