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Laboratory Dx of Duchennes Muscular Dystropy

- CPK:
    - normal CPK is approximately 200 units;
    - in DMD, CPK can be elevated 10-20 fold, but may be as high as 10,000 IU/L;
    - serum CPK may also be elevated in limb girdle dystrophy, dermatomyositis, type IV spinal muscular atrophy, but will not be elevated as 
           high as DMD;
    - marked elevation of SGOT may be elevated in polymyositis;

- Dystrophin:
    - absence or deficiency of dystrophin on surface membrane of muscle cells is a key marker for this disease and has facilitated determination 
           of female carriers;
           - one may also identify female characters by measuring CPK levels;
    - assessment of dystrophin levels on muscle biopsy also provides an index of prognosis for severity of the muscular dystrophy

- Biopsy:
    - muscle biopsy is the most effective test to distinguish the various muscular dystrophies;
    - general histological features include:
           - variation in fiber size;
           - central location of muscle fibers;
           - degeneration of regional muscle fibers