Skeletal Muscle Disease 

     This category includes diseases involving skeletal muscle atrophy,
     neuromuscular junction dysfunction, and primary myopathies.

Muscle Atrophy	Myasthenia gravis
Muscular Dystrophy	Inflammatory Myopathy
Tumors

Muscle Atrophy 

     The most common forms include neurogenic atrophy and Type II fiber atrophy.

     Neurogenic atrophy

          Damage to ant. horn cells or peripheral nerve.
          Angular atrophy of both type I and II fibers
          Group typing

     Type II fiber atrophy

          Immobility, advanced age, corticosteroids,
          Angular atrophy
          Lack of group typing

Myasthenia Gravis 

     Autoimmune disorder resulting in inhibition of neuromuscular transmission and
     skeletal muscle weakness.  Incidence = 1/20,000. Age 30-60.

     Evidence: 90% of patients have Ab's to AchR.
                         Immunoglobulins and activated complement in
                         neuromuscular junction.
                         Thymus hyperplasia/thymoma

     Clinical:      Weakness increases with activity.
                         Ptosis/diplopia          50%
                         Dysarthria/dysphagia     30%
                         Limb weakness            20%
                         Tensilon test

     Course:   Highly variable
               Ocular Myasthenia 
               Remissions/exacerbations
               Death from respiratory failure

Inflammatory Myopathies 

     Inflammation may result from infection, autoimmune disorders, or as a
     component of muscular dystrophy.  A classic form of an inflammatory
     myopathy is autoimmune.

     Polymyositis/Dermatomyositis

          Rare autoimmune disorders often seen in conjunction with scleroderma
          and lupus.

          Clinical: Lymphocytic infiltration
                    Antinuclear antibodies
                    Proximal muscle weakness
                    Periorbital rash
                    Myoglobinuria

Muscular Dystrophies 
     A group of disorders that have in common genetic basis leading to progressive
     degeneration of skeletal muscle.

     Duchenne Muscular Dystrophy
          X-linked recessive disorder (30% spontaneous mutation rate) resulting
          from a mutation in the gene coding for the product, dystrophin.  Patients
          with this disorder do not produce detectable amounts of this structural
          protein.
          Clinical: Age of onset 1-5 yrs.
                    Patient normal at birth.
                    Walking delayed.
                    Inflammatory cell infiltration
                    Progressive proximal muscle weakness.
                    Pseudohypertrophy
          Course:   Typical patient is wheelchair bound by teens and dies in their
                    20's.  Death often due to cardiac or respiratory
                    failure/infection.
     
Becker's Muscular Dystrophy
          Progressive X-linked recessive muscular disease involving the gene coding
          for dystrophin.  In this disease low molecular weight product is produced.
          Clinical: Age of onset 5-25 yrs.
                    Progressive muscle weakness.
          Course:   Many patients have normal life span.
     Myotonic Muscular Dystrophy
          Most common form of adult onset (age 30-40) muscular dystrophy.  This
          disease is inherited as an autosomal dominant trait (Chr. 19 - protein
          kinase).
          Clinical: Sustained involuntary muscle contraction.
                    Gait instability
                    Weakness in hand and foot
                    Ptosis
                    Frontal balding
                    Gonadal atrophy
                    Cardiomyopathy                

Soft Tissue Tumors 
     Any nonepithelial tissue that doesn't include bone, cartilage, brain, meninges,
     hematopoietic cells, or lymphoid tissue.

Adipose Tissue                Primarily adult
     Lipoma                   Most common STT.
     Liposarcoma         

Fibrous Tissue                Primarily adult
     Fibrosarcoma   

Skeletal Muscle
     Rhabdomyoma              Rare - adult
     Rhabdomyosarcoma         Most common in children

Smooth Muscle
     Leiomyoma                Adult women
     Leiomyosarcoma           Same