. At age 4, James underwent a biopsy of the right gastrocnemius muscle. The pathologist's report noted histopathologic changes suggestive of Duchenne muscular dystrophy. Describe in detail the typical microscopic changes noted in the muscle tissue of someone with Duchenne's muscular dystrophy.

Answered below.

Explanation:

Duchenne's muscular dystrophy is a disease characterized by a progressive and severe muscle weakness. It affects the cardiac and respiratory muscles leading to death because of the failure of these muscles. Death usually occurs in early adulthood. The disease is inherited and is caused by mutations on the DMD gene.

Histological findings in this disease show whorled muscle fibres, increase in fatty replacement of muscles, increase in endomysial fibres, regeneration, necrosis and myofibre splitting.

There is an observable variation in the sizes of the myofibres, with large and hypertrophic fibres mixing with small and atrophied fibres. There's also an increased internal nuclei.

ANSWERS

DMD, is a recessive X-linked disorder characterised with muscle wasting(dystrophy).  

When the sample of the individual tissue was observed under microscope:

1. It was characterised with degenerated muscle fibers;

This is because dystophin, a structural protein which forms a connective networks between the internal cytoskeleton and external basal lamina in the muscle fibres is missing in the individuals (due to mutation.) Thus their muscle cells lack the typical and structure make up of a typical muscle fibre,consequently the muscles cells died, and degenerate.

2. Proliferation of connective tissues were observed around the degenerated fibre.  

This is because to make up for the lost cells, skeletal muscles divides to form small new fibres cells.However the rate of degeneration is faster than formation of new muscle fibers, thus proliferation of connective tissues due to dead cells covers the degenerated muscles cells.

3. Accumulation of dead cells attracts macrophages to the site,  

to engulf the dead cells,

4. Certain population of dark muscle fibres were observed.  

This is because of too many contraction of the these particular muscle fibres, as they some of them are losing there cell membranes, Since the muscle fibres are dead, Ca+ influx into the dead cells  caused extreem contractions,with the overlap of actin  with myosin.

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