Question

List and describe one Muscle Abnormality. It could be a disease or condition. Or it could be something that happens with exercise. Be sure to describe what structures are affected within the muscle. List the symptoms of this abnormality, as well as one possible treatment option.

Answer 1

Here i would like to share about duchenne and beckers muscular dystrophy.  

It is an X linked muscular dystrophy with dystrophin mutation .

They are also called as dystrophinopathies.

When it has an early onset it is calles duchenne muscular dystrophy and the progression is severe. Because it is associated with deletion or frameshift mutations which causes total absence of dystrophin.

Whereas beckers muscular dystrophy has a late onset and has a mild progressive phenotype. Because dystrophin is produced in truncated versions where some of its functions are preserved.

PATHOGENESIS:

• It is caused by loss of function mutation in dystrophin gene located in the X chromosome.  
• This gene encodes a protein called dystrophin. Which is a component of dystrophin glycoprotein complex. This serves as a link between cytoskeleton inside the myofiber and basement membrane outside the cell. It links between actin filaments in cytoplasm of myofibers and beta dystroglycan in the transmembrane protein .
• So this provides a mechanical stability to the myofibres during contraction. So defects in these protein leads to calcium influx which causes degeneration of myofibres.

SYMPTOMS:

• They are normal at birth
• Early milestones are met
• The foremost indication is inability to keep upwith peers and clumsiness
• Pelvic girdle muscles are affected which extend upto shoulder girdle
• Pseudohypertrophy and weakness of lower limb seen .
• Patient depends on wheelchair by the age of 10
• dystrophin is also present in heart and cns , so deficit leads to cardiomyopathy and arrhythmias. In cns sometimes mental retardation seen . Also cognitive impairment seen .
• Whereas beckers dystrophy presents with later childhood , adolescents or adults.  
• Diagnosis will be based on history, physical examination , and serum creatinase level will be elevated due to muscular damage .

Possible treatment:

• supportive measures given .
• Definitive therapy requires dystrophin level restoration in skeletal and cardiac muscle , but it is quite challenging.  
• Drugs which promote read through of stop codon in the ribosome may enable the dystrophin expression. Gene therapy projects have also been going through.  
• Drugs like steroids can be given , medication like ace inhibitors and beta blocker given when heart muscles are damaged , exercise is must to prevent immobility and fixation of joints . Walking aids , breathing aids given .
• Despite supportive care patient dies at 25 to 30 yrs due to heart failure , respiratory infections, respiratory insufficiency.