Muscular dystrophy is a group of hereditary disorders characterized by progressive symmetrical wasting of skeletal muscles but no neural or sensory defects. Four main types of muscular dystrophy occur: Duchenne's (pseudohypertrophic) muscular dystrophy, which accounts for 50% of all cases; Becker's (benign pseudohypertrophic) muscular dystrophy; Landouzy-Dejerine (facioscapulohumeral) dystrophy; and Erb's (limb-girdle) dystrophy. Duchenne's and Becker's muscular dystrophies affect males almost exclusively. The other two types affect both sexes about equally.
Depending on the type, the disorder may affect vital organs and lead to severe disability, even death. Early in the disease, muscle fibers necrotize and regenerate in various states. Over time, regeneration slows and degeneration dominates. Fat and connective tissue replace muscle fibers, causing weakness.
The prognosis varies. Duchenne's muscular dystrophy typically begins during early childhood and causes death within 10 to 15 years. Patients with Becker's muscular dystrophy may live into their 40s. Landouzy-Dejerine and Erb's dystrophies usually don't shorten life expectancy.
Muscular dystrophy is caused by various genetic mechanisms. The basic defect can be mapped genetically to band Xp 21. Duchenne's and Becker's muscular dystrophies are X-linked recessive, and LandouzyDejerine dystrophy is autosomal dominant. Erb's dystrophy may be inherited in several ways but usually is autosomal recessive.
Exactly how these inherited defects cause progressive muscle weakness isn't known. They may create an abnormality in the intracellular metabolism of muscle cells. The abnormality may be related to an enzyme deficiency or dysfunction, or to an inability to synthesize, absorb, or metabolize an unknown substance vital to muscle function.
Signs and Symptoms
Principal symptoms include:
Several tests are used to help confirm the diagnosis:
Currently, no treatment can stop the progressive muscle impairment. Orthopedic appliances, exercise, physical therapy, and surgery to correct contractures can help preserve the patient's mobility and independence.
Genetic counseling is advised when there is a family history of muscular dystrophy. Women may have no symptoms but still carry the gene for the disorder. Duchenne muscular dystrophy can be detected with about 95% accuracy by genetic studies performed during pregnancy.
(c)Copyright Medical-clinic.org All rights reserved.
Disclaimer : All information on Medical-clinic.org is for educational and information purposes only. For specific medical advice, diagnoses, and treatment, please consult your doctor. We will not be liable for any complications, or other medical accidents arising from the use of any information on this web site.