University:
Western Sydney University
Course:
MEDI 2003 | Clinical Sciences 2
Academic year:

2024
Views:

135

Pages:

2
Author:

Mariam A.

Muscular dystrophy  Duchenne’s muscular dystrophy (DMD) is the most common and most severe form of this disease. Becker’s muscular dystrophy is less severe, even though there are mutations within the same gene as Duchenne’s. The frequency is about 1 in 3500 males and 1 in 20 000 females (X-linked recessive), and the common clinical presentations include slowly progressive muscle weakness, Gower’s sign, increase calf muscles size, some intellectual impairment (non-progressive cognitive impairment  possible autism). There is no effective cure for the disorder Dystrophin gene (mutated protein in this condition)    Part of a group of proteins that strengthen muscle fibres and protect them from injury as they contract and relax. It acts as an anchor, connecting the cytoskeleton to the extracellular matrix. It may also play a role in cell signalling Deletion account for 2/3 of all mutations in the gene. The more severe phenotypes (e.g. Duchenne’s) are due to a frameshift mutation, where entire exons can be deleted. Location of the mutation is important The absence of the dystrophin protein results in gradual muscle cell degeneration, due to disruption of the cell membrane’s integrity, where levels of <3% dystrophin in biopsies indicate DMD Screening tools  Multiplex Ligation-dependent Probe Amplification – Technique used to detect if exons are deleted Muscle regeneration  Humans do not usually regenerate new muscle fibres in adult life. Existing muscle fibres can resume growth if need be due to cells serving as myoblasts being retained. In damaged muscles, these satellite cells (stem cells of skeletal muscle) are activated to proliferate, where their progeny can fuse to repair damaged muscle.  In Duchenne’s muscular dystrophy, the process of repair by satellite cells is limited. Satellite cells do proliferate to repair the damaged muscle fibres, however the regeneration cannot keep pace with the degeneration. Connective tissue eventually replaces the muscle cells, blocking further regeneration.