Muscular dystrophy (MD) is caused by genetic mutations affecting the genes responsible for the structure and function of muscles. These mutations disrupt the production of proteins crucial for building and maintaining healthy muscle tissue, leading to progressive muscle weakness and disability.
Understanding the Genetic Basis
The core problem in muscular dystrophy lies within a person's DNA. Specific genes hold the instructions for making proteins that muscles need to function correctly. When a mutation, or alteration, occurs in one of these genes, the protein it codes for may be:
- Missing entirely: The protein simply isn't produced.
- Deficient in quantity: Not enough of the protein is made.
- Malfunctioning: The protein is produced, but it doesn't work correctly.
How These Mutations Affect Muscles
These faulty proteins compromise the integrity of muscle fibers. Healthy muscles go through a constant cycle of breakdown and repair. Without the proper proteins, this cycle is disrupted. Muscle cells become damaged and weaken over time. Eventually, the damaged muscle tissue may be replaced by fatty and connective tissue, further weakening the muscles.
Examples of Affected Proteins and Genes
Different types of muscular dystrophy are associated with mutations in different genes. Here are a few examples:
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Duchenne and Becker Muscular Dystrophy: These are the most common forms, caused by mutations in the DMD gene, which is responsible for producing dystrophin, a protein that helps strengthen muscle fibers.
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Myotonic Dystrophy: Caused by mutations in the DMPK or CNBP genes, affecting muscle relaxation after contraction.
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Facioscapulohumeral Muscular Dystrophy (FSHD): Usually associated with deletions in the DUX4 region of chromosome 4, leading to the abnormal expression of the DUX4 gene.
Inheritance Patterns
Muscular dystrophy can be inherited in several ways, depending on the specific gene involved:
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X-linked recessive: This is how Duchenne and Becker MD are often inherited. The gene is located on the X chromosome. Males, having only one X chromosome, are more likely to be affected. Females with one affected X chromosome are usually carriers.
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Autosomal dominant: Only one copy of the mutated gene is needed to cause the disorder.
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Autosomal recessive: Two copies of the mutated gene are needed (one from each parent) to cause the disorder.
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De novo mutations: Sometimes, the genetic mutation occurs spontaneously in the affected individual and is not inherited from either parent.
In conclusion, muscular dystrophy is a group of genetic diseases caused by mutations in genes responsible for healthy muscle structure and function, leading to progressive muscle weakness and disability.
