How neuromuscular disorders are inherited?
Generally, in order for a hereditary disease to occur, there must be at least one change in DNA, the so called mutations. These occur quite often, but the human body has the potential to repair them in most cases. When this is not possible, genetic diseases manifest. In neuromuscular cases, mutations occur in DNA regions (genes and chromosomes) responsible for the proper structure and function of the muscle cells.
In order to inherit any feature in humans, there must be two copies of the corresponding genes, one of maternal and one of paternal origin. If either of these copies is changed, it will pass to the offspring. If for example dystrophy occurs, it depends on how each dystrophy is inherited, and in general any genetic disorder and of course neuromuscular disorders.
The way of inheritance could belong to any of the following categories:
- Autosomal recessive
- Autosomal dominant
Of course, the mutation may occur randomly (de novo) without a hereditary history.
- In cases of autosomal recessive disorders, two mutated gene copies have been inherited, one from each parent. Then there will be a disease. In case of inheritance of only one such gene, the individual is considered to be a carrier but not a patient. In this way, most of limb girdle muscular dystrophies are inherited.
- In cases of autosomal dominant disorders, it is sufficient to inherit a single gene from one parent in order to manifest the disease. In this way, some other limb girdle muscular dystrophies, oculopharyngeal muscular dystrophy, as well as other neuromyopathies, are inherited.
- Two of the 46 chromosomes of the human cell are responsible for the sex in the human species, X and Y chromosome, as they are called. Each person inherits one from each parent, so each woman has two X chromosomes and each man an X and a Y chromosome. In X-linked diseases the mutations refer to the X chromosome. Because of this, men suffer more often from such diseases if they have only one X, while a woman is rare to suffer because the information of a normal X chromosome will overlap the mutation. Representative disorders here are Duchenne and Becker Muscular Dystrophy.