...Is it larger with maternal transmissions? Or is there an identical distribution between men and women?
Myotonic dystrophy is an inherited disease where a change, called a mutation, has occurred in a gene required for normal muscle function. The mutation prevents the gene from carrying out its function properly.
DNA is the genetic material found in the nucleus of nearly every cell. A gene is a stretch of DNA that carries a set of instructions on how a protein should be made. These proteins carry out the functions of the body. Scientists estimate that humans have about 25,000 different genes.
Both DM1 and DM2 are passed from parent to child by autosomal dominant mutations. This means that the faulty gene is located on one of the chromosomes that does not determine sex (autosome) and that one copy of the mutated gene is enough to cause the disease (dominant).
Studies have been done to understand how these non-coding mutations could have a trans-dominant effect (i.e. how they could affect other genes not associated with the mutation locus). This research suggests a gain-of-function RNA mechanism underlies the clinical features common to both diseases.
Myotonic dystrophy is one of the most complex disorders known. In addition to the incredible variability of clinical symptoms, the disease also has unique mechanistic features:
Myotonic dystrophy is one of the most complex disorders known. In addition to the incredible variability of clinical symptoms, the disease also has several unique mechanistic features:
Tissues in affected individuals can have unstable expanded regions. Once repeat counts reach an approximate threshold (>35 repeats for DM1 and >75 repeats in DM2), these sequences become highly unstable in both the soma and germ line.
Myotonic dystrophy (DM) was the first autosomal dominant disease found to be caused by a repeat expansion that is transcribed into RNA, but is not translated into protein.
Because expansion of the CTG repeats commonly occurs during meiosis, the repeat count tends to increase over successive generations. As a result, children of affected individuals (including those with the pre-mutation) tend to experience more severe symptoms at an earlier age than their parent.
Genetic testing (also referred to as DNA testing) is a definitive diagnostic of whether or not a person has DM. DNA, the genetic material in the nucleus of cells, is isolated from a sample of blood or other tissue, and then analyzed to determine whether or not a specific mutation is present.
Myotonic dystrophy is one of the most complex disorders known. In addition to the incredible variability of clinical symptoms the disease also has unique mechanistic features:
Myotonic dystrophy is a very complicated condition. The symptoms and disease progression can vary widely. The effects can be quite different even among members of the same family, so it is difficult to predict just how the disorder will affect you and your family.