Duchenne Muscular Dystrophy causes in adults
Duchenne Muscular Dystrophy (DMD) is widely recognized as a severe genetic disorder primarily diagnosed in boys during childhood. It is characterized by progressive muscle degeneration and weakness due to mutations in the dystrophin gene, which is essential for maintaining muscle cell integrity. While DMD is commonly identified in young males, there are cases where symptoms or related complications manifest or are diagnosed in adulthood. Understanding the causes and presentation of Duchenne muscular dystrophy in adults requires exploring the nuances of the disease’s genetics, progression, and possible atypical cases.
DMD is inherited in an X-linked recessive pattern, meaning the defective gene responsible for dystrophin production is located on the X chromosome. Since males have only one X chromosome, a single mutated copy of the gene typically results in the full-blown disease. Females, possessing two X chromosomes, are usually carriers of the mutation and often do not show severe symptoms due to the presence of a normal copy of the gene. However, in rare cases, females can manifest symptoms if they have skewed X-inactivation or other genetic anomalies.
Most individuals with Duchenne muscular dystrophy exhibit symptoms in early childhood, such as delayed motor milestones, frequent falls, and difficulty running or climbing stairs. As the disease progresses, muscle weakness spreads, affecting the respiratory and cardiac muscles, leading to life-threatening complications. Over time, the natural course of DMD often results in wheelchair dependence and a shortened lifespan, typically due to respiratory or cardiac failure.
In adult cases, the causes can be multifaceted. Some individuals with DMD survive into adulthood due to advances in medical care, including respiratory support, cardiac management, and physical therapy. These patients may have a milder disease course, possibly due to genetic factors such as residual dystrophin expression or less severe mutations in the dystrophin gene. For example, certain mutations may allow the production of a partially functional dystrophin protein, resulting in a less aggressive disease phenotype, often referred to as Becker muscular dystrophy, which is considered a milder, related form.
Additionally, in rare circumstances, adults may be diagnosed with DMD due to new mutations in the dystrophin gene, even if they have no family history of the disorder. These de novo mutations can occur spontaneously and lead to the development of DMD symptoms later in life, especially if the mutation results in a significant loss of dystrophin function.
Another factor to consider is the phenomenon of somatic mosaicism, where mutations occur after conception, leading to a mixture of cells with and without the mutation. Such mosaicism can result in a milder presentation that might only become evident in adulthood or during genetic testing for other reasons.
Lastly, some adults with muscular dystrophy-like symptoms might initially be misdiagnosed or their condition might have been undiagnosed in childhood due to atypical presentation or limited access to genetic testing. As diagnostic techniques improve, more adult cases are being identified, emphasizing the importance of genetic analysis for accurate diagnosis.
In summary, while Duchenne muscular dystrophy predominantly affects boys during childhood, adult cases do occur, either due to prolonged survival with medical support, genetic variations, new mutations, or atypical presentations. Understanding these causes helps in managing the disease better and highlights the importance of genetic counseling and testing for affected individuals and their families.
