Myotonic muscular dystrophy (MMD), also known as Steinert’s disease, is a genetic disorder that affects the muscles and other systems in the body. It is one of the most common forms of muscular dystrophy in adults. Here is an overview of MMD:
1. Genetic cause: MMD is caused by an abnormal expansion of repetitive DNA sequences within the DMPK gene on chromosome 19. This genetic mutation disrupts the normal functioning of muscle cells and other tissues in the body.
2. Types of MMD: There are two main types of MMD: type 1 (MMD1) and type 2 (MMD2). MMD1 is more common and typically has an earlier onset and more severe symptoms compared to MMD2.
3. Symptoms: The symptoms of MMD can vary widely, even among affected individuals within the same family. Common symptoms may include muscle weakness and wasting, myotonia (prolonged muscle contractions), muscle stiffness, difficulty relaxing muscles after contraction, fatigue, and progressive difficulty with movement and coordination. MMD can also affect other body systems, leading to problems with the heart, respiratory system, gastrointestinal system, eyes, and endocrine system.
4. Age of onset: The age of onset for MMD can vary. In MMD1, symptoms typically appear in adolescence or adulthood, while in MMD2, symptoms often develop later in adulthood.
5. Diagnosis: MMD is diagnosed through a combination of physical examination, medical history, genetic testing, and electromyography (EMG) to assess muscle function. Genetic testing can confirm the presence of the abnormal DMPK gene expansion.
6. Management and treatment: There is no cure for MMD, and treatment focuses on managing symptoms and improving quality of life. This may involve a multidisciplinary approach with various healthcare specialists, including neurologists, physiotherapists, occupational therapists, speech and swallowing therapists, cardiologists, and respiratory specialists. Treatment options may include medications to manage symptoms, physical and occupational therapy to maintain muscle strength and function, assistive devices to aid mobility, and regular monitoring of heart and respiratory function.
It’s important for individuals with MMD to work closely with their healthcare team to develop a personalized management plan and receive ongoing support. Genetic counseling may also be recommended for affected individuals and their families to understand the inheritance pattern and make informed decisions about family planning.