Proximal Myotonic Myopathies (PMM) are a group of rare, inherited muscular diseases characterized by muscle weakness and stiffness. These conditions fall under the umbrella term of myotonic disorders, which are caused by abnormalities in the way muscles relax and contract. PMM specifically affect the proximal muscles, which are the muscles closest to the center of the body, such as the hips, thighs, shoulders, and upper arms.
The most common forms of PMM are Myotonic Dystrophy Type 1 (DM1) and Myotonic Dystrophy Type 2 (DM2), which are caused by mutations in different genes. Both disorders are autosomal dominant, meaning that an affected individual has a 50% chance of passing the mutation on to their children. Symptoms of PMM may emerge at any age, but they commonly present in adulthood.
Clinical features of PMM typically include progressive muscle weakness, especially in the areas mentioned earlier, resulting in difficulties with walking, climbing stairs, lifting objects, and performing everyday activities. Stiffness of these muscles may also be experienced, making movements slow and cumbersome. Individuals with PMM may additionally exhibit myotonia, a condition characterized by delayed muscle relaxation after contraction.
Other potential symptoms may include cardiac abnormalities, respiratory issues, gastrointestinal problems, and cognitive impairments. Diagnosis of PMM involves a comprehensive evaluation of an individual's clinical history, observation of characteristic symptoms, and genetic testing to confirm the presence of the associated mutations.
Management of PMM typically involves a multidisciplinary approach, including physical therapy to maintain muscle strength and flexibility, assistive devices or mobility aids to compensate for muscle weaknesses, and medication to alleviate symptoms such as myotonia. Regular monitoring and intervention by healthcare professionals are essential to effectively manage the disease
