Becker myotonia is a genetic condition that affects muscle function, characterized by delayed relaxation of muscles after contraction. It is caused by mutations in the CLCN1 gene, which is responsible for producing a protein that helps regulate chloride ions in muscle cells. This condition is a type of myotonia, which can lead to stiffness and difficulty in muscle movement, particularly after periods of rest. Symptoms of Becker myotonia typically appear in childhood or adolescence and may include muscle stiffness, weakness, and cramping. The severity of symptoms can vary among individuals. While there is no cure, management strategies such as physical therapy and medications can help alleviate symptoms and improve quality of life.