Myotonia Congenita is a genetic disorder that affects muscle relaxation after contraction. Individuals with this condition experience prolonged muscle stiffness, particularly after periods of rest or inactivity. This stiffness can make movements, such as walking or grasping objects, challenging. The condition is caused by mutations in the CLCN1 gene, which is responsible for the function of chloride channels in muscle cells. Myotonia Congenita is often classified into two types: Thomsen disease, which is milder, and Becker myotonia, which is more severe. Diagnosis typically involves clinical evaluation and electromyography (EMG) tests.