Myotonic Dystrophy
True cramps can occur in anyone, particularly after exercise or at night. Neuromuscular diseases in which classic cramps are common are amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy (SMA). A second kind of cramp, which doesn't involve abnormal nerve activity, occurs when a muscle is temporarily locked in a contracted state. This is technically called a contracture, but isn't to be confused with the more common use of "contracture" to indicate fixed joints. This sensation can be painful and is often described as a cramp. People with paramyotonia congenita, some forms of myotonia, rippling muscle syndrome or metabolic myopathies due to glycolytic defects (McArdle's disease, Cori's or Forbes' disease, Tarui's disease, phosphoglycerate kinase deficiency and lactate dehydrogenase deficiency) may experience muscle pain during exercise due to nonneural muscle cramps.
Definition - One of nine types of muscular dystrophy, a group of genetic, degenerative diseases primarily affecting voluntary muscles. Cause - A repeated section of DNA on either chromosome 19 or chromosome 3. Onset - Congenital form appears at birth. More common form may begin in teen or adult years. Symptoms - Generalized weakness and muscle wasting first affecting the face, lower legs, forearms, hands and neck, with delayed relaxation of muscles after contraction common. Other symptoms involve the gastrointestinal system, vision, heart or respiration. Learning disabilities occur in some cases. Congenital myotonic dystrophy is the more severe form. Progression -- Progression is slow, sometimes spanning 50 to 60 years. Inheritance - Autosomal dominant; the disease may be inherited through either the father or the mother.
Myotonia occurs when contracted muscles relax too slowly due to electrical problems in the muscle or nerve cells. A person with myotonia may have difficulty releasing his grip after holding an object - the sensation is sometimes described as stiffness. Myotonia can be sensitive to exercise, temperature or diet, and occurs in paramyotonia congenita (PC), myotonia congenita (MC), hyperkalemic periodic paralysis (PP) and myotonic dystrophy (MMD).
Fatigue can mean a subjective feeling of tiredness or an objective measurement of a decline in muscle force with use, but is always distinguished from weakness. Fatigue is associated with myasthenia gravis, ALS, SMA, myotonic disorders, metabolic disorders (McArdle's and Tarui's diseases) and mitochondrial disease. It can be a feature of many of the muscular dystrophies as muscles weaken and greater energy is expended to move them.