Thomsen disease, a form of Myotonia congenita

Myotonia congenita

Congenital myotonia is a genetic, neuromuscular channelopathy that affects skeletal muscles . It is congenital, meaning that it is present from birth. Amongst other problems, it causes delayed relaxation of the muscles and rigidity...

, is a muscular genetic disorder

Genetic disorder

A genetic disorder is an illness caused by abnormalities in genes or chromosomes, especially a condition that is present from before birth. Most genetic disorders are quite rare and affect one person in every several thousands or millions....

 characterized by muscle

Muscle

Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...

 stiffness (cramp

Cramp

Cramps are unpleasant, often painful sensations caused by muscle contraction or over shortening. Common causes of skeletal muscle cramps include muscle fatigue, low sodium, and low potassium...

) and an inability of the muscle to relax after a voluntary contraction. The affected muscle functions normally after a few repetitions.

Presentation

The disorder only affects voluntary muscles

Skeletal muscle

Skeletal muscle is a form of striated muscle tissue existing under control of the somatic nervous system- i.e. it is voluntarily controlled. It is one of three major muscle types, the others being cardiac and smooth muscle...

, so involuntary muscles

Smooth muscle

Smooth muscle is an involuntary non-striated muscle. It is divided into two sub-groups; the single-unit and multiunit smooth muscle. Within single-unit smooth muscle tissues, the autonomic nervous system innervates a single cell within a sheet or bundle and the action potential is propagated by...

 such as the heart

Heart

The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...

 or muscles involved in the digestion process are not affected.

Treatment and prognosis

There is no known cure but some drugs may relieve symptoms. These include: Dilantin, Procainamide

Procainamide

Procainamide INN is a pharmaceutical antiarrhythmic agent used for the medical treatment of cardiac arrhythmias, classified by the Vaughan Williams classification system as class Ia.-History:...

, Phenytoin

Phenytoin

Phenytoin sodium is a commonly used antiepileptic. Phenytoin acts to suppress the abnormal brain activity seen in seizure by reducing electrical conductance among brain cells by stabilizing the inactive state of voltage-gated sodium channels...

 and Mexiletine

Mexiletine

Mexiletine belongs to the Class IB anti-arrhythmic group of medicines. It is used to treat arrhythmias within the heart, or seriously irregular heartbeats. It slows conduction in the heart and makes the heart tissue less sensitive. Dizziness, heartburn, nausea, nervousness, trembling, unsteadiness...

.

The disease is not fatal but when the muscles tighten up, the person with MC can fall. What they fall on will determine the outcome of the fall.

History

Julius Thomsen, a Danish physician, was the first to describe the disease, citing symptoms of his own family members.