Causes
The genetic cause of ULD is known, but research has led to new areas of study that may lead to an increase in knowledge of what causes ULD. Genetic factors
The cause of ULD is known to be a mutation of the gene that produces cystatin B. The disease is autosomal recessive, so both parents of an individual must be carriers of the recessive CSTB gene for the individual to inherit it, and for an individual to show symptoms of ULD, they must have both recessive CSTB genes. Siblings of affected individuals who only have one recessive gene have been monitored and generally do not show the signs of ULD, though in some cases mild symptoms may be present. New developments
New research shows that cystatin B may not be the only factor involved in Unverricht–Lundborg disease. In a study, it was determined that patients with ULD had more dopamine receptors in certain areas of their brain than unaffected individuals. The researchers chose to investigate dopamine receptors because they are known to be a factor in myoclonus, which are a significant part of the symptoms of ULD. The results of this study indicate that the cause of ULD may be more complex than currently thought. Mechanism
While the genetic cause of Unverricht–Lundborg disease is known, the mechanism by which it works is not fully known. Current research has provided promising results that may lead to a confirmation of the mechanism.
Unverricht–Lundborg disease (abbreviated ULD or EPM1) is the most common form of an uncommon group of genetic epilepsy disorders called the progressive myoclonus epilepsies. It is caused due to a mutation in the cystatin B gene (CSTB). The disease is named after Heinrich Unverricht, who first described it in 1891, and Herman Bernhard Lundborg, who researched it in greater detail in 1901 and 1903. ULD onsets in children between the ages of 6 and 16; there are no known cases in which the person was older than 18. Most cases originate from the Baltic region of Europe, though many have been reported from countries in the Mediterranean.Onset of the disease is characterized by myoclonic jerks and tonic-clonic seizures. Early cases often resulted in the need of a wheelchair and death before the age of 24, but new treatments and medications have increased the life expectancy of individuals with ULD, in some cases even to near that of an unaffected individual. Signs and symptoms
Patients with Unverricht–Lundborg disease exhibit myoclonic jerks and tonic-clonic seizures at a young age, between ages 6–16. The myoclonic jerks occur in the muscles of the arms and legs closest to the torso, and are triggered due to a variety of common external stimuli. Seizures begin at an average age of 10.8 years, with myoclonus beginning around 12.1 years. It is not currently possible to diagnose without a genetic test, and since early symptoms are general, it is often mistaken for another more common epilepsy, in many cases juvenile myoclonic epilepsy (JME).