Progressive myoclonic epilepsy type 1 (also called Unverricht-Lundborg disease or ULD) is a rare inherited form of epilepsy. Early development is normal in affected individuals. Signs and symptoms of the disorder typically begin between 6 and 15 years of age.

Variants (also called mutations) in the CSTB gene cause progressive myoclonic epilepsy type 1. The CSTB gene provides instructions for making a protein called cystatin B. This protein reduces the activity of enzymes called cathepsins. Cathepsins help break down certain proteins in the lysosomes, which are compartments in the cell that digest and recycle different types of molecules. While the specific function of cystatin B is unclear, it may help protect the cells' proteins from cathepsins that leak out of the lysosomes.

Progressive myoclonus epilepsy is a rare group of conditions.  Progressive myoclonic epilepsy type 1 is believed to be the most common form of this type of epilepsy, but its worldwide prevalence is unknown. The condition is more common in the North African countries of Tunisia, Algeria, and Morocco.  Progressive myoclonic epilepsy type 1 occurs most frequently in Finland, where approximately 2 in 100,000 people are affected.

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell must have a variant to cause the disorder. The parents of an individual with an autosomal recessive condition each carry one copy of the altered gene, but they typically do not show signs and symptoms of the condition.

Published Date: March 27, 2024
Published By: National Institutes of Health